Medicinal Properties of Longan Fruit
Longan fruit has been used in Traditional Chinese Medicine for thousands of years as a remedy for many diseases, ranging from insomnia to snake bites. Longan contains unique active compounds and antioxidants, which may enhance cognition, support brain and heart health, and boost the immune system. Read on to learn about all the health benefits and potential side effects of longan.
What is Longan Fruit?
Longan (Dimocarpus Longan) is a fruit grown in China, India, Sri Lanka, and many other Asian countries. It belongs to the same family (soapberry) as fruits like lychee [R].
The longan fruit is used as in Traditional Chinese Medicine (TCM) as a sleep aid, relaxant, to improve digestion, alleviate nerve pain, reduce fever, clean parasites, and even as an antidote to snake poison [R, R].
The fruit looks like an eyeball when peeled, which earned it the name “dragon’s eye” in Chinese.
Both the flowers and seeds of Longan are used as remedies. Longan flowers are sold in herb markets, have a fruity aroma, and are used to prepare an infusion in Taiwan. The powder of dried longan seeds is traditionally used to reduce bleeding, relieve swollen lymph glands, and soothe eczema [R].
Longan fruit is succulent and has gained popularity as an exotic refreshment. Thanks to this popularity, longan fruit is now produced in large quantities in China. Wine from the longan fruit is also considered a “functional food” in TCM, used for various ailments [R, R, R].
Active Compounds & Mechanisms
Longan flowers, seeds, pulp, and the whole fruit contain a unique combination of bioactive compounds.
The longan flowers and seeds are rich in polyphenols, strong antioxidants. They contain proanthocyanidins, which are also the main active compounds in grape seed extract and may protect from heart disease and cancer [R].
Longan fruit, pulp, and extracts contain:
- Antioxidants, such as ellagic acid, quercetin, and kaempferol [R, R]
- Polysaccharides, which may boost immunity and fight many chronic diseases [R, R]
- Adenosine, which enhances sleep and relaxation. Adenosine is also produced naturally in the body and boosts restorative deep sleep (opposite to caffeine) [R, R].
- Uridine, which may boost cognition and mood [R]
- Chlorogenic acid, which boosts weight loss and protects the heart [R]
- GABA, the main calming and relaxing neurotransmitter [R]
- Vitamin C [R]
- Corilagin, which may reduce blood pressure [R]
The pulp contains more active compounds than the fruit, but these can vary depending on the manufacturer and longan variety [R].
Longan leaf extract, although less researched and used, is also rich in unusual anti-inflammatory sugar-bound flavonoids. Two of these compounds were completely unknown to science until recently [R, R].
Health Benefits of Longan
1) Longan May Protect the Brain
Longan flowers prevented Parkinson’s disease in rats by protecting the dopamine neurons in the brain from damage. It could also boost antioxidants and reduce inflammation in brain cells [R].
Polysaccharides from longan reduced brain damage in rats with stroke and increased antioxidant enzymes such as glutathione and SOD in the brain. They also increased the activity of genes that protect brain cells (Bcl-2) [R].
A Traditional Chinese Medicine herbal mix containing longan prevented brain damage in mice with Alzheimer’s disease. Interestingly, this herbal mix could activate an antioxidant protein (HO-1) in the brain’s memory hub, the hippocampus [R, R].
2) Longan May Boost the Immune System
Longan pulp increased the activity of white blood cells in several cell studies. The polysaccharides in longan are its strongest immune-boosting compounds. This immune-enhancing effect was stronger in a less acidic environment in cells [R, R, R].
In one cell study, longan polysaccharides increased in the number of spleen immune cells (splenocytes), made immune cells ingest and degrade harmful foreign materials, and activated natural killer cells to kill lymphoma [R].
Longan pulp polysaccharides increased antibody production in mice with suppressed immune systems [R].
3) Longan May Be An Antioxidant
Longan is rich in gallic acid and ellagic acid, which are excellent antioxidants. The fruit’s extract neutralized free radicals and reduced inflammation in immune cells [R].
It could reduce inflammation in mice by boosting antioxidant enzymes such as glutathione and SOD [R].
Longan seeds extracts contain more ellagic acid than mango kernel extracts [R].
4) Longan May Reduce Inflammation
The antioxidants in longan not only boost antioxidant enzymes but also affect important inflammatory pathways.
In one cell study, the flower extract could reduce nitric oxide and inflammation better than the seed and pulp. It could also block inflammatory pathways that increase cytokines on a DNA level (NF-kB and AP-1, MAPK) [R].
5) Longan May Combat Cancer
Longan contains compounds that could prevent or fight cancers, based on studies in cells and animals. Longan’s cancer-fighting potential comes from its phenolic compounds, flavonoids, and polysaccharides found in the flowers, fruit, or seed [R, R, R].
In several cellular studies, longan seed extracts could fight lymphoma, colon, liver, breast, uterine, and lung cancers. Of these, longan had the strongest effect on breast cancer cells, killing more than 60% of them and stopping their growth [R].
On a DNA level, longan could reduce the activity of genes that help cancer cells divide and spread. It can silence cancer-causing genes, also known as “oncogenes”, and turn on cancer-fighting genes, “antioncogenes” in cells [R].
One of the bad genes it could silence is especially important (cyclin D1), as it plays a role in every aspect of cancer, from its initial growth and spreading to drug resistance and metastasis [R].
Longan seed extract could block matrix metalloproteinases (MMPs) in test tubes and in colon cancer cells. Since MMPs help cancers invade tissues and cause metastases, longan could potentially prevent this process [R, R, R].
Longan flower extract could trigger autodestructive mechanisms in cancer cells, causing cancer cells to degrade themselves. It did so by activating caspases and affecting the mitochondria (by increasing Bcl-2). In fact, cells in which this natural autodestruction (apoptosis) doesn’t work as well are found not only in cancer but also in autoimmune and brain diseases [R].
High-quality longan fruit extracts may be more potent than their isolated ingredients. Fruit extracts could kill liver, lung, and stomach cancers in cells while increasing antioxidants. An isolated polysaccharide from the longan fruit (an alpha D-glucan) only reduced the growth of liver cancer cells and had no effect on breast cancer cells. [R, R, R].
When this compound was chemically modified, it could fight a type of head and neck cancer in cells [R].
6) Longan May Help with Insomnia
Dried seeds of the longan fruit have long been used as a traditional remedy for insomnia. The indication in TCM for longan is to “revitalize the heart & spleen, nourish blood & calm the mind”. And all though it’s still commonly used as a sleep aid, no clinical studies can attest to this effect R].
Animal studies do point to sleep-enhancing benefits. Longan improved sleep in stressed mice[R].
In mice, longan seed did not directly improve sleep but enhanced the effects of a sleep-inducing sedative (pentobarbital) by boosting GABA activity in the brain [R].
Longan also contains adenosine, which had anxiety-relieving effects in mice. Adenosine is the body’s natural sleep aid, and one that caffeine blocks. The adenosine content in longan may help explain its traditional use for sleep and anxiety [R, R].
7) Longan May Help with Diabetes
Longan flower extract improved insulin resistance in mice fed a high-sugar diet. It could also boost antioxidant defense and prevent high blood pressure. Altogether, these effects could prove to be beneficial for people with metabolic syndrome [R].
8) Longan May Reduce Blood Pressure
A component from longan seeds (corilagin) reduced blood pressure in rats with high blood pressure. Longan could do this by relaxing the blood vessels, reducing the fight-or-flight response and decreasing noradrenaline [R].
9) Longan May Improve Gout
In test tubes, longan leaves could somewhat block the enzyme (XOD) that causes uric acid buildup in gout. Many drugs used to treat gout act similarly. Longan leaves had some effect compared to the typical gout medication (allopurinol), while the fruit did not. But these effects were much weaker compared to papaya, which outdid even the conventional medication [R].
In another study, longan seeds could block this pathway in cells. The seeds also reduced blood uric acid levels in mice with gout [R].
10) Longan May Improve Anemia
In a study (RCT) of 200 pregnant women with anemia, a Traditional Chinese Medicine (TCM) combination, which included longan increased red blood cell count and hemoglobin. As an add-on remedy, it had a stronger effect than just the standard treatment (ferrous fumarate, vitamin C, and folic acid) after 2 weeks [R].
In all three of the above studies, longan was used as part of “dietotherapy”, a TCM approach that involved 6 g dried pulp and 2 eggs per day along with other specific herbs.
11) Longan May Improve Memory
Longan fruit extract improved learning and memory in mice. It increased BDNF in the hippocampus, the most important brain region for memory and the only one where we know new brain cells can be created. This extract could also increase the survival of young brain cells [R].
A mix of 4 herbs including longan improved memory in mice with Alzheimer’s disease. It could also protect the brain from oxidative, which is important for preventing cognitive decline [R].
12) Longan May Help Burn Fat
Longan fruit extract prevented weight gain and a rise in blood lipids in rats fed a high-calorie diet. Its effects wide quite wide-ranging, including all of the following [R]:
- Reduced body weight and overall fat
- Reduced blood triglycerides levels
- Reduced liver fats
- Reduced the activity of genes that make and store fats in the body (FAS)
- Increased the activity of genes that reduce LDL (LDLR)
- Increased PPAR alpha, which boosts metabolism and fat burning
- Enhanced fat elimination through the stool
Longan fruit extracts also contain probiotic bacteria (Pediococcus pentosaceus), a type of lactic acid bacteria. This plant-based probiotic reduced weight gain, overall and liver fats in obese mice fed a high-fat diet[R].
13) Longan May Be Anti-Aging
Longan owes its potential anti-aging effects to its antioxidant compounds, which can neutralize free radicals, and to its glucose-reducing and insulin-sensitizing benefits [R].
Longan could reduce glycation in cells, a process that contributes to aging. Glycation is a process during which important proteins and DNA are changed and their activity altered. People with diabetes, due to high blood sugar, are especially affected by it [R, R, R].
However, no clinical studies have confirmed this. Plus, many factors that drive aging are still unknown. For now, the anti-aging benefits of longan are uncertain.
14) Longan May Boost Energy Levels
The polysaccharides in the seed extract may reduce fatigue and boost energy. In mice, they enhanced endurance, increased energy stores, and reduced lactic acid, which causes muscle fatigue and cramps [R].
15) Longan May Boost Bone Health
Longan may boost bone health, but this effect is still limited to cellular studies. The fruit extract increased the activity bone-building cells [R].
Side Effects and Safety
Some people may be allergic to longan. In one reported case, a man with mango allergies and asthma experienced itching, hives, and swelling after consuming longan [R].
In animal studies, longan didn’t have any adverse effects.
Lychee contains compounds that may dramatically reduce blood sugar in humans. Several medical issues have been associated with lychee, which belongs to the same family as longan. It’s unknown if longan fruit may have the same effects. Consult your doctor before supplementing, especially if on anti-diabetes medication [R, R, R].
Limitations and Caveats
Clinical studies investigating the effects of longan are lacking The majority of studies have been done in mice or cells. Just a couple of studies examined the effects of longan as a herbal combination in Traditional Chinese Medicine.
Various studies focused on different parts of the plant, such as the fruit, pulp, seed, or specific extracts. The fruit varieties, its parts, and extracts differ a lot in active compounds.
Natural Sources and Supplements
Longan fruit is sold fresh in Asian markets, or available as a dried fruit, mostly in Chinese stores.
Longan is also available in tincture, capsules, or powder form [R].
Extracts are made from the flowers, fruit, or seeds. Most supplements are Traditional Chinese Medicine preparations, in which longan is often combined with other herbs. You may see “Long Yan Rou” on some supplements – this is the Chinese name for longan.
Due to the lack of clinical studies, the dosing is not well defined.
A couple of conducted clinical studies used 6 g of the dried pulp/day.
The typical TCM dosage is 6 – 15 g/day of the fruit.