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''Siraitia grosvenorii'', also known as monkfruit or ''luohan guo'', is a
herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of t ...
perennial vine of the gourd family, Cucurbitaceae. It is native to southern China. The plant is cultivated for its fruit
extract An extract is a substance made by extracting a part of a raw material, often by using a solvent such as ethanol, oil or water. Extracts may be sold as tinctures, absolutes or in powder form. The aromatic principles of many spices, nuts, h ...
, called mogrosides, which creates a
sweetness Sweetness is a Taste#Basic tastes, basic taste most commonly Perception, perceived when eating foods rich in sugars. Sweet tastes are generally regarded as pleasure, pleasurable. In addition to sugars like sucrose, many other chemical compounds ...
sensation 250 times stronger than
sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined ...
. Mogroside extract has been used as a low-
calorie The calorie is a unit of energy. For historical reasons, two main definitions of "calorie" are in wide use. The large calorie, food calorie, or kilogram calorie was originally defined as the amount of heat needed to raise the temperature of on ...
sweetener for drinks and in traditional Chinese medicine. The scientific species name honors Gilbert Hovey Grosvenor, who, as president of the National Geographic Society, helped to fund an expedition in the 1930s to find the living plant in China where it was already being cultivated.


Etymology and regional names

The fruit was first mentioned in the records of 13th-century Chinese monks in
Guangxi Guangxi (; ; Chinese postal romanization, alternately romanized as Kwanghsi; ; za, Gvangjsih, italics=yes), officially the Guangxi Zhuang Autonomous Region (GZAR), is an Autonomous regions of China, autonomous region of the People's Republic ...
in the region of Guilin. The difficulty of cultivation meant the fruit did not become part of the Chinese herbal tradition which depended on more readily available products. ''Luóhàn'' (羅漢) is a shortened form of ''āluóhàn'' (), which is an old transliteration of the Indian Sanskrit word '' arhat'' ( prakrit: ''arahant''). In early Buddhist traditions, a monk who becomes enlightened is called an '' arhat'' who attains the "fruition of arhatship" (Sanskrit: ''arhattaphala''). This was rendered in Chinese as ''luóhàn guǒ'' (羅漢果 literally "arhat fruit") which later became the Chinese and western commercial designation for this type of sweet fruit. It may also be called ''la han qua'' (from Vietnamese ''la hán quả'', which also means Arhat fruit), or longevity fruit (also used for other fruits).Ling Yeouruenn, ''A New Compendium of Materia Medica'', 1995 Science Press, Beijing


History and distribution

The first report in England on the herb was found in an unpublished manuscript written in 1938 by G. Weidman Groff and Hoh Hin Cheung. The report stated the fruits were often used as the main ingredients of "cooling drinks" as remedies for hot weather, fever, or other dysfunctions traditionally associated with warmth or heat (e.g., inflammation). The fruit was taken to the United States in the early 20th century. Groff mentioned that, during a visit to the American ministry of agriculture in 1917, the botanist Frederick Coville showed him a ''luo han guo'' fruit bought in a Chinese shop in Washington, DC. Seeds of the fruit, which had been bought in a Chinese shop in San Francisco, were entered into the botanic description of the species in 1941. The first research into the sweet component of ''luo han guo'' is attributed to C. H. Lee, who wrote an English report on it in 1975, and also to Tsunematsu Takemoto, who worked on it the early 1980s in Japan (later Takemoto decided to concentrate on the similar sweet plant, ''
jiaogulan ''Gynostemma pentaphyllum'', also called jiaogulan (, Pinyin: jiǎogǔlán, literally "twisting blue plant"), is a dioecious, herbaceous climbing vine of the family Cucurbitaceae (cucumber or gourd family) widely distributed in South and East A ...
''). The development of ''luo han guo'' products in China has continued ever since, focusing in particular on the development of concentrated extracts.


Description

The vine attains a length of 3 to 5 m, climbing over other plants by means of tendrils which twine around anything they touch. The narrow, heart-shaped
leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
are 10–20 cm long. The fruit is round, 5–7 cm in diameter, smooth, yellow-brownish or green-brownish in color, containing striations from the fruit stem end of the furrows with a hard but thin skin covered by fine hairs. The inside of the fruit contains an edible pulp, which, when dried, forms a thin, light brown, brittle shell about 1 mm in thickness. The seeds are elongated and almost spherical. The interior fruit is eaten fresh, and the rind is used to make tea. The monk fruit is notable for its sweetness, which can be concentrated from its juice. The fruit contains 25 to 38% of various carbohydrates, mainly
fructose Fructose, or fruit sugar, is a Ketose, ketonic monosaccharide, simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galacto ...
and glucose. The sweetness of the fruit is increased by the mogrosides, a group of triterpene glycosides (saponins). The five different mogrosides are numbered from I to V; the main component is mogroside V, which is also known as esgoside.


Mogroside biosynthesis

One analysis of 200 candidate genes of ''Siraitia grosvenorii'' revealed five enzyme families involved in the synthesis of mogroside V: squalene epoxidases,
triterpenoid Triterpenes are a class of chemical compounds composed of three terpene units with the molecular formula C30H48; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi all produce triterpenes, including squale ...
synthase In biochemistry, a synthase is an enzyme that catalyses a synthesis process. Note that, originally, biochemical nomenclature distinguished synthetases and synthases. Under the original definition, synthases do not use energy from nucleoside tripho ...
s, epoxide hydrolases,
cytochrome P450 Cytochromes P450 (CYPs) are a Protein superfamily, superfamily of enzymes containing heme as a cofactor (biochemistry), cofactor that functions as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are ...
s, and UDP- glucosyltransferases. The metabolic pathway for mogroside biosynthesis involves an initial stage of fruit development when squalene is metabolized to di-glucosylated, tetra-hydroxycucurbitadienols, then during fruit maturation, branched
glucosyl A glycosyl group is a univalent free radical or substituent structure obtained by removing the hemiacetal hydroxyl group from the cyclic form of a monosaccharide and, by extension, of a lower oligosaccharide. Glycosyl also reacts with inorganic a ...
groups are added and catalyzed, leading to the sweet M4, M5, and M6 mogrosides.


Cultivation

Germination of seeds is slow and may take several months. It is grown primarily in the far southern Chinese province of
Guangxi Guangxi (; ; Chinese postal romanization, alternately romanized as Kwanghsi; ; za, Gvangjsih, italics=yes), officially the Guangxi Zhuang Autonomous Region (GZAR), is an Autonomous regions of China, autonomous region of the People's Republic ...
(mostly in the mountains near Guilin), as well as in Guangdong, Guizhou, Hunan, and Jiangxi. These mountains lend the plants shade and often are surrounded by mists which protect the plants from the sun. Nonetheless, the climate in this southern province is warm. The plant is rarely found in the wild, so it has been cultivated for hundreds of years. Records as early as 1813 mention the cultivation of this plant in the Guangxi province. Most of the plantations are located in Yongfu County and Lingui County. Longjiang Town in Yongfu County has acquired the name "home of the Chinese ''luohanguo'' fruit"; a number of companies specialised in making ''luohanguo'' extracts and finished products have been set up in the area. The Yongfu Pharmaceutical Factory is the oldest of these.


Traditional processing

''Luohan guo'' is harvested in the form of a round, green fruit, which becomes brown on drying. It is rarely used in its fresh form, as it is hard to store when fresh. Thus, the fruits are usually dried before further use and are sold in this fashion in Chinese herbal shops. The fruits are dried slowly in ovens, preserving them and removing most of the unwanted aromas. However, this technique also leads to the formation of several bitter and astringent flavors. This limits the use of the dried fruits and extracts to the preparation of diluted tea, soup, and as a sweetener for products that would usually have sugar or
honey Honey is a sweet and viscous substance made by several bees, the best-known of which are honey bees. Honey is made and stored to nourish bee colonies. Bees produce honey by gathering and then refining the sugary secretions of plants (primar ...
added to them.


Commercial manufacturing

The process for the manufacture of a useful sweetener from ''luo han guo'' was patented in 1995 by Procter & Gamble. The patent states that ''luo han guo'' has many interfering flavors, which render it useless for general applications, and describes a process to remove them. The offending compounds are
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
-containing volatile substances such as
hydrogen disulfide Hydrogen disulfide is the inorganic compound with the formula H2S2. This hydrogen chalcogenide is a pale yellow volatile liquid with a camphor-like odor. It decomposes readily to hydrogen sulfide (H2S) and elemental sulfur.R. Steudel "Inorgani ...
, methional,
methionol Methionol (3-(Methylthio)-1-propanol) is a methyl sulfide derived from propan-1-ol. It is found in nature, including as a metabolite of yeast and bacillus anthracis. It is a sulphurous aroma An odor (American English) or odour (Commonwealt ...
, dimethylsulfide, and
methylmercaptan Methanethiol (also known as methyl mercaptan) is an organosulfur compound with the chemical formula . It is a colorless gas with a distinctive putrid smell. It is a natural substance found in the blood, brain and feces of animals (including humans ...
, which are formed from amino acids that contain
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
, such as
methionine Methionine (symbol Met or M) () is an essential amino acid in humans. As the precursor of other amino acids such as cysteine and taurine, versatile compounds such as SAM-e, and the important antioxidant glutathione, methionine plays a critical ro ...
, S-methylmethionine, cystine, and
cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, sometime ...
.


Sweetening agent

The sweet taste of the fruit comes mainly from mogrosides, a group of triterpene
glycosides In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...
that make up about 1% of the flesh of the fresh fruit. Through solvent extraction, a powder containing 80% mogrosides can be obtained, the main one being mogroside-5 (esgoside). Other similar agents in the fruit are siamenoside and neomogroside. In this process, the peel and seeds are removed, and the pulped fruit is made into a fruit concentrate or puree. Additional juice may be extracted from the remaining pulp by hot water. The juice is homogenized, acidified slightly to prevent
gel A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state, although the liquid phase may still di ...
ling and improve the flavor, then treated with
pectinase Pectinases are a group of enzymes that breaks down pectin, a polysaccharide found in plant cell walls, through hydrolysis, transelimination and deesterification reactions. Commonly referred to as pectic enzymes, they include pectolyase, pectozym ...
or other enzymes to break down the
pectin Pectin ( grc, πηκτικός ': "congealed" and "curdled") is a heteropolysaccharide, a structural acid contained in the primary lamella, in the middle lamella, and in the cell walls of terrestrial plants. The principal, chemical component of ...
. Most of the off-flavor agents are then removed with ion-exchange resins, such as
sulfonated Aromatic sulfonation is an organic reaction in which a hydrogen atom on an arene is replaced by a sulfonic acid functional group in an electrophilic aromatic substitution. Aryl sulfonic acids are used as detergents, dye, and drugs. Stoichiomet ...
polystyrene-divinylbenzene copolymer or
polyacrylic acid Poly(acrylic acid) (PAA; trade name Carbomer) is a polymer with the formula (CH2-CHCO2H)n. It is a derivative of acrylic acid (CH2=CHCO2H). In addition to the homopolymers, a variety of copolymers and crosslinked polymers, and partially deproto ...
. Alternatively, the off-flavors can be adsorbed by agents like
charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, cal ...
or bentonite, which are removed by filtration; or precipitated with
gelatin Gelatin or gelatine (from la, gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also ...
or other gelling agents. Most of the remaining sulfurous volatiles are then removed by low- pressure
evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...
. The juice is then pasteurized to inactivate remaining natural enzymes and kill micro-organisms. The process is claimed to preserve a substantial fraction of the mogrosides present in the fruit, with the resulting sweetness at a level about 250 times stronger than sucrose.


Safety

At least one generally recognized as safe (GRAS) notice has been received by the U.S. Food and Drug Administration. In Europe, it is classified as an unapproved Novel Food (not used in the
food system The term food system describes the interconnected systems and processes that influence nutrition Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It provides organisms with nutrients ...
before May 1997) which means that it may be marketed as a food or food ingredient only after a safety assessment and approval by the European Commission; as of 2020, ''Siraitia grosvenorii'' was not listed among approved Novel Foods in the EU.


Traditional uses

The plant is most prized for its sweet fruits as a sweetener. In traditional Chinese medicine, it is used for cough and sore throat. The fruits are generally sold in dried form, and used in herbal tea or soup.


References


External links

* * {{Taxonbar, from=Q1544966 Cucurbitoideae Fruits originating in Asia Flora of China Crops originating from China Plants used in traditional Chinese medicine Dietary supplements Sugar substitutes Tropical fruit