Propolis or bee glue is a

resin In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on natu ...

ous mixture that

honey bee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current co ...

s produce by mixing saliva and

beeswax Beeswax (''cera alba'') is a natural wax produced by honey bees of the genus ''Apis''. The wax is formed into scales by eight wax-producing glands in the abdominal segments of worker bees, which discard it in or at the hive. The hive workers ...

with

exudate An exudate is a fluid emitted by an organism through pores or a wound, a process known as exuding or exudation. ''Exudate'' is derived from ''exude'' 'to ooze' from Latin ''exsūdāre'' 'to (ooze out) sweat' (''ex-'' 'out' and ''sūdāre'' 'to ...

gathered from tree buds, sap flows, or other botanical sources. It is used as a sealant for unwanted open spaces in the

beehive A beehive is an enclosed structure in which some honey bee species of the subgenus '' Apis'' live and raise their young. Though the word ''beehive'' is commonly used to describe the nest of any bee colony, scientific and professional literature ...

. Propolis is used for small gaps (approximately or less), while gaps larger than the

bee space Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the super ...

(approximately ) are usually filled with

burr comb In beekeeping, in a Langstroth hive, burr comb, also known as brace comb and bridge comb, are portions of honeycomb built by the bees in other places than in the intended place in the frames. Burr comb is commonly found on the top of frames, parti ...

. Its color varies depending on its botanical source, with dark

brown Brown is a color. It can be considered a composite color, but it is mainly a darker shade of orange. In the CMYK color model used in printing or painting, brown is usually made by combining the colors orange and black. In the RGB color model used ...

as the most common. Propolis is sticky at and above , while at lower temperatures it becomes hard and brittle. When foraging, worker bees primarily harvest pollen and nectar, while also collecting water and plant resin necessary for the production of propolis. The chemical composition and nature of propolis depend on environmental conditions and harvested resources.

Types

Mixed types of propolis found in European countries with a moderate climate include two or more sources of plant resins (plant species) identified by composition, such as

aspen Aspen is a common name for certain tree species; some, but not all, are classified by botanists in the section ''Populus'', of the ''Populus'' genus. Species These species are called aspens: *'' Populus adenopoda'' – Chinese aspen (China ...

, Mediterranean, poplar, Pacific, Brazilian green, Brazilian red, and

Mangifera ''Mangifera'' is a genus of flowering plants in the cashew family, Anacardiaceae. It contains approximately 69 species, with the best-known being the Common Mango (''Mangifera indica''). The center of diversity of the genus is in the Malesian ec ...

types of propolis.

Purpose

Bees seal the beehive with propolis to protect the colony from the elements, such as rain and cold winter drafts. Propolis functions may include: #Reinforce the structural stability and reduce vibration #Provide improved

thermal insulation Thermal insulation is the reduction of heat transfer (i.e., the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with s ...

to the hive and reduce water loss #Provides protection from pathogens, via anti-fungal and antibacterial properties #Make the hive more defensible against parasites and predators by narrowing the existing entrance (in wild colonies) to a single "choke point" #Mitigate

putrefaction Putrefaction is the fifth stage of death, following pallor mortis, algor mortis, rigor mortis, and livor mortis. This process references the breaking down of a body of an animal, such as a human, post-mortem. In broad terms, it can be viewed ...

within the hive. Bees usually carry waste out of and away from the hive. However, if a small

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

mouse A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

, for example, finds its way into the hive and dies there, bees may be unable to carry it out through the hive entrance. In that case, they would attempt instead to seal the

carcass Carcass or Carcase (both pronounced ) may refer to: *Dressed carcass, the body of a livestock animal ready for butchery, after removal of skin, visceral organs, head, feet etc. *Carrion, the decaying dead body of an animal or human being *The str ...

in propolis, essentially mummifying it and making it odorless and harmless.

Composition

The composition of propolis varies from hive to hive, from district to district, and from season to season. Normally, it is dark brown in color, but it can be found in green, red, black, and white hues, depending on the sources of resin found in the particular hive area. Honey bees are opportunists, gathering what they need from available sources, and detailed analyses show that the chemical composition of propolis varies considerably from region to region, along with the vegetation. In northern

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

climates, for example, bees collect resins from

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

s, such as

poplars ''Populus'' is a genus of 25–30 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar (), aspen, and cottonwood. The we ...

and

conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single ...

s (the biological role of resin in trees is to seal wounds and defend against bacteria, fungi, and insects). "Typical" northern temperate propolis has approximately 50 constituents, primarily resins and vegetable

balsam Balsam is the resinous exudate (or sap) which forms on certain kinds of trees and shrubs. Balsam (from Latin balsamum "gum of the balsam tree", ultimately from Semitic, Aramaic ''busma'', Arabic ''balsam'' and Hebrew ''basam'', "spice", "perfume ...

s (50%),

wax Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to giv ...

es (30%),

essential oil An essential oil is a concentrated hydrophobic liquid containing volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetheroleum, or simply as the o ...

s (10%), and

pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...

(5%). An analysis of propolis from

Henan Henan (; or ; ; alternatively Honan) is a landlocked province of China, in the central part of the country. Henan is often referred to as Zhongyuan or Zhongzhou (), which literally means "central plain" or "midland", although the name is al ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

found

sinapinic acid Sinapinic acid, or sinapic acid (Sinapine - Origin: L. Sinapi, sinapis, mustard, Gr., cf. F. Sinapine.), is a small naturally occurring hydroxycinnamic acid. It is a member of the phenylpropanoid family. It is a commonly used matrix in MALDI mass ...

isoferulic acid Isoferulic acid is a hydroxycinnamic acid, a type of organic compound. It is an isomer of ferulic acid. Occurrence in nature Isoferulic acid can be found, amongst other compounds, in ''Lobelia chinensis''. In food Ferulic acid is found in pin ...

caffeic acid Caffeic acid is an organic compound that is classified as a hydroxycinnamic acid. This yellow solid consists of both phenolic and acrylic functional groups. It is found in all plants because it is an intermediate in the biosynthesis of lignin, one ...

, and chrysin. In

neotropical The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In bioge ...

regions, in addition to a large variety of trees, bees may also gather resin from flowers in the genera ''

Clusia ''Clusia'' is the type genus of the plant family Clusiaceae. Comprising 300-400 species, it is native to the tropics of the Americas. The genus is named by Carl Linnaeus in honor of the botanist Carolus Clusius. The closest relatives of ''Clus ...

'' and ''

Dalechampia ''Dalechampia'' is a genus of plant of the family Euphorbiaceae and of the monogeneric subtribe Dalechampiinae. It is widespread across lowland tropical areas (generally below 2,000 m ASL) primarily in the Americas with smaller numbers of spec ...

'', which are the only known plant genera that produce floral resins to attract pollinators. ''Clusia'' resin contains polyprenylated benzophenones. In some areas of

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

and

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

Andean valleys, propolis contains viscidone, a

terpene Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n > 1. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. Terpenes ar ...

from ''

Baccharis ''Baccharis'' is a genus of perennials and shrubs in the aster family (Asteraceae). They are commonly known as baccharises but sometimes referred to as "brooms", because many members have small thin leaves resembling the true brooms. They are n ...

'' shrubs, and prenylated acids, such as 4-hydroxy-3,5-diprenyl cinnamic acid. Overall,

flavonoid Flavonoids (or bioflavonoids; from the Latin word ''flavus'', meaning yellow, their color in nature) are a class of polyphenolic secondary metabolites found in plants, and thus commonly consumed in the diets of humans. Chemically, flavonoids ...

phenolic acid Phenolic acids or phenolcarboxylic acids are types of aromatic acid compounds. Included in that class are substances containing a phenolic ring and an organic carboxylic acid function (C6-C1 skeleton). Two important naturally occurring types of ...

s, and

phenolic aldehyde Phenolic aldehydes are derivatives of phenol. Phenolic aldehydes can be found in wines and cognacs. Examples : * Hydroxybenzaldehydes * Protocatechuic aldehyde * Vanillin and isovanillin Isovanillin is a phenolic aldehyde, an organic compound an ...

s are common constituents, while

coumarin Coumarin () or 2''H''-chromen-2-one is an aromatic organic chemical compound with formula . Its molecule can be described as a benzene molecule with two adjacent hydrogen atoms replaced by a lactone-like chain , forming a second six-membered h ...

stilbene Stilbene may refer to one of the two stereoisomers of 1,2-diphenylethene: * (''E'')-Stilbene (''trans'' isomer) * (''Z'')-Stilbene (''cis'' isomer) See also * Stilbenoids, a class of molecules found in plants * 1,1-Diphenylethylene 1,1-Diphenyl ...

s, and

lignan The lignans are a large group of low molecular weight polyphenols found in plants, particularly seeds, whole grains, and vegetables. The name derives from the Latin word for "wood". Lignans are precursors to phytoestrogens. They may play a role ...

s are less common.

Traditional medicine

Propolis has been used in

traditional medicine Traditional medicine (also known as indigenous medicine or folk medicine) comprises medical aspects of traditional knowledge that developed over generations within the folk beliefs of various societies, including indigenous peoples, before the ...

, with insufficient evidence to rate its effectiveness in the treatment of any illnesses.

Other uses

Musical instruments

Propolis is used by some string instrument makers (violin, viola, cello, and bass) as a

varnish Varnish is a clear transparent hard protective coating or film. It is not a stain. It usually has a yellowish shade from the manufacturing process and materials used, but it may also be pigmented as desired, and is sold commercially in various ...

ingredient. A tincture of propolis may be used to seal the surface of newly made violin family

bridges A bridge is a structure built to Span (engineering), span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, whic ...

, and may be used in the maintenance of the bores of

pan flute A pan flute (also known as panpipes or syrinx) is a musical instrument based on the principle of the closed tube, consisting of multiple pipes of gradually increasing length (and occasionally girth). Multiple varieties of pan flutes have been ...

tubes. Claims that

Antonio Stradivari Antonio Stradivari (, also , ; – 18 December 1737) was an Italian luthier and a craftsman of string instruments such as violins, cellos, guitars, violas and harps. The Latinized form of his surname, ''Stradivarius'', as well as the colloq ...

used propolis in the varnish of his instruments were disproven in 2009.Secret behind the composition of the varnish on Stradivari violins revealed
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References

External links

* {{Authority control Beekeeping Bee products Traditional medicine Xanthine oxidase inhibitors