Luo Han Guo (Monk Fruit) (Siraitia grosvenorii, Cucurbitaceae)
by Gayle Engels, Josef Brinckmann
HerbalGram. 2014; American Botanical Council
Siraitia grosvenorii is a vining perennial in the cucumber/melon/gourd family (Cucurbitaceae).1 It grows from six to 16 feet (two to five meters) tall via clinging tendrils and has both male and female flowers in early summer,2 followed by dark green fruit that turns brown when dried.3 Also called monk fruit, luo han guo (or luohanguo) is the fruit of this vine; the leaf is referred to as luo han ye.1 Unless stated otherwise, all the information in this article refers to the fruit.
While it can be found growing in forests, on mountain slopes, riversides, and thickets in the Chinese provinces of Guangdong, Guangxi, Guizhou, Hunan, and Jiangxi,4 it is rare in the wild and has been cultivated in Guangxi for many years.3,5 Triterpene glycosides called mogrosides are the primary active chemical constituents in luo han guo, and the content of mogroside V in the fruits has been shown to be about 50% higher when grown in south Guangxi compared to yields in north Guangxi.5
For use as a medicinal ingredient of Traditional Chinese Medicine (TCM) formulations, the fruit is collected in autumn when it turns from pale green to deep green, and subsequently is dried in the open air or at low temperature for several days.6
HISTORY AND CULTURAL SIGNIFICANCE
Previously, S. grosvenorii was previously classified botanically as Momordica grosvenorii and Thladiantha grosvenorii.1 In addition to luo han guo (Standardized Common Name per the American Herbal Products Association’s Herbs of Commerce, 2nd edition)1 and monk fruit, S. grosvenorii is called variously luo han kuo, arhat fruit, big fellow’s fruit,7 rakanka (Japanese), nahan’gwa (Korean),8 momordica fruit,7-9 and longevity fruit.10
In Western terms, dried luo han guo is used in TCM11 for cough,8,9 sore throat and hoarseness,9,12 relieving constipation,9 and dissipating soft nodules in the neck (scrofula).8,13 A tea made from the dried fruit is used for acute or chronic bronchitis, pertussis, pharyngitis, and tonsillitis.7 (The plant’s leaf, luo han ye, has similar properties and also is used for chronic bronchitis and throat conditions.8) In the summer, luo han guo is used as a beverage to relieve thirst and reduce body heat.7
In addition to its use as a beverage in its own right, luo han guo is utilized as a low-calorie sweetening agent in other beverages.7,10 It is estimated that the various mogrosides in fresh luo han guo fruits are anywhere from 200-563 times as sweet as sucrose (table sugar).14,15 In 1986, one reputable source noted that the luo han guo being sold in Taiwanese pharmacies at the time was actually the fruit of Garcinia mangostana or mangosteen (family Clusiaceae)13 — a substitution that was made necessary due to trade restrictions of goods between the People’s Republic of China (PRC) and Taiwan at that time. The dried fruit is also used as an ingredient in some Cantonese soups.10
USES IN COSMETICS, FOODS, AND MEDICINES
In the PRC and other Asian countries where TCM is recognized and practiced — such as Malaysia, Taiwan and Singapore, as well as in some Western countries where TCM is practiced to some extent and its herbal preparations are dispensed in bulk or in finished product form — luo han guo is an active substance indicated for treating dry cough, sore throat and hoarseness of voice due to “heat in the lung,”* as well as being used in formulations for treating constipation due to lack of fluid in the intestine.16
Presently in the United States, most states and the District of Columbia permit the practice of Acupuncture and Oriental Medicine (AOM) with certain varying limitations on the scope of practice. In the states where TCM formulations can be dispensed to patients of licensed acupuncturists (LAc), luo han guo (dried fruit or extract) may be found as a component of herbal mixtures for patient home preparation by traditional decoction method, or of Chinese patent medicines, professional products, or practitioner’s formulations dispensed by compounding pharmacies. Luo han guo may also be found as a component of dietary supplement products freely available outside of clinical practice in the health and natural products channels.
Regarding food use in the United States, in response to a GRAS (Generally Recognized as Safe) notification submitted in 2010 by BioVittoria Ltd. (Hamilton, New Zealand) for its “Siraitia grosvenorii Swingle (Luo Han Guo) fruit extract (SGFE)” substance, the US Food and Drug Administration (FDA) stated that the agency had no questions or objections, meaning that it could be considered to be GRAS.17 The intended use of BioVittoria’s SGFE is as a table-top sweetener and as a sweetener and flavor enhancer in foods, excluding meat and poultry products, at levels determined by current good manufacturing practices (cGMP).
Subsequently, in 2011, in response to a GRAS notification submitted by Guilin Layn Natural Ingredients Corp. (Guilin, Guangxi, PRC) for its SGFE substance, the FDA also had no questions or objections.18 The intended use of Guilin Layn’s SGFE is as a sweetener and flavor enhancer in foods, excluding meat and poultry products, at levels determined by cGMP.
A quality standards monograph for the use of “Monk Fruit Extract” (extract of the fresh fruit luo han guo [Siraitia grosvenorii Swingle] that has been concentrated to optimize the concentration of mogroside V) as a non-nutritive sweetener is published by the United States Pharmacopeial Convention in the Food Chemicals Codex.19
In Canada, “Fructus Momordicae” (luo han guo) is classified as a medicinal ingredient and is listed in Table 1 of the Natural Health Product (NHP) Traditional Chinese Medicinal Ingredients monograph.20 At non-therapeutic dosage levels, “Siraitia Grosvenorii Fruit Extract” also is permitted for use as a non-medicinal ingredient of licensed NHPs for purposes including flavor enhancement and as a sweetening agent, or as a skin-conditioning agent of topical NHPs.21 At the time of this writing (July 2014), there were 15 licensed NHPs containing “Siraitia grosvenorii” as a medicinal ingredient including pastilles for sore throats and some cough syrups. Over 100 licensed NHPs presently list “Siraitia grosvenorii Fruit Extract” or “luo han guo” as a non-medicinal ingredient.22 Also for use as a food additive in Canada, in December 2013, a modification was made to the “List of Permitted Sweeteners” to enable the use of luo han guo extract — standardized to contain 0.8% mogroside V — as a sweetener in tabletop sweeteners.23
In the European Union (EU), luo han guo is classified as a novel food because it was not used as a food or food ingredient before May 15, 1997.24 Before it can be placed on the EU market as a food or food ingredient, a safety assessment under the Novel Food Regulation will be required. Reportedly, at the time of this writing, EU regulatory approval is pending upon application by manufacturers.25
There are, however, four luo han guo ingredients authorized for use in cosmetic products by the European Commission Health and Consumers Directorate General.26 The powder obtained from the dried, ground fruit of Siraitia grosvenorii is listed as an abrasive (removes materials from various body surfaces or aids mechanical tooth cleaning or improves gloss), the juice expressed from the fruit is listed as a humectant (holds and retains moisture) and solvent (dissolves other substances), while, inexplicably, the extract of the fruit of (synonym) “Momordica grosvenorii” is listed as an antioxidant substance while the extract of the fruit of “Siraitia grosvenorii” is listed as a skin-conditioning substance.
There are no known registered Traditional Herbal Medicinal Products in the EU market that contain luo han guo.
MODERN RESEARCH
Laboratory studies of S. grosvenorii have identified the presence and actions of a group of triterpene glycosides known as mogrosides, which are numbered I-V with mogroside V being the most abundant and the sweetest.27 Luo han guo stimulated the secretion of insulin in lab tests on mice, suggesting a potential use as a natural sweetener with a low glycemic index.28 Additional chemical compounds have been identified, including amino acids, flavonoids, polysaccharides, and essential oils, some of which display or augment antioxidant, anti-asthmatic, anti-cancer, antitussive, hepatoprotective, glucose-lowering, and immunoregulating actions in vitro.15 Mogrosides, however, are thought to be the primary active components responsible for the sweetness and main biological effects.15
Animal studies on luo han guo preparations have shown anti-fatigue effects (rabbits);29 cholesterol-, triglyceride-, and glucose-lowering effects;15 antibacterial, anti-cancer, anti-inflammatory, cough-reducing, phlegm-releasing, immunomodulating, antioxidant, and hepatoprotective effects; and physiological function improvement in various animal experiments.15 One rodent study showed that a total mogroside extract as well as a mogroside V and VI extract prevented increases in body, abdominal, and epididymal fat weights, as well as triacylglycerol and total cholesterol levels.30
Unfortunately, there are few human clinical studies on the effects of luo han guo, and all are in non-English language journals (mainly Mandarin). One showed that oral intake of 200 mg/kg of 30% mogrosides did not affect blood sugar or liver enzymes in healthy adults.31 Clearly, as demonstrated by in vitro and in vivo studies, randomized, placebo-controlled, double-blind studies on luo han guo are warranted.
FUTURE OUTLOOK
The main production areas and trading centers for luo han guo, whether wild collected or cultivated, are situated in the southern Chinese province of Guangxi, which borders Vietnam.32 The dried fruit used in TCM formulations or as starting material for the manufacture of extracts is relatively inexpensive at this time. Average market prices in Guangxi over the past year were the lowest during the 2013 harvest, from late August to early October, at only 0.85 yuan/kg (approximately $0.14/kg), reaching a high of 1.49 yuan/kg. Summer 2014 prices were stable at about 1.00 yuan/kg.
While the market for luo han guo appears stable enough to satisfy the current global demand for TCM formulas and products, new demand appears to be due to acceptance in some countries, including the United States and Canada, of standardized extracts of the fresh fruit intended for uses such as food flavor enhancement and/or sweetening.33 The Chinese e-commerce platform alibaba.com lists thousands of luo han guo items offered by hundreds of suppliers, most of which are located in China.
There are now a range of branded ingredients such as those marketed by the companies that initially submitted GRAS notices to the FDA for their SGFE ingredients, namely, Fruit-Sweetness™ (BioVittoria Ltd.) and Go-Luo™ (Guilin Layn Natural Ingredients Corp.).34 The FDA lists other branded ingredients in its statement on additional information about high-intensity sweeteners permitted for use in food in the United States. Specifically, the FDA list contains luo han guo fruit extracts with 25%, 45%, or 55% mogroside V content such as the consumer products Nectresse® (McNeil Nutritionals, LLC; Fort Washington, Pennsylvania), Monk Fruit in the Raw® (In The Raw; Cumberland Packaging Corp.; Brooklyn, New York), and PureLo® (BioVittoria Ltd.).
Since 2003, Guilin Layn has applied for at least ten patents for inventions including “Method to extract Mogrosides from Luo Han Guo” (approved October 20, 2004), “Preparation method to make Luo Han Guo juice” (approved March 14, 2007), “Decolorized Luo Han Guo juice and its producing method” (status not known), and “Method to dry Luo Han Guo with microwave and finished Luo Han” (approved July 20, 2011), among others.35
According to a recent report on sweetener formulations prepared by Rachel Cheatham, PhD (Foodscape Group, LLC; Chicago, Illinois), food and beverage companies remain under significant pressure to reduce the sugar content in their products.14 The trend is for product formulators to steer away from high-fructose corn syrup (HFCS), sucrose, and/or sucralose towards combinations of non-nutritive sweetener blends including, but not limited to, erythritol (produced through fermentation of glucose by fungi such as Moniliella pollinis, Yarrowia lipolytica, and Trichosporonoides megachiliensis), steviol glycosides purified from the leaves of Stevia rebaudiana (Asteraceae), and SGFE.
Replacing sugar in food and drink products is also the subject of a recent industry position paper put out by the UK membership organization Campden BRI wherein monk fruit extract is featured, and, in particular, the branded ingredient Purefruit™ (Tate & Lyle PLC; London, UK) is discussed.25
If the trend to replace HFCS and/or sucrose from food and beverage products continues, and if the new range of commercially available SGFE ingredients perform well as a suitable replacement sweetener substance, the future demand for luo han guo (fruit and extracts thereof) presumably will increase. Cultivation areas will expand in order to fulfill the requirements for the manufacture of purified and standardized extract ingredients. It appears that this new demand from the food and beverage sector may surpass the demand requirements needed for use in TCM formulations and finished herbal medicinal products.
—Gayle Engels and Josef Brinckmann
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