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Alkaloids are a class of
basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer science deals with the theoretical foundations of information, algorithms and the ar ...
, naturally occurring
organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during ...
s that contain at least one
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
atom. This group also includes some related compounds with neutral and even weakly
acid An acid is a or capable of donating a (hydrogen ion H+) (a ), or, alternatively, capable of forming a with an (a ). The first category of acids are the proton donors, or s. In the special case of , proton donors form the H3O+ and are ...
ic properties. Some synthetic compounds of similar structure may also be termed alkaloids. In addition to
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
,
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
and
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
, alkaloids may also contain
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
,
sulfur Sulfur (in nontechnical British English: sulphur) is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: th ...

sulfur
and, more rarely, other elements such as
chlorine Chlorine is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemica ...

chlorine
,
bromine Bromine is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elemen ...

bromine
, and
phosphorus Phosphorus is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical el ...

phosphorus
.Chemical Encyclopedia: alkaloids
xumuk.ru
Alkaloids are produced by a large variety of organisms including
bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...

bacteria
,
fungi A fungus (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ...

fungi
,
plants Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel t ...

plants
, and
animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells ...

animal
s. They can be purified from crude extracts of these organisms by acid-base extraction, or solvent extractions followed by silica-gel
column chromatography Column chromatography in chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes ...

column chromatography
. Alkaloids have a wide range of
pharmacological Pharmacology is a branch of medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment or Palliative ...
activities including
antimalarial Antimalarial medications or simply antimalarials are a type of antiparasitic chemical agent, often naturally derived, that can be used to treat or to prevent malaria Malaria is a mosquito-borne infectious disease that affects humans and othe ...
(''e.g.''
quinine Quinine is a medication used to treat malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms Signs and symptoms are the observed or detectable signs, and experienced sympto ...

quinine
),
antiasthma
antiasthma
(''e.g.''
ephedrine Ephedrine is a medication and stimulant. It is often used to prevent low blood pressure during anesthesia Anesthesia or anaesthesia (from Greek "without sensation") is a state of controlled, temporary loss of sensation or awareness that is ...

ephedrine
),
anticancerAn anticarcinogen (also known as a carcinopreventive agent) is a substance that counteracts the effects of a carcinogen A carcinogen is any substance, radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is an ato ...

anticancer
(''e.g.''
homoharringtonine
homoharringtonine
),
cholinomimetic A parasympathomimetic drug, sometimes called a cholinomimetic drug or cholinergic receptor agonist, stimulating agent, is a substance that stimulates the parasympathetic nervous system (PSNS). These chemicals are also called cholinergic drugs becaus ...
(''e.g.''
galantamine Galantamine (sold under the brand name Razadyne and GalantaMind™) is used for the treatment of dementia, cognitive decline in mild to moderate Alzheimer's disease and various other memory impairments. It is an alkaloid that has been isolated from ...

galantamine
),
vasodilatory
vasodilatory
(''e.g.''
vincamine Vincamine is a monoterpenoid indole alkaloid Indole alkaloids are a class of alkaloids containing a Moiety (chemistry), structural moiety of indole; many indole alkaloids also include isoprene groups and are thus called terpene indole or secologani ...

vincamine
),
antiarrhythmic Antiarrhythmic agents, also known as cardiac dysrhythmia medications, are a group of pharmaceutical A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug File:Aspirine macro shot.jpg, Un ...
(''e.g.''
quinidine Quinidine is a medication that acts as a class I antiarrhythmic agent (Ia) in the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pum ...

quinidine
),
analgesic An analgesic or painkiller is any member of the group of used to achieve analgesia, relief from . They are distinct from s, which temporarily affect, and in some instances completely eliminate, . Analgesic choice is also determined by the type ...
(''e.g.''
morphine Morphine is a of the family that is found naturally in a dark brown, resinous form, from the poppy plant ('). It can be taken orally or injected. It acts directly on the (CNS) to induce analgesia and alter perception and emotional respons ...

morphine
),
antibacterial An antibiotic is a type of antimicrobial An antimicrobial is an agent that kills microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμ ...
(''e.g.''
chelerythrine
chelerythrine
), and
antihyperglycemic Drugs used in diabetes treat diabetes mellitus by altering the blood sugar level, glucose level in the blood. With the exceptions of Insulin (medication), insulin, exenatide, liraglutide and pramlintide, all are administered orally and are thus als ...
activities (''e.g.''
piperine Piperine, along with its isomer In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties ...
). Many have found use in
traditional A tradition is a belief A belief is an Attitude (psychology), attitude that something is the case, or that some proposition about the world is truth, true. In epistemology, philosophers use the term "belief" to refer to attitudes about the wo ...

traditional
or
modern medicine Medicine is the art Art is a diverse range of (products of) human activities involving creative imagination to express technical proficiency, beauty, emotional power, or conceptual ideas. There is no generally agreed definition of what ...
, or as starting points for
drug discovery In the fields of medicine, biotechnology Biotechnology is a broad area of biology, involving the use of living systems and organisms to develop or make products. Depending on the tools and applications, it often overlaps with related scientif ...
. Other alkaloids possess
psychotropic A psychoactive drug, psychopharmaceutical, or psychotropic drug is a chemical substance that changes nervous system In Biology, biology, the nervous system is a Complex system, highly complex part of an animal that coordinates its Behavior, ...
(''e.g.''
psilocin Psilocin (also known as 4-HO-DMT, 4-hydroxy DMT, psilocine, psilocyn, or psilotsin) is a substituted tryptamine alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of General-purpose p ...

psilocin
) and
stimulant Stimulants (also often referred to as psychostimulants or colloquially as uppers) is an overarching term that covers many drug Uncoated tablets, consisting of about 90% acetylsalicylic acid, along with a minor amount of inert fillers and b ...
activities (''e.g.''
cocaine Cocaine (from , from , ultimately from Quechuan languages, Quechua: ''kúka'') is a tropane alkaloid and stimulant drug obtained primarily from the leaves of two coca species native to South America, ''Erythroxylum coca'' and ''Erythroxylu ...

cocaine
,
caffeine Caffeine is a central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structu ...

caffeine
,
nicotine Nicotine is a naturally produced alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer sci ...

nicotine
,
theobromine Theobromine, also known as xantheose, is a bitter alkaloid Alkaloids are a class of base (chemistry), basic, natural product, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some relat ...

theobromine
), and have been used in entheogenic rituals or as
recreational drug Recreational drug use is the use of a psychoactive drug A psychoactive drug, psychopharmaceutical, psychoactive agent, or psychotropic drug, is a chemical substance that changes nervous system function and results in alterations in perception, ...
s. Alkaloids can be
toxic Toxicity is the degree to which a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects t ...

toxic
too (''e.g.''
atropine Atropine is a tropane alkaloid and anticholinergic medication used to treat certain types of nerve agent Nerve agents, sometimes also called nerve gases, are a class of organic chemicals that disrupt the mechanisms by which nerves transfer ...

atropine
,
tubocurarine Tubocurarine (also known as ''d''-tubocurarine or DTC) is a toxic alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of General-purpose programming language, general-purpose, high-leve ...

tubocurarine
). Although alkaloids act on a diversity of metabolic systems in humans and other animals, they almost uniformly evoke a bitter taste. The boundary between alkaloids and other nitrogen-containing natural compounds is not clear-cut.Robert A. Meyers ''Encyclopedia of Physical Science and Technology'' – Alkaloids, 3rd edition. Compounds like
amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, a ...

amino acid
peptide Peptides (from Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek (, ), refers collectively to the dialects of the Greek language spoken ...
s,
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
s,
nucleotide Nucleotides are organic molecules , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbon's ability to Catenation, ...

nucleotide
s,
nucleic acid Nucleic acids are biopolymer Biopolymers are natural polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material consisting of very large molecules, or macromolecule ...

nucleic acid
,
amine In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, ...

amine
s, and
antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy, ...
are usually not called alkaloids. Natural compounds containing nitrogen in the
exocyclic An alicyclic compound contains one or more all-carbon rings which may be either Saturated and unsaturated compounds, saturated or unsaturated, but do not have aromaticity, aromatic character. Alicyclic compounds may have one or more aliphatic side ...
position (
mescaline Mescaline (3,4,5-trimethoxyphenethylamine) is a naturally occurring psychedelic Psychedelics are a subset of hallucinogenic drugs whose primary effect is to trigger non-ordinary states of consciousness (known as psychedelic experience A ...

mescaline
,
serotonin Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter Monoamine neurotransmitters are s and s that contain one group connected to an by a two-carbon chain (such as -CH2-CH2-). Examples are , and . All monoamines are ...

serotonin
,
dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical , CH4; is among the simplest organic compounds. In chemistry Chemistry is t ...

dopamine
, etc.) are usually classified as
amine In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, ...

amine
s rather than as alkaloids. Some authors, however, consider alkaloids a special case of amines. Aniszewski, p. 110


Naming

The name "alkaloids" (german: Alkaloide, links=no) was introduced in 1819 by the German chemist Carl Friedrich Wilhelm Meißner, and is derived from late Latin root (which, in turn, comes from the Arabic meaning 'ashes of plants') and the suffix -('like'). In the penultimate sentence of his article, W. Meissner (1819) "Über Pflanzenalkalien: II. Über ein neues Pflanzenalkali (Alkaloid)" (On plant alkalis: II. On a new plant alkali (alkaloid)), ''Journal für Chemie und Physik'', 25 : 379–381 ; available on-line at:
Hathi Trust
– Meissner wrote: "." ( I. e, ''In general, it seems appropriate to me to impose on the currently known plant substances not the name "alkalis" but "alkaloids", since they differ greatly in some properties from the alkalis; among the chapters of plant chemistry, they would therefore find their place before plant acids ince "Alkaloid" would precede "Säure" (acid) but follow "Alkalien")
However, the term came into wide use only after the publication of a review article, by Oscar Jacobsen in the chemical dictionary of
Albert Ladenburg Albert Ladenburg (July 2, 1842August 15, 1911) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also ...

Albert Ladenburg
in the 1880s. There is no unique method for naming alkaloids.
Hesse Hesse (, , ) or Hessia (, ; german: Hessen ), officially the State of Hessen (german: links=no, Land Hessen), is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U. ...
, p. 5
Many individual names are formed by adding the suffix "ine" to the species or genus name. For example,
atropine Atropine is a tropane alkaloid and anticholinergic medication used to treat certain types of nerve agent Nerve agents, sometimes also called nerve gases, are a class of organic chemicals that disrupt the mechanisms by which nerves transfer ...

atropine
is isolated from the plant ''
Atropa belladonna ''Atropa belladonna'', commonly known as belladonna or deadly nightshade, is a poisonous perennial A perennial plant or simply perennial is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom ...
'';
strychnine Strychnine ( or ; ) is a highly toxicity, toxic, colorless, bitter, crystalline alkaloid used as a pesticide, particularly for killing small vertebrates such as birds and rodents. Strychnine, when inhaled, swallowed, or absorbed through the eyes ...

strychnine
is obtained from the seed of the Strychnine tree (''Strychnos nux-vomica'' L.). Where several alkaloids are extracted from one plant their names are often distinguished by variations in the suffix: "idine", "anine", "aline", "inine" etc. There are also at least 86 alkaloids whose names contain the root "vin" because they are extracted from ''
vinca ''Vinca'' (; Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Rom ...

vinca
'' plants such as ''Vinca rosea'' (''
Catharanthus roseus ''Catharanthus roseus'', commonly known as bright eyes, Cape periwinkle, graveyard plant, Madagascar periwinkle, old maid, pink periwinkle, rose periwinkle, is a species of flowering plant in the family Apocynaceae. It is native and endemism, end ...

Catharanthus roseus
''); these are called ''vinca'' alkaloids.


History

Alkaloid-containing plants have been used by humans since ancient times for therapeutic and recreational purposes. For example, medicinal plants have been known in
Mesopotamia Mesopotamia ( grc, Μεσοποταμία ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in th ...

Mesopotamia
from about 2000 BC. Aniszewski, p. 182 The ''
Odyssey The ''Odyssey'' (; grc, Ὀδύσσεια, Odýsseia, ) is one of two major ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí ...
'' of Homer referred to a gift given to Helen by the Egyptian queen, a drug bringing oblivion. It is believed that the gift was an opium-containing drug. A Chinese book on houseplants written in 1st–3rd centuries BC mentioned a medical use of
ephedra , an alkaloid found in ephedra Ephedra is a medicinal preparation from the plant '' Ephedra sinica''. Several additional species belonging to the genus ''Ephedra (genus), Ephedra'' have traditionally been used for a variety of medicinal purposes, ...

ephedra
and
opium poppies ''Papaver somniferum'', commonly known as the opium poppy or breadseed poppy, is a species of flowering plant in the family Papaveraceae. It is the species of plant from which both opium and poppy seeds are derived and is also a valuable ornamen ...
. Also,
coca Coca is any of the four cultivated plants in the family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-bei ...

coca
leaves have been used by South American Indians since ancient times. Extracts from plants containing toxic alkaloids, such as
aconitine Aconitine is an alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer science deals with th ...

aconitine
and
tubocurarine Tubocurarine (also known as ''d''-tubocurarine or DTC) is a toxic alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of General-purpose programming language, general-purpose, high-leve ...

tubocurarine
, were used since antiquity for poisoning arrows. Studies of alkaloids began in the 19th century. In 1804, the German chemist Friedrich Sertürner isolated from opium a "soporific principle" ( la, principium somniferum, links=no), which he called "morphium", referring to
Morpheus Morpheus ('Fashioner', derived from the grc, μορφή meaning 'form, shape') is a god associated with sleep Sleep is a naturally recurring state of mind and body, characterized by altered consciousness Consciousness, at its simp ...
, the Greek god of dreams; in German and some other Central-European languages, this is still the name of the drug. The term "morphine", used in English and French, was given by the French physicist
Joseph Louis Gay-Lussac Joseph Louis Gay-Lussac (, , ; 6 December 1778 – 9 May 1850) was a French chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin Medieval Latin was the form of Latin Latin (, or , ) ...

Joseph Louis Gay-Lussac
. A significant contribution to the chemistry of alkaloids in the early years of its development was made by the French researchers
Pierre Joseph Pelletier Pierre-Joseph Pelletier (, , ; 22 March 1788 – 19 July 1842) was a French chemist and pharmacist who did notable research on vegetable alkaloids, and was the co-discoverer with Joseph Bienaimé Caventou of quinine, caffeine, and strychnine. ...

Pierre Joseph Pelletier
and , who discovered
quinine Quinine is a medication used to treat malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms Signs and symptoms are the observed or detectable signs, and experienced sympto ...

quinine
(1820) and
strychnine Strychnine ( or ; ) is a highly toxicity, toxic, colorless, bitter, crystalline alkaloid used as a pesticide, particularly for killing small vertebrates such as birds and rodents. Strychnine, when inhaled, swallowed, or absorbed through the eyes ...

strychnine
(1818). Several other alkaloids were discovered around that time, including
xanthine Xanthine ( or ; archaically xanthic acid; systematic name 3,7-dihydropurine-2,6-dione) is a purine Purine is a heterocyclic compound, heterocyclic aromatic organic compound that consists of two rings (pyrimidine and imidazole). It is water-solubl ...

xanthine
(1817),
atropine Atropine is a tropane alkaloid and anticholinergic medication used to treat certain types of nerve agent Nerve agents, sometimes also called nerve gases, are a class of organic chemicals that disrupt the mechanisms by which nerves transfer ...

atropine
(1819),
caffeine Caffeine is a central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structu ...

caffeine
(1820), (1827),
nicotine Nicotine is a naturally produced alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer sci ...

nicotine
(1828),
colchicine Colchicine is a medication used to treat gout Gout is a form of inflammatory arthritisInflammatory arthritis is a group of diseases which includes: rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that ...

colchicine
(1833),
sparteine Sparteine is a class 1a antiarrhythmic agent Antiarrhythmic agents, also known as cardiac dysrhythmia medications, are a group of pharmaceuticals that are used to suppress abnormal rhythms of the heart (cardiac arrhythmias), such as atrial fibrill ...

sparteine
(1851), and
cocaine Cocaine (from , from , ultimately from Quechuan languages, Quechua: ''kúka'') is a tropane alkaloid and stimulant drug obtained primarily from the leaves of two coca species native to South America, ''Erythroxylum coca'' and ''Erythroxylu ...

cocaine
(1860). The development of the chemistry of alkaloids was accelerated by the emergence of
spectroscopic Spectroscopy is the study of the interaction between matter and Electromagnetism, electromagnetic radiation as a function of the wavelength or frequency of the radiation. In simpler terms, spectroscopy is the precise study of color as generalize ...
and
chromatographic In chemical analysis, chromatography is a laboratory technique for the Separation process, separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it t ...
methods in the 20th century, so that by 2008 more than 12,000 alkaloids had been identified. The first complete synthesis of an alkaloid was achieved in 1886 by the German chemist
Albert Ladenburg Albert Ladenburg (July 2, 1842August 15, 1911) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also ...

Albert Ladenburg
. He produced by reacting 2-methylpyridine with
acetaldehyde Ethanal (common name acetaldehyde) is an organic chemical compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds ...
and reducing the resulting 2-propenyl pyridine with sodium.


Classifications

Compared with most other classes of natural compounds, alkaloids are characterized by a great structural diversity. There is no uniform classification.
Hesse Hesse (, , ) or Hessia (, ; german: Hessen ), officially the State of Hessen (german: links=no, Land Hessen), is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U. ...
, p. 11
Initially, when knowledge of chemical structures was lacking, botanical classification of the source plants was relied on. This classification is now considered obsolete. More recent classifications are based on similarity of the carbon skeleton (''e.g.'',
indole Indole is an aromatic forms of benzene (top) combine to produce an average structure (bottom) In chemistry, aromaticity is a property of cyclic compound, cyclic (ring (chemistry), ring-shaped), plane (geometry), planar (flat) structures with p ...

indole
-,
isoquinoline Isoquinoline is a heterocyclic aromatic organic compound. It is a structural isomer of quinoline. Isoquinoline and quinoline are benzopyridines, which are composed of a benzene ring fused to a pyridine ring. In a broader sense, the term isoquino ...
-, and
pyridine Pyridine is a basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer science deals with the theoretical foundations of informati ...

pyridine
-like) or biochemical precursor (
ornithine Ornithine is a non-proteinogenic amino acid In biochemistry, non-coded or non-proteinogenic amino acids are distinct from the 22 proteinogenic amino acids (21 in eukaryotesplus formylmethionine in eukaryotes with prokaryote organelles like mitoch ...
,
lysine Lysine (symbol Lys or K) is an α-amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, ...

lysine
,
tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemi ...

tyrosine
,
tryptophan Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a non-polar Aromatic hydrocarbon, aromatic amino ...

tryptophan
, etc.). However, they require compromises in borderline cases; for example,
nicotine Nicotine is a naturally produced alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer sci ...

nicotine
contains a pyridine fragment from
nicotinamide Niacinamide or Nicotinamide (NAM) is a form of vitamin B3 found in food and used as a dietary supplement A dietary supplement is a manufactured product intended to supplement one's diet by taking a pill Pill or The Pill may refer t ...

nicotinamide
and a
pyrrolidine Pyrrolidine, also known as tetrahydropyrrole, is an organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to c ...

pyrrolidine
part from ornithine and therefore can be assigned to both classes. Dewick, p. 307 Alkaloids are often divided into the following major groups: # "True alkaloids" contain
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
in the
heterocycle 125px, Pyridine, a heterocyclic compound A heterocyclic compound or ring structure is a cyclic compound A cyclic compound (''ring compound'') is a term for a compound in the field of chemistry Chemistry is the scientific discipline invol ...
and originate from
amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, a ...

amino acid
s. Plemenkov, p. 223 Their characteristic examples are
atropine Atropine is a tropane alkaloid and anticholinergic medication used to treat certain types of nerve agent Nerve agents, sometimes also called nerve gases, are a class of organic chemicals that disrupt the mechanisms by which nerves transfer ...

atropine
,
nicotine Nicotine is a naturally produced alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer sci ...

nicotine
, and
morphine Morphine is a of the family that is found naturally in a dark brown, resinous form, from the poppy plant ('). It can be taken orally or injected. It acts directly on the (CNS) to induce analgesia and alter perception and emotional respons ...

morphine
. This group also includes some alkaloids that besides the nitrogen heterocycle contain terpene (''e.g.'', evonine) or peptide fragments (''e.g.'' ergotamine
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, p. 84
). The piperidine alkaloids and coniceine may be regarded as true alkaloids (rather than pseudoalkaloids: see below)
Hesse Hesse (, , ) or Hessia (, ; german: Hessen ), officially the State of Hessen (german: links=no, Land Hessen), is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U. ...
, p. 31
although they do not originate from amino acids. Dewick, p. 381 # "Protoalkaloids", which contain
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
(but not the nitrogen heterocycle) and also originate from amino acids. Examples include
mescaline Mescaline (3,4,5-trimethoxyphenethylamine) is a naturally occurring psychedelic Psychedelics are a subset of hallucinogenic drugs whose primary effect is to trigger non-ordinary states of consciousness (known as psychedelic experience A ...

mescaline
, adrenaline and
ephedrine Ephedrine is a medication and stimulant. It is often used to prevent low blood pressure during anesthesia Anesthesia or anaesthesia (from Greek "without sensation") is a state of controlled, temporary loss of sensation or awareness that is ...

ephedrine
. # Polyamine alkaloids – derivatives of putrescine, spermidine, and spermine. # Peptide and cyclopeptide alkaloids. # Pseudoalkaloids – alkaloid-like compounds that do not originate from amino acids. This group includes terpene-like and steroid-like alkaloids, as well as purine-like alkaloids such as
caffeine Caffeine is a central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structu ...

caffeine
,
theobromine Theobromine, also known as xantheose, is a bitter alkaloid Alkaloids are a class of base (chemistry), basic, natural product, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some relat ...

theobromine
, theacrine and theophylline. Aniszewski, p. 12 Some authors classify as pseudoalkaloids such compounds such as
ephedrine Ephedrine is a medication and stimulant. It is often used to prevent low blood pressure during anesthesia Anesthesia or anaesthesia (from Greek "without sensation") is a state of controlled, temporary loss of sensation or awareness that is ...

ephedrine
and cathinone. Those originate from the amino acid phenylalanine, but acquire their nitrogen atom not from the amino acid but through transamination. Dewick, p. 382 Some alkaloids do not have the carbon skeleton characteristic of their group. So, galanthamine and homoaporphines do not contain
isoquinoline Isoquinoline is a heterocyclic aromatic organic compound. It is a structural isomer of quinoline. Isoquinoline and quinoline are benzopyridines, which are composed of a benzene ring fused to a pyridine ring. In a broader sense, the term isoquino ...
fragment, but are, in general, attributed to isoquinoline alkaloids. Main classes of monomeric alkaloids are listed in the table below:


Properties

Most alkaloids contain oxygen in their molecular structure; those compounds are usually colorless crystals at ambient conditions. Oxygen-free alkaloids, such as
nicotine Nicotine is a naturally produced alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer sci ...

nicotine
or , are typically volatile, colorless, oily liquids.#Grinkevich, Grinkevich, p. 131 Some alkaloids are colored, like berberine (yellow) and sanguinarine (orange). Most alkaloids are weak bases, but some, such as
theobromine Theobromine, also known as xantheose, is a bitter alkaloid Alkaloids are a class of base (chemistry), basic, natural product, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some relat ...

theobromine
and theophylline, are amphoteric.G. A. Spille
''Caffeine''
CRC Press, 1997
Many alkaloids dissolve poorly in water but readily dissolve in organic solvents, such as diethyl ether, chloroform or 1,2-dichloroethane. Caffeine,
cocaine Cocaine (from , from , ultimately from Quechuan languages, Quechua: ''kúka'') is a tropane alkaloid and stimulant drug obtained primarily from the leaves of two coca species native to South America, ''Erythroxylum coca'' and ''Erythroxylu ...

cocaine
, codeine and
nicotine Nicotine is a naturally produced alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer sci ...

nicotine
are slightly soluble in water (with a solubility of ≥1g/L), whereas others, including
morphine Morphine is a of the family that is found naturally in a dark brown, resinous form, from the poppy plant ('). It can be taken orally or injected. It acts directly on the (CNS) to induce analgesia and alter perception and emotional respons ...

morphine
and yohimbine are very slightly water-soluble (0.1–1 g/L). Alkaloids and acids form salts of various strengths. These salts are usually freely soluble in water and ethanol and poorly soluble in most organic solvents. Exceptions include Hyoscine hydrobromide, scopolamine hydrobromide, which is soluble in organic solvents, and the water-soluble quinine sulfate. Most alkaloids have a bitter taste or are poisonous when ingested. Alkaloid production in plants appeared to have evolved in response to feeding by herbivorous animals; however, some animals have evolved the ability to detoxify alkaloids. Some alkaloids can produce developmental defects in the offspring of animals that consume but cannot detoxify the alkaloids. One example is the alkaloid cyclopamine, produced in the leaves of Veratrum californicum, corn lily. During the 1950s, up to 25% of lambs born by sheep that had grazed on corn lily had serious facial deformations. These ranged from deformed jaws to cyclopia (see picture). After decades of research, in the 1980s, the compound responsible for these deformities was identified as the alkaloid 11-deoxyjervine, later renamed to cyclopamine.


Distribution in nature

Alkaloids are anabolism, generated by various living organisms, especially by Vascular plant, higher plants – about 10 to 25% of those contain alkaloids. Therefore, in the past the term "alkaloid" was associated with plants.
Hesse Hesse (, , ) or Hessia (, ; german: Hessen ), officially the State of Hessen (german: links=no, Land Hessen), is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U. ...
, p.4
The alkaloids content in plants is usually within a few percent and is inhomogeneous over the plant tissues. Depending on the type of plants, the maximum concentration is observed in the leaves (black henbane), fruits or seeds ( Strychnine tree), root (''Rauvolfia serpentina'') or bark (cinchona). Furthermore, different tissues of the same plants may contain different alkaloids. Beside plants, alkaloids are found in certain types of fungi, such as psilocybin in the fungus of the genus ''Psilocybe'', and in animals, such as bufotenin in the skin of some toads and a number of insects, markedly ants. Many marine organisms also contain alkaloids. Some amines, such as adrenaline and
serotonin Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter Monoamine neurotransmitters are s and s that contain one group connected to an by a two-carbon chain (such as -CH2-CH2-). Examples are , and . All monoamines are ...

serotonin
, which play an important role in higher animals, are similar to alkaloids in their structure and biosynthesis and are sometimes called alkaloids.


Extraction

Because of the structural diversity of alkaloids, there is no single method of their extraction from natural raw materials.
Hesse Hesse (, , ) or Hessia (, ; german: Hessen ), officially the State of Hessen (german: links=no, Land Hessen), is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U. ...
, p. 116
Most methods exploit the property of most alkaloids to be soluble in organic solvents but not in water, and the opposite tendency of their salts. Most plants contain several alkaloids. Their mixture is extracted first and then individual alkaloids are separated.#Grinkevich, Grinkevich, p. 132 Plants are thoroughly ground before extraction. Most alkaloids are present in the raw plants in the form of salts of organic acids. The extracted alkaloids may remain salts or change into bases. Base extraction is achieved by processing the raw material with alkaline solutions and extracting the alkaloid bases with organic solvents, such as 1,2-dichloroethane, chloroform, diethyl ether or benzene. Then, the impurities are dissolved by weak acids; this converts alkaloid bases into salts that are washed away with water. If necessary, an aqueous solution of alkaloid salts is again made alkaline and treated with an organic solvent. The process is repeated until the desired purity is achieved. In the acidic extraction, the raw plant material is processed by a weak acidic solution (''e.g.'', acetic acid in water, ethanol, or methanol). A base is then added to convert alkaloids to basic forms that are extracted with organic solvent (if the extraction was performed with alcohol, it is removed first, and the remainder is dissolved in water). The solution is purified as described above. Alkaloids are separated from their mixture using their different solubility in certain solvents and different reactivity with certain reagents or by distillation. A number of alkaloids are identified from insects, among which the fire ant venom alkaloids known as solenopsins have received greater attention from researchers. These insect alkaloids can be efficiently extracted by solvent immersion of live fire ants or by centrifugation of live ants followed by silica-gel chromatography purification. Tracking and dosing the extracted solenopsin ant alkaloids has been described as possible based on their absorbance peak around 232 nanometers.


Biosynthesis

Biological precursors of most alkaloids are
amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, a ...

amino acid
s, such as
ornithine Ornithine is a non-proteinogenic amino acid In biochemistry, non-coded or non-proteinogenic amino acids are distinct from the 22 proteinogenic amino acids (21 in eukaryotesplus formylmethionine in eukaryotes with prokaryote organelles like mitoch ...
,
lysine Lysine (symbol Lys or K) is an α-amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, ...

lysine
, phenylalanine,
tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemi ...

tyrosine
,
tryptophan Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a non-polar Aromatic hydrocarbon, aromatic amino ...

tryptophan
, histidine, aspartic acid, and anthranilic acid. Plemenkov, p. 253 Nicotinic acid can be synthesized from tryptophan or aspartic acid. Ways of alkaloid biosynthesis are too numerous and cannot be easily classified. However, there are a few typical reactions involved in the biosynthesis of various classes of alkaloids, including synthesis of Schiff bases and Mannich reaction.


Synthesis of Schiff bases

Schiff bases can be obtained by reacting amines with ketones or aldehydes. These reactions are a common method of producing C=N bonds. Dewick, p. 19 In the biosynthesis of alkaloids, such reactions may take place within a molecule, such as in the synthesis of piperidine:


Mannich reaction

An integral component of the Mannich reaction, in addition to an amine and a carbonyl compound, is a carbanion, which plays the role of the nucleophile in the nucleophilic addition to the ion formed by the reaction of the amine and the carbonyl. The Mannich reaction can proceed both intermolecularly and intramolecularly:


Dimer alkaloids

In addition to the described above monomeric alkaloids, there are also Dimer (chemistry), dimeric, and even trimer (chemistry), trimeric and tetrameric alkaloids formed upon condensation of two, three, and four monomeric alkaloids. Dimeric alkaloids are usually formed from monomers of the same type through the following mechanisms: * Mannich reaction, resulting in, ''e.g.'', voacamine * Michael reaction (villalstonine) * Condensation of aldehydes with amines (toxiferine) * Oxidative addition of phenols (dauricine, tubocurarine) * Lactone, Lactonization (carpaine). File:Voacamine chemical structure.png, Voacamine File:Villalstonine.svg, Villalstonine File:Toxiferine I.png, Toxiferine File:Dauricine.svg, Dauricine File:Tubocurarine.svg, Tubocurarine File:Carpaine.png, Carpaine There are also dimeric alkaloids formed from two distinct monomers, such as the ''vinca'' alkaloids vinblastine and vincristine, which are formed from the coupling of catharanthine and vindoline. The newer semisynthesis, semi-synthetic chemotherapeutic agent vinorelbine is used in the treatment of non-small-cell lung cancer. It is another derivative dimer of vindoline and catharanthine and is synthesised from anhydrovinblastine, starting either from leurosine or the monomers themselves.


Biological role

The role of alkaloids for living organisms that produce them is still unclear. It was initially assumed that the alkaloids are the final products of
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
metabolism in plants, as urea in mammals. It was later shown that alkaloid concentration varies over time, and this hypothesis was refuted. A number of ants are suggested to also produce alkaloids as venom components, however the exact biosynthesis pathways have not been empirically demonstrated. Most of the known functions of alkaloids are related to protection. For example, aporphine alkaloid liriodenine produced by the Liriodendron tulipifera, tulip tree protects it from parasitic mushrooms. In addition, the presence of alkaloids in the plant prevents insects and chordate animals from eating it. However, some animals are adapted to alkaloids and even use them in their own metabolism. Such alkaloid-related substances as
serotonin Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter Monoamine neurotransmitters are s and s that contain one group connected to an by a two-carbon chain (such as -CH2-CH2-). Examples are , and . All monoamines are ...

serotonin
,
dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical , CH4; is among the simplest organic compounds. In chemistry Chemistry is t ...

dopamine
and histamine are important neurotransmitters in animals. Alkaloids are also known to regulate plant growth. One example of an organism that uses alkaloids for protection is the ''Utetheisa ornatrix'', more commonly known as the ornate moth. Pyrrolizidine alkaloids render these larvae and adult moths unpalatable to many of their natural enemies like coccinelid beetles, green lacewings, insectivorous hemiptera and insectivorous bats. Another example of alkaloids being utilized occurs in the Agonopterix alstroemeriana, poison hemlock moth (''Agonopterix alstroemeriana).'' This moth feeds on its highly toxic and alkaloid-rich host plant Conium maculatum, poison hemlock (''Conium maculatum'') during its larval stage. ''A. asltroemeriana'' may benefit twofold from the toxicity of the naturally-occurring alkaloids, both through the unpalatability of the species to predators and through the ability of ''A. alstroemeriana'' to recognize ''Conium maculatum'' as the correct location for oviposition. A fire ant venom alkaloid known as solenopsin has been demonstrated to protect queens of Red imported fire ant, invasive fire ants during the foundation of new nests, thus playing a central role in the spread of this pest ant species around the world.


Applications


In medicine

Medical use of alkaloid-containing plants has a long history, and, thus, when the first alkaloids were isolated in the 19th century, they immediately found application in clinical practice. Many alkaloids are still used in medicine, usually in the form of salts widely used including the following: Many synthetic and semisynthetic drugs are structural modifications of the alkaloids, which were designed to enhance or change the primary effect of the drug and reduce unwanted side-effects. For example, naloxone, an opioid receptor receptor antagonist, antagonist, is a derivative of thebaine that is present in opium. File:Thebaine skeletal.svg, Thebaine File:Naloxone.svg, Naloxone


In agriculture

Prior to the development of a wide range of relatively low-toxic synthetic pesticides, some alkaloids, such as salts of nicotine and anabasine, were used as insecticides. Their use was limited by their high toxicity to humans.


Use as psychoactive drugs

Preparations of plants containing alkaloids and their extracts, and later pure alkaloids, have long been used as Psychoactive drug, psychoactive substances. Cocaine,
caffeine Caffeine is a central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structu ...

caffeine
, and cathinone are
stimulant Stimulants (also often referred to as psychostimulants or colloquially as uppers) is an overarching term that covers many drug Uncoated tablets, consisting of about 90% acetylsalicylic acid, along with a minor amount of inert fillers and b ...
s of the central nervous system. Mescaline and many indole alkaloids (such as psilocybin, dimethyltryptamine and ibogaine) have hallucinogenic effect. Morphine and codeine are strong narcotic pain killers. There are alkaloids that do not have strong psychoactive effect themselves, but are precursor (chemistry), precursors for semi-synthetic psychoactive drugs. For example,
ephedrine Ephedrine is a medication and stimulant. It is often used to prevent low blood pressure during anesthesia Anesthesia or anaesthesia (from Greek "without sensation") is a state of controlled, temporary loss of sensation or awareness that is ...

ephedrine
and pseudoephedrine are used to produce methcathinone and methamphetamine.#Veselovskaya, Veselovskaya, pp. 51–52 Thebaine is used in the synthesis of many painkillers such as oxycodone.


See also

* Amine * Base (chemistry) * List of poisonous plants * Natural products * Palau'amine * Secondary metabolite * Mayer's reagent


Notes


References


Bibliography

* * * * * * * * * * * * * {{Authority control Alkaloids, *