Siraitia grosvenorii

Siraitia grosvenorii is an herbaceous perennial vine native to southern People's Republic of China and Northern Thailand and best known for its fruit, the luo han guo (traditional Chinese: 羅漢果/simplified or monk's fruit). It is one of four species in the genus Siraitia. Botanical synonyms include Momordica grosvenorii and Thladiantha grosvenorii. The fruit is one of several that have been called longevity fruit.

The other species of the genus Siraitia are: S. siamensis from Thailand, S. sikkimensis and S. silomaradjae from India, and S. taiwaniana from the Republic of China (Taiwan).

The vine grows to 3 to 5 m long, climbing over other plants by means of tendrils which twine round anything they touch. The narrow, heart-shaped leaves are 10–20 cm long. The fruit is globose, 5–7 cm in diameter, and contains a sweet, fleshy, edible pulp and numerous seeds.

The fruit extract is nearly 300 times sweeter than sugar and has been used as a natural sweetener in China for nearly a millennium due to its flavor and lack of food energy, only 2.3 kcal/g (9.6 kJ/g). It has also been used in traditional Chinese medicine.

Cultivation
It is grown primarily in the southwestern Chinese province of Guangxi (mostly in the mountains of Guilin), as well as in Guangdong, Guizhou, Hunan, and Jiangxi. These mountains lend the plants shadows and often are surrounded by mists; because of this the plants are protected from the worst of the sun. Nonetheless, the climate in this southern province is warm. The plant is rarely found in the wild and has hence been cultivated for hundreds of years.

Records as early as 1813 mention the cultivation of this plant in the Guangxi province. At present, the Guilin mountains harbor a plantation of 16 square kilometers with a yearly output of about 10,000 fruits. Most of the plantations are located in Yongfu County and Lingui County, which in China are renowned for the extraordinary number of centenarians. This is usually attributed to the consumption of this fruit and the unspoiled nature. The inhabitants themselves, however, are of the opinion that the reason lies in their calm lifestyle and simple nutrition.

Longjiang town ("Dragon River") 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 Uses
The plant is most prized for its sweet fruits, which are used for medicinal purposes, and as a sweetener. Luohan guo fruits are generally sold in dried form, and traditionally used in herbal tea or soup. They are used for respiratory ailments, sore throats and reputed to aid longevity.

The best way to describe the medicinal use of luohan guo in southern China during the 20th century can be found in the book written by Dai and Liu. It was written in Chinese in 1982 and translated into English in 1986. Here is their description:


 * The dried fruit may be bought in a market. The surface of the fruit is round and smooth, it has a yellow-brownish or green-brownish colour, and is covered by fine hairs. The fruit has a hard but thin shell. Inside, one finds a partially dried, soft substance which contains the juice and a large quantity of seeds. All components are very sweet. Their nature is cool and not toxic. The fruit can act as a remedy for sun stroke, wet the lungs, remove phlegm, stop cough and aid defecation.


 * Heat stroke and thirst: Take a fruit, break it open and pour hot water on it to make an infusion. Drink the infusion in place of tea.
 * Acute or chronic infection of the larynx (aphonia): Take the halves of a fruit and 3 to 5 sterculia seeds, cover this with water and leave it to boil. Swallow very slowly.
 * Chronic cough: Take a piece of the fruit, cover it with water and leave it to boil. Drink the resulting liquid twice daily.
 * Constipation due to old age: Take two fruits and, using only the soft parts and seeds, divide it into pieces. Cover these pieces with water, boil it, and drink the liquid before going to bed.
 * Diabetes: Take an appropriate amount of fruit squash or boil it so as to get concentrated juice. Use this as a substitute for sugar in your nutrition..

Active agents
The sweet taste of luohan guo comes mainly from the mogrosides, a group of Triterpene-Glycosides that make up approximately 1% of the flesh of the fresh fruit. Through extraction, a powder containing 80% mogrosides can be obtained.

Five different mogrosides are known and they are known by names with the numbers 1 to 5. The main mogroside in this plant is mogroside-5, that was previously known as esgoside.



Other similar agents in luohan guo are Siamenoside and Neogroside.

The pure mogroside mix present results in a sweetness that is 300 times sweeter than sugar. The 80% mix is approximately 250 times sweeter. Pure mogroside-5 and -5 can be up to 400 times as sweet.

Toxicity
There are no reported incidents of negative side effects of luohan guo that are known. It is classed by the American Food and Drug Administration as a GRAS (generally recognized as safe) product. There are no restrictions on consuming the fruit or its extracts.

Current research
Recent research on luohan guo suggests that the mogroside works as an antioxidant and that it helps to prevent cancer.

The use of luohan guo as a remedy for diabetes and overweight has been mentioned, as it can be used as a substitute for sugar.

Luohan guo has been shown to be useful against the Epstein-Barr virus.

The plant also contains a glycoprotein called momorgrosvin, which has been shown to inhibit ribosomal protein synthesis

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. Furthermore, it develops a rotten taste on fermentation, which adds to the unwanted flavours already present.

Thus the fruits are usually dried before further use and are sold in precisely this fashion in Chinese herbal shops. The fruits are slowly dried in ovens, which preserves it and removes most of the unwanted aromas. However, this technique also leads to the formation of several bitter and astringent aromas. 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 added to them.

The Procter & Gamble process
The process for the manufacture of a useful sweetener from luohan guo was patented in 1995 by Procter & Gamble. The patent states that, while luohan guo is very sweet, it has too many interfering aromas, which render it useless for general application. Thus the company developed a process for the removal of the interfering aromas.

In this process, the fresh fruit is harvested before it is fully mature, and is then matured in storage so that it may be processed precisely when it is mature. The shell and seeds are then removed, and the pulped fruit is made into a fruit concentrate or puree. This is then used in the further production of food. Solvents are used, amongst other things, to remove the interfering aromas.

Products
There are a number of commercially prepared luohan guo products:

One of the most famous ones is powdered instant luohan guo, which is also sold by the Yongfu company. It is sold in China, Hong Kong and in Chinese shops in the West.

In addition, there are a number of other products which contain luohan guo either on its own or in a mix with other herbs. For example it is used with Ginkgo against cough, with chrysanthemum against heatstroke and headache or with asparagus, Oldenlandia, Scutellaria, and pearl powder to detoxify.

History
During the Tang dynasty, Guilin was one of the most important Buddhist retreats containing many temples. The fruit was named after the arhats, a group of Buddhist monks who, due to their proper way of life and meditation, achieved enlightenment and were said to have been redeemed. According to Chinese history, the fruit was first mentioned in the records of the 13th century monks who used it.

However, plantation space was limited: it consisted mainly in the slopes of the Guangxi and Guangdong mountains, and to a lesser degree in Guizhou, Hunan, Jiangxi, and Hainan. This and the difficulty of cultivation meant that the fruit did not become part of the Chinese herbal tradition, which depended on more readily available products. This is also the reason why one finds no mention of it in the traditional guides to herbs.

Rediscovery in the 20th century
The herb became better known in the 20th century. The first report on the herb in English was found in an unpublished manuscript written in 1938 by Professor G. W. Groff and Hoh Hin Cheung. The report stated that the fruits were often used as the main ingredients of "cooling drinks," that is, as remedies for hot weather, fever, or other dysfunctions traditionally associated with warmth or heat.

It was known that the juice of the fruits was very sweet.

Groff and Hoh realised that the fruit was an important Chinese domestic remedy for the treatment of cold and pneumonia when consumed with pork.

Interviews have confirmed that the fruit only recently gained importance in Chinese history. Nonetheless, it appears that a small group of people had mastered its cultivation a long time ago and had accumulated extensive knowledge on growth, pollination, and climatic requirements of the plant.

The fruit came to the United States in the early 20th century. Groff mentions that during a visit to the American ministry of agriculture in 1917, the botanic Frederick Coville showed him a luohanguo fruit bought in a Chinese shop in Washington. Seeds of the fruit which had been bought in Chinese shop in San Francisco were entered into the universal botanic description of the species in 1941.

The first research into the sweet component of luohanguo 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).

The development of luohanguo products in China has continued ever since, focusing in particular on the development of concentrated extracts.