Longan (Dimocarpus longan Lour.): A Comprehensive Reference
1. Identity: Botanical Classification, Names, and Natural Source
Dimocarpus longan Lour. is a subtropical evergreen plant belonging to the family Sapindaceae, widely known as longan. Also known by the Chinese name guiyuan, longan is widely distributed in Southeast Asia and Southern China, especially in Guangdong, Guangxi, and Fujian, and China accounts for approximately 60% of the world's longan production. It is cultivated in several countries in East Asia and Southeast Asia, as well as Australia and some subtropical regions of the United States, with China and Thailand being the largest areas of commercial cultivation.
This tropical and subtropical evergreen tree species is mainly found in China, India, and Thailand, and is also found naturally in Bangladesh. Longan (Dimocarpus longan Lour.) is an arilloid fruit tree belonging to the Sapindaceae family. An older synonym encountered in historical literature is Euphoria longana Lam., which refers to the same species.
The common name "longan" derives from the Cantonese pronunciation of the Chinese lóng yǎn (龙眼), meaning "dragon eye," a reference to the appearance of the peeled fruit — a white, translucent ball encasing a dark seed. In Traditional Chinese Medicine (TCM), the dried flesh is specifically referred to as Long Yan Rou (龙眼肉) or Gui Yuan Rou (桂圆肉).
Parts Used and Common Preparations
Different parts of this plant, especially juice pulp, pericarp, seeds, leaves, and flowers, contain a diverse group of botanical phytocompounds and nutrient components. The pulp of longan is crisp and sweet, suitable for fresh consumption or processing into jam, juice, dried pulp, and wine. Longan can be consumed in both fresh and processed products such as ointment, wine, and canned longan.
Both longan flowers (long yan hua) and fruit (long yan rou) are used in traditional Chinese medicine and herbal preparations, but the fruit is used much more frequently. In supplement form, preparations include dried whole arils, aqueous or ethanolic extracts of the pulp, pericarp, seed, or flower, and polysaccharide-enriched fractions. The dried pulp (arillus) is the most classically recognized medicinal form.
2. Traditional and Historical Use
China: The Primary Tradition
Long Yan Rou has been used medicinally in China since at least the Han Dynasty (around 200 BCE). According to historical records, the Han emperor attempted to transplant longan and lychee trees to his palace gardens in Shaanxi, but they failed to survive the cooler climate. Longan cultivation later flourished in the warmer provinces of Fujian and Guangdong, becoming a major industry.
Longan is considered a valuable tonic and has been traditionally used as a medicinal plant. In ancient China, longan was a highly coveted tribute item in royal courts. In the Ming Dynasty, the renowned traditional Chinese medicine expert Li Shizhen referred to longan as the "king of fruits" in his seminal work, Ben Cao Gang Mu.
In TCM, Longan (龙眼, lóng yǎn), known as Gui Yuan Rou (桂圆肉), refers to the dried flesh of the longan fruit. Native to Southern China and a relative of the lychee, this fruit has been used for centuries to support emotional balance, replenish energy, and nourish the body from within. It is considered sweet and warm in nature, and primarily enters the Heart and Spleen meridians.
In ancient TCM texts, longan — known as Gui Yuan in Chinese — was recorded as a fruit with properties that nourish the heart and spleen, boost vitality, relieve fatigue, and calm the mind. In traditional Chinese medicine, longan has long been used to reduce acute reactions and detoxify the body, to improve blood metabolism, to preserve neuronal cells, and to treat pain, urinary diseases, fatigue, and insomnia.
Classic TCM Formulas
In TCM, longan has earned a prominent place in classic formulas. One notable example is Guipi Soup (归脾汤), a famous remedy used to treat symptoms of heart and spleen deficiency, such as insomnia, forgetfulness, heart palpitations, and fatigue. Longan fruit, known as longan meat when dried, forms a key ingredient in this soothing herbal mix.
Postpartum and Tonic Uses
The Chinese have long enjoyed dried longan, boiling it into a warm, restorative drink or adding it to soups believed to nourish the blood and ease exhaustion. After childbirth, Chinese women are traditionally given longan tea blended with herbs to help rejuvenate the body, as longan is thought to restore strength and enrich the blood. Because of its heating qualities in TCM, it is brewed into tonic teas for women who have just given birth and fed to the elderly. Dried longan is prescribed by TCM practitioners for those who are anaemic.
Bangladesh and South/Southeast Asian Traditions
In Bangladesh, the plant is locally used as "kaviraj" medication for treating different diseases such as gastrointestinal disorders, wounds, fever, snake bites, menstrual problems, chickenpox, bone fractures, neurological disorders, and reproductive health. Various parts of longan, including seeds, pericarp, and pulp, have long been used in traditional medicine in China, Thailand, and other Asian countries.
Seeds and Pericarp in Traditional Practice
D. longan seed has been administered to counteract heavy sweating, whereas the ground kernel has been used for the treatment of various conditions according to its chemical components such as saponin, tannin, and fat. In China, longan is considered a "Medical Food Homology" and has been used in traditional Chinese medicine to cure insomnia and neural pain and to stop sweating and bleeding.
3. Key Constituents and Active Compounds
Overview of Phytochemical Classes
Longan fruit has high nutritional and medicinal values, and its main functional metabolites include polysaccharides, flavonoids, alkaloids, and carotenoids. It contains numerous nutrients, including phenolic acids, flavonoids, glucose, amino acids, and vitamins. Longan fruits are rich in carbohydrates, fiber, vitamin C, and amino acids.
Polyphenols and Phenolic Acids
Four polyphenolic substances — gallic acid, ethyl gallate, corilagin, and ellagic acid — have been identified and quantified in longan byproducts using HPLC. Among these, corilagin was the major polyphenolic component in both pericarp and seed.
The pulp is the chief source of major phytocompounds including protocatechuic acid, vanillic acid, caffeic acid, 4-methylcatechol, p-coumaric acid, ferulic acid, syringic acid, chlorogenic acid, quinic acid, narirutin, naringin, rhoifolin, hesperidin, gallic acid, epicatechin, (-)-epicatechin, isoquercitrin, and coumarin.
The most important chemical constituents of the pericarp of longan include friedelin, friedelanol, (24R)-stigmast-4-en-3-one, β-sitosterol, 6-hydroxy-7-methoxycoumarin, β-daucosterol, corilagin, gallic acid, heptyl p-hydroxybenzoate, methyl gallate, 4-O-α-L-rhamnopyranosyl-ellagic acid, and ellagic acid. The most notable antioxidant compounds extracted from longan shells are scopoletin, isovanillin, astragalin, quercetin, β-phenylethyl alcohol, and hyperin.
Analyses of polyphenolic distribution showed a large variation in the contents of gallic acid, corilagin, and ellagic acid in different plant tissues and cultivars. The seed contained the highest levels of these three phenolics, while the pulp contained the lowest.
Flavonoids
From extracts of Dimocarpus longan Lour. leaves, 2 unusual flavonol glycosides — quercetin 3-O-(3″-O-2‴-methyl-2‴-hydroxylethyl)-β-D-xyloside and quercetin 3-O-(3″-O-2‴-methyl-2‴-hydroxylethyl)-α-L-rhamnopyranoside — as well as 10 known compounds including flavonol glycosides (afzelin and kaempferol-3-O-α-L-rhamnopyranoside), flavans ((-)-epicatechin and proanthocyanidin A-2), triterpenoids (friedelin, epifriedelanol, and β-amyrin), and sterols (β-sitosterol and daucosterol) were isolated and identified.
After silica gel column chromatography, the fraction of longan flower extract with superior antioxidant activity was identified as containing two major compounds: (-)-epicatechin and proanthocyanidin A2.
Polysaccharides
Pharmacological studies of longan polysaccharides (LPs) have shown a variety of biological activities: LPs can enhance free radical scavenging ability, immunomodulation, anti-tumor effects, and also regulate the dynamic balance of intestinal flora and enhance memory.
The soluble longan polysaccharides (LP) were found to contain arabinose, mannose, glucose, and galactose, with the main linkages of the saccharide residues being (1→4)-β-glucose and (1→6)-β-mannose. The carbohydrate portions of polysaccharide-protein complexes from longan pulp (LP1–3) were principally composed of glucose, arabinose, and mannose.
Seed-Specific Compounds
p-Coumaric acid-glycoside, (S)-flavogallonic acid, ellagic acid derivative, and methyl-ellagic acid glucopyranoside were first identified in longan seeds. Ellagic acid and its derivative and p-coumaric acid-glycoside had important contributions to the potent antioxidant activity of longan seed extract.
Dried longan seed is a source of polyphenol-rich antioxidant compounds such as corilagin, gallic acid, and ellagic acid.
Alkaloids
The alkaloid extract of longan seed showed the highest DPPH radical scavenging activity and oxygen radical absorbance capacity among tested fractions. Flavonoids in seed and alkaloids in pericarp showed potential to be developed as anti-hyperglycemic agents.
4. Mechanisms of Action
Antioxidant Mechanisms
Longan flower extracts were assayed using DPPH free radical scavenging, oxygen radical absorbance capacity (ORAC), and inhibition of Cu²⁺-induced oxidation of human LDL methods, demonstrating significant antioxidant capacity. Water extract of longan pericarp (WLP) exhibited radical scavenging, reducing activity, and liposome protection activity. WLP also inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production in macrophages.
Anti-inflammatory Mechanisms
Administration of WLP in the range of 100–400 mg/kg showed a concentration-dependent inhibition on paw edema development in a carrageenan-treatment model in mice. The anti-inflammatory effects of WLP may be related to NO and tumor necrosis factor (TNF-α) suppression and associated with increases in the activities of antioxidant enzymes, including catalase, superoxide dismutase, and glutathione peroxidase.
Mechanistic studies using an in vitro Caco-2/RAW264.7 coculture system revealed that purified longan polysaccharide fractions effectively suppressed NF-κB pathway activation through downregulation of TLR4 expression, reduction of the p-IκB-α/IκB-α ratio, and inhibition of nuclear NF-κB translocation. These molecular effects correlated with decreased production of inflammatory mediators (TNF-α, IL-6, IL-8, iNOS, and NO).
Immunomodulatory Mechanisms
Longan polysaccharides have shown bioactivities including antioxidative, antitumor, and immunoregulatory activities, as well as regulation of intestinal flora and intestinal metabolites. A novel polysaccharide isolated from longan (LP4) was found to activate macrophages via TLR2/4-mediated signaling pathways.
Neuroprotective Mechanisms
An in vitro study showed that longan flower water extract (LFWE) concentration-dependently inhibited lipid peroxidation of brain homogenates. The antioxidative activity of LFWE was more potent than that of glutathione or Trolox.
Anticancer Mechanisms
Apoptosis is the essential mechanism by which unwanted or damaged cells are eliminated during development or maintenance of tissue homeostasis. Defective regulation of apoptosis has been closely associated with chronic diseases including cancer. Inducing cancer cells into apoptosis is the main mechanism by which anti-neoplasm drugs or natural products suppress cancer cell growth. Longan extracts appear to operate through this pathway, as well as through cell-cycle arrest.
5. Scientific Evidence by Area of Use
5.1 Antioxidant Activity
The aril of D. longan contains several polyphenols, flavonoids, organic acids, and polysaccharides, and possesses various beneficial biological activities including antioxidant, antiglycation, anticancer, immunomodulatory, prebiotic, anti-osteoporotic, anxiolytic, and memory-enhancing effects.
Longan seed extract was identified as the most potent anti-hyaluronidase and antioxidant among tested fractions, with the strongest free radical scavenging and reduction power, while black D. longan aril extract resulted in the highest inhibition of inflammatory cytokine secretion. Black D. longan contained more biologically active compounds and possessed more potent biological activities than conventional dried D. longan.
Evidence strength: The antioxidant effects of longan and its various parts are well-documented across multiple in vitro studies and some animal studies. No human clinical trials specifically measuring antioxidant endpoints in longan-supplemented participants have been identified in the published literature. The evidence base is predominantly preclinical.
5.2 Immunomodulatory Activity
The immunomodulatory function of longan pulp polysaccharide-protein complex (LP3) was investigated in immunosuppressed mouse models. Compared with the model control, peroral administration of 100 mg/kg/day LP3 could significantly increase antibody production against chicken red blood cell (CRBC), concanavalin A-induced splenocyte proliferation, macrophage phagocytosis, NK cell cytotoxicity against YAC-1 lymphoma cell, and interferon-gamma (IFN-γ) and interleukin-2 (IL-2) secretion in serum.
Immunomodulatory effects were also observed in mice administered with 50 or 200 mg/kg/day LP3. The beneficial effects of 50–200 mg/kg/day LP3 were comparable to those of 50 mg/kg/day ganoderan (a reference immunomodulating polysaccharide from Ganoderma).
For a certain dose, all three polysaccharide-protein complex fractions (LP1–3) could significantly stimulate splenocyte proliferation, macrophage phagocytosis against neutral red, and NK cell cytotoxicity against YAC-1 lymphoma cell. The results demonstrated that the polysaccharide-protein complexes of longan pulp have medical potential as immunotherapeutic adjuvants.
Evidence from mechanistic studies provides compelling support that longan polysaccharides possess dual immunomodulatory and antioxidant capabilities, highlighting their potential as natural adjuvants for alleviating chemotherapy-induced side effects.
Evidence strength: Immunomodulatory effects have been consistently demonstrated in cell-based and animal studies. Human clinical evidence is absent. All conclusions regarding therapeutic application in humans remain preliminary.
5.3 Neuroprotection and Cognitive Function
Traditional medicine has used longan fruit pulp to treat insomnia, promote mental calmness, relieve neurasthenia, and prevent cognitive decline.
An ex vivo study found that basal lipid peroxidation and heat-induced lipid peroxidation were lower in brain homogenates of longan flower water extract (LFWE)-treated rats (500 mg/day), indicating that the brains of LFWE-treated rats were more resistant to oxidative stress. An animal Parkinsonian model demonstrated that oral administration of LFWE (125–500 mg/kg/day) dose-dependently attenuated 1-methyl-4-phenylpyridinium (MPP⁺)-induced neurotoxicity in the nigrostriatal dopaminergic system of rat brain.
Polysaccharides extracted from longan fruit pulp were shown to result in better learning and memory in mice by passive avoidance tests.
Evidence strength: Neuroprotective effects are supported by in vitro and animal model studies only. The Parkinson's model study used a rodent model, not human subjects. There are no registered or completed human clinical trials on longan for neuroprotection or cognitive decline reported in the indexed literature.
5.4 Anticancer Activity
Longan flower extract (LFE) is capable of inducing cell-cycle arrest and apoptosis in colorectal cancer cells, implying that LFE could be applied as an anti-neoplasm agent. Longan seed extract (LSE) systemically inhibits colorectal, lung, liver, cervix, and breast cancer cells, indicating its utilization in cancer prevention and treatment.
In vitro antiproliferative activity of a polyphenol-rich longan seed fraction was demonstrated in human SW620 colon cancer cell lines. A fraction at 0.5 wt.% was shown to induce weak early apoptosis, and an increase in caspase-3 and caspase-8 activity was observed in SW620 cells following exposure for 24 and 48 hours.
Studies related to covalent selenized longan polysaccharides confirmed anti-cancer activity, with cancer cell inhibition reaching 10.80%–39.60% after treatment at 50–800 μg/mL for 24 hours. Polysaccharide induced apoptosis in colon cancer cells through activation of death receptors, mitochondria-dependent, and endoplasmic reticulum stress pathways.
Flavonoids isolated from longan leaves demonstrated potent inhibitory effects on colorectal cancer cell proliferation, colony formation, migration, and apoptosis through in vitro assays. Using network pharmacology, molecular docking, and dynamics simulations, afzelin, quercitrin, and trifolin were identified as the primary active constituents targeting AKT1.
Evidence strength: All anticancer evidence for longan is restricted to cell lines (in vitro) and animal models. There are no human clinical trials. While the mechanistic and preclinical data are extensive and internally consistent, no conclusions about efficacy in humans can yet be drawn.
5.5 Anti-obesity and Lipid Metabolism
Longan pericarp polyphenol extract (LPPE) supplementation prevented body weight gain and decreased serum and liver lipids in high-fat diet-induced obese mice. A study published in the Journal of Agricultural and Food Chemistry investigated anti-obesity and hypolipidemic effects of polyphenol-rich longan flower water extract in hypercaloric-dietary rats, finding beneficial effects on lipid parameters.
One study investigated whether longan fruit extract (LE) supplementation can improve diabetic hyperglycemia through modulation of the feeding center located in the hypothalamus of db/db type 2 diabetic mice. LE supplementation ameliorated fasting blood glucose levels and reduced excessive epididymal fat accumulation.
Evidence strength: Rodent model studies only. No human clinical trials on longan for obesity or lipid control have been identified. Evidence is preliminary and limited to preclinical settings.
5.6 Antidiabetic and Anti-hyperglycemic Activity
Studies indicate that the longan peel and seeds are rich in polyphenols, flavonoids, and polysaccharides with antioxidant, antityrosinase, antibacterial, antifungal, antidiabetic, and other activities. Flavonoids in the seed and alkaloids in the pericarp showed potential to be developed as anti-hyperglycemic agents.
Evidence strength: Antidiabetic effects are supported by in vitro enzyme inhibition studies and animal models. As with other areas, human clinical data are absent.
5.7 Anti-inflammatory Activity
Studies have examined the antioxidant and anti-inflammatory activities of the water extract of longan pericarp (WLP), demonstrating significant anti-inflammatory effects. These findings have been replicated across multiple plant parts, including seed, pericarp, and flower extracts, using cell-based and rodent models of inflammation.
Evidence strength: Robust in vitro and animal-model evidence. Human clinical evidence is not available.
5.8 Sleep and Anxiolytic Effects
Longan flower extract (LFE), traditionally used in East Asian medicine, has shown potential health benefits but remains scientifically underexplored. A 2025 study aimed to investigate the chemical composition and bioactive effects of LFE on inflammation, oxidative stress, and melatonin biosynthesis in relevant cellular models.
LFE was prepared using ethanol extraction and characterized for its total polyphenols, flavonoids, oligomeric proanthocyanidins (OPCs), and corilagin content via HPLC. Its anti-inflammatory, antioxidant, and neuroregulatory activities were assessed in LPS-stimulated RAW 264.7 macrophages and BV-2 microglial cells.
Evidence strength: Sleep-related effects (melatonin pathway involvement) are currently only at the in vitro cell model stage. Traditional use precedent exists, but modern clinical corroboration is lacking.
6. Body Systems and Health Areas Associated with Longan
- Cardiovascular / hematological system: Longan fruit is used for enhancing memory, promoting blood metabolism, relieving insomnia, and preventing amnesia. In TCM, it is specifically indicated for heart blood deficiency, palpitations, and anemia.
- Central nervous system: Neuroprotective effects in Parkinson's disease models and cognitive/memory enhancement have been documented in animal and in vitro studies, linked to polysaccharide and polyphenol content.
- Immune system: Dried longan pulp has been used as a traditional Chinese medicine for thousands of years to enhance immunity and treat diseases. Polysaccharide-protein complexes activate NK cells, macrophages, and lymphocytes in vitro and in vivo (animal).
- Gastrointestinal system: Longan polysaccharides have shown the ability to regulate the dynamic balance of intestinal flora.
- Metabolic system: Animal-model evidence implicates longan extracts in improving glucose homeostasis, reducing adiposity, and lowering lipids via PPARα and LXRα pathways.
- Oncological (preclinical): Cell-line and animal evidence for anticancer activity across colorectal, lung, liver, cervical, and breast cancer cell types.
- Skin / cosmeceutical: Seed extract is suggested as a cosmeceutical active ingredient due to anti-hyaluronidase and antioxidant activities.
7. Dosage Forms and Dosages Reported in Studies
No standardized human clinical dosages have been established for longan or its extracts, as no rigorous dose-finding clinical trials have been published in the indexed literature. The following doses are those reported in specific preclinical research and are provided solely as documented in those sources.
- In an immunosuppressed mouse model, peroral administration of LP3 (longan pulp polysaccharide-protein complex) at 100 mg/kg/day significantly enhanced immune parameters, with effects also observed at 50 and 200 mg/kg/day.
- Administration of water extract of longan pericarp (WLP) in the range of 100–400 mg/kg showed concentration-dependent inhibition of carrageenan-induced paw edema in mice.
- Longan flower water extract was administered at 500 mg/day (ex vivo brain study) and at 125–500 mg/kg/day orally in the Parkinson's rat model.
- In toxicological studies, longan extract at a normal dosage of 4 g/kg and two excess dosages of 8 and 16 g/kg was orally administered to mice for two weeks to evaluate dose-related effects on gut homeostasis.
- In studies with selenized longan polysaccharides, cancer cell inhibition in colon cancer cells was observed at concentrations of 50–800 μg/mL over 24 hours.
In TCM herbal preparations, the fruit (long yan rou) is the most frequently used part, typically prepared as decoctions, tonic soups, or dried-fruit infusions, but standardized extract doses in herbal medicine practice are not reported in the peer-reviewed literature reviewed here.
8. Safety Considerations
General Tolerability
In clinical reports, longan arillus is well-tolerated at normal doses in humans, with very few cases of allergy reported from orally taking longan fruit. One report demonstrated that the sugar extract of fresh longan pulp had no acute (at 20 g/kg) and chronic toxicity (at 2.5 g/kg) in rats.
In formal acute toxicity studies, longan sugar extract did not cause mortality or abnormalities. In chronic toxicity studies, all values were normal and no histopathological abnormalities were found.
Excessive Intake and "Shanghuo" Syndrome
The excessive intake of longan fruits or dried longan has been found in daily life to cause "shanghuo," a status described by TCM theory with typical symptoms of oral dryness, oral ulcers, gum bleeding, and swelling. "Shanghuo" is a concept that describes an abnormal internal status, manifested by disruption of microenvironment homeostasis and induction of inflammation.
Animal research found that the aggravated colon injury from excessive longan intake in colitic mice was tightly correlated with altered microbial communities and decreased short-chain fatty acid (SCFA) production. Excessive longan intake disturbs gut homeostasis and aggravates colitis via promoting inflammation and altering gut microbe compositions and associated metabolism in mice.
However, longan intake at a normal dose did not promote colitis in mice.
TCM Cautions
Like the fresh fruit, dried longan is considered heating in TCM, so it should be consumed in moderation; too much can cause insomnia, coughs, and nosebleeds according to TCM principles.
Evidence Gaps and Limitations
No interaction studies between longan preparations and pharmaceutical drugs appear in the peer-reviewed indexed literature. As a food consumed across Asia for millennia, longan pulp is generally recognized as safe at dietary quantities. However, concentrated extracts — particularly polysaccharide fractions, seed extracts, or pericarp extracts used as supplements — have not undergone systematic human safety evaluation. As a treating agent, longan has displayed many biological activities, including anti-proliferative, antioxidant, and anti-cancer activities, but the translation of these effects to human supplemental contexts requires formal clinical investigation. Further research is needed to explore longan's full potential in global health.
References
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