1.1 What is a longan?
The longan (botanical name: Dimocarpus longan, also known as dragon’s eye; Chinese Pinyin: Long Yan, Simplified Chinese: 龙眼), is a species of tropical, flowering, fruit-bearing tree in genus Dimocarpus in the soapberry family, Sapindaceae. The flowers are brownish-yellow, small in size (about 2.5 mm long), with 5 to 6 petals. The edible fruit is nearly spherical, small in size between 1-2.5 cm in diameter with yellow, bark-like skin. The plant can grow up to 30 m tall. Native to Southern Asia and extensively cultivated in southern China (including Taiwan Province), northern Thailand, Cambodia, Laos, Vietnam, India, Sri Lanka, Philippines, Australia, U.S., and Mauritius, habitats of longan include open forest, mountainous regions, orchards, roadsides and village margins (usually found from between 0 to 500 meters in elevation). Characteristics of longan include tolerance for drought and adaptation to barren land.
Other simplified Chinese names for longan include: 桂圆, 三尺农味, 益智, 亚荔枝, 十叶, 石圆, 脆肉, 龙目, 圆眼, 荔枝奴, 骊珠, 燕卵, 蜜脾, 鲛泪, 川弹子.
1.2 What does a longan fruit taste like?
Good longan fruits have a crisp, juicy, meaty, firmed texture with a flavor that is sweet and musky.
1.3 How do I tell if my longan fruits are ripe?
Longan fruits ripen when the fruit skin turn smooth with an intense tan color. Sampling is suggested as the main ripeness indicator is pulp sweetness. As longan fruits are non-climateric, they need to be harvested when ripe, or else cracking and spoiling may occur. Most ripe longan fruits are found in middle of July, August and to early September, depending on the weather conditions.
1.4 How long does it take for a longan tree to grow?
After field planting, it may take 4~5 years for a longan seedling tree to start to bear fruits. Air layering (a method of propagating new trees and shrubs from stems still attached to the parent plant) may taken 2~3 years. Note that longan trees bear fruits erratically, in another word there may be some years the longan trees do not produce flowers and fruits.
1.5 How is longan fruit used in traditional Chinese medicine?
The the flesh of dried longans is considered to have sweet and warm properties and to be associated with the heart and spleen meridians. It is used as digestion aid, blood enricher, spleen tonic, heart tonic, sedative, brain-strengthening drug and nootropic drug in traditional Chinese medicine (CTM) and widely adopted in treating different diseases and health problems, such as loss of appetite and heart palpitation.
2. Uses, Health Benefits of Longan Fruits & Medical Formulas
2.1 Ensure Bowel And Intestine Health
Longans fruits are rich in dietary fiber which is also known as roughage or bulk, it is actually parts of plant foods our body can’t absorb in our digestive tract. Dietary fiber include two types: soluble and insoluble. In particular the insoluble fiber promotes the movement of material through our digestive tract and increases stool bulk, therefore it help treat gastrointestinal disorder and chronic constipation (a syndrome which can be defined as unsatisfactory defecation that results from difficult stool passage or infrequent stools, hard stools, or feeling of incomplete defecation).
2.2 Protect Brain And Nervous System
Longans fruits also contain rich Vitamin C which is also known as ascorbic acid. According to United States Department of Agriculture (USDA), longan fruits contain 84 mg Vitamin C (equivalent to 101% RDA) per 100 g (3.5 oz) serving. Despite the fact that Vitamin C may not be absolutely required for any specific action in a cell, studies suggest that Vitamin C is definitely necessary for proper function of many organs, in particular the brain and central nervous system (CNS) (James 2013).
2.3 Tighten Up Loose Skin
Everyone of us may develop sagging skin with age as our skin loses its natural elasticity, it is part of the aging process. In another situation, a large weight loss can also lead to loose, extra skin. It is important to tighten up loose skin because no one want to look decades older than his or her actual age. Saggy skin develops when our skin stops producing enough of collagen and elastin fibers, studies show that Vitamin C can boost collagen production, which in return restores elasticity to the skin. Therefore, Vitamin C rich food such as longans fruits can serve as an excellent home remedies for saggy skin.
2.4 Boost Immune System And Metabolism
Longans fruits also contain a high level of Vitamin B2, which is also known as riboflavin. Vitamin B2 is an important vitamin that serves as an antioxidant within the body. Vitamin B2 is also vital for the formation of FAD (flavin adenine dinucleotide) and FMN (flavin mononucleotide), both of which are essential for metabolising carbohydrates, proteins, and fats and make energy available in the body. Getting too little riboflavin may lead to weakness, throat swelling/soreness, a swollen tongue, cervical cancer, and migraine headaches.
2.5 Spleen Tonic
[CTM Formula] Medicated soup with flesh of dried longans (also known as dried longan meat), seed of wild jujube, Astragalus propinquus, white atractylodes rhizome, poria with hostwood, costus root, licorice root (Glycyrrhiza glabra), ginger and jujubes is taken orally to tonify and invigorate the spleen.
2.6 Enrich Blood
[CTM Formula] A decoction of dried longans and refined white sugar is taken orally to enrich blood.
3. Contraindication, Side-effects & Cautions
Administration with caution for people experiencing cough.
The Ben Cao Medical Book (also known as Compendium of Materia Medica or Ben Cao Gang Mu; Chinese: 本草纲目) is the most famous and comprehensive medical book ever written in the history of traditional Chinese medicine (TCM). Compiled and written by Li Shi-zhen (1518~1593), a medical expert of the Ming Dynasty (1368-1644) over 27 years.
The Ben Cao Medical Book records and describes all the plants, animals, minerals, and other objects that were believed to have medicinal properties in TCM. The book reflects the pharmaceutical achievements and developments of East Asia before the 16th century. On the basis of his predecessors’ achievements in the pharmacological studies, Li contributed further by supplementing and rectifying many past mistakes and misconception in relate to nature of many medicinal substances and causes of various illnesses. Charles Darwin, originator of the biological theory of evolution, regards the book as the “ancient Chinese encyclopedia”.
Disclaimer: The Ben Cao Medical Book is translated by ChinaAbout.net. The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. It is intended as a sharing of CTM knowledge and information from the research and experience from the author Li Shi-zhen. Kindly be alert that the CTM knowledge and ancient formulas given above are likely NOT medically proven and may contain misconceptions.
List of reference
James, M. M. 2013 Vitamin C transport and its role in the central nervous system, Subcell Biochem. 2012; 56: 85–103.