Longan Tree

The Longan Tree (Dimocarpus longan), an evergreen fruit tree from the family Sapindaceae, originally comes from southern China and northern Thailand but is now cultivated in large parts of Southeast Asia, in Hawaii, and in subtropical regions. The round, brownish fruits contain a translucent, juicy flesh whose taste is reminiscent of lychee. The name "Longan" derives from the Cantonese "lùhng ngáahn," which means "dragon's eye" – an allusion to the dark, round seed surrounded by pale flesh. The longan has held significance in Chinese culture and medicine for thousands of years. In Traditional Chinese Medicine (TCM), the fruit is considered tonifying, blood-strengthening, and calming to the nerves. It is consumed both fresh and dried and plays a role in numerous rituals, festive meals, and healing recipes.

What health benefits does the Longan Tree offer?

The fruit of the Longan Tree has long been regarded in traditional medicine as a potent remedy for various health problems. Studies likewise point to great medicinal potential; however, some of them should be viewed critically, as they are not readily transferable or were conducted with animals. In general, more research is needed before definitive statements can be made. Here are some of the findings to date

  • Rich in antioxidants: Longan fruits contain high amounts of vitamin C as well as secondary plant compounds such as polyphenols and flavonoids, which can neutralize free radicals and thus counteract oxidative stress (1,2,3).
  • Anti-inflammatory effects: The longan fruit has shown anti-inflammatory properties in investigations, which points to its potential as a natural anti-inflammatory agent (1,2,4).
  • Immune system support: Due to the high vitamin C content, regular consumption can strengthen the immune defense and promote wound healing (2,5).
  • Antimicrobial effects: Studies point to an antimicrobial and antifungal effect that appears to originate from the seed of the fruit (2,6,7).
  • Anti-osteoporosis effects: Extracts from the fruit inhibited osteoclast differentiation by suppressing osteoclast-specific markers while at the same time promoting osteoblast differentiation and the growth of chondrocytes (2,8,9).
  • Anti-tyrosinase activity: The extract from the longan fruit peel, especially when obtained through ultrasound- or high-pressure-assisted processes, shows a strong, concentration-dependent inhibition of tyrosinase activity, which works by binding to the active site of the enzyme (1,2).

How does the Longan Tree work in the body?

The health-promoting effects are based primarily on the combination of various active compounds such as vitamin C, polyphenols, and polysaccharides (1,2). These substances are well researched and bring with them a whole range of potential effects. In TCM, longan is classified as a "warming" food that is said to strengthen Qi energy, improve blood circulation, and calm the "Shen" (spirit/heart).

Are there any risks or side effects?

  • High sugar content: Fresh and dried longans contain a relatively large amount of fructose, which can be relevant for diabetics (2).
  • Allergic reactions: In rare cases, skin reactions or intolerances can occur.
  • TCM note: Since longan is considered warming, excessive consumption is not recommended in TCM for people with "inner heat" or acute inflammation (3).

Conclusion

The Longan Tree is not only a culinary delicacy but also an important part of traditional Asian healing arts. Its fruits have shown antioxidant, immune-strengthening, and calming properties in studies and are deeply rooted in the culture of Southeast Asia. Despite the health benefits, consumption – especially in dried form – should be moderate. In addition, more research is needed before definitive statements can be made.

Sources:

  1. Hong-In, P., Neimkhum, W., Punyoyai, C., Sriyab, S., & Chaiyana, W. (2021). Enhancement of phenolics content and biological activities of longan (Dimocarpus longan Lour.) treated with thermal and ageing process. Scientific reports, 11(1), 15977. https://doi.org/10.1038/s41598-021-95605-3
  2. Zhang, X., Guo, S., Ho, C.-T., & Bai, N. (2020). Phytochemical constituents and biological activities of longan (Dimocarpus longan Lour.) fruit: A review. Food Science and Human Wellness, 9(2), 95–102. https://doi.org/10.1016/j.fshw.2020.03.001
  3. Yang, B., Jiang, Y., Shi, J., Chen, F., & Ashraf, M. (2011). Extraction and pharmacological properties of bioactive compounds from longan (Dimocarpus longan Lour.) fruit — A review. Food Research International, 44(7), 1837–1842. https://doi.org/10.1016/j.foodres.2010.10.019
  4. Watson, A. A., Fleet, G. W., Asano, N., et al. (2001). Polyhydroxylated alkaloids – Natural occurrence and therapeutic applications. Phytochemistry, 56(3), 265–295. https://doi.org/10.1016/S0031-9422(00)00451-9
  5. Yi, Y., Zhang, M. W., Liao, S. T., et al. (2012). Effects of alkali dissociation on the molecular conformation and immunomodulatory activity of longan pulp polysaccharide (LPI). Carbohydrate Polymers, 87(2), 1311–1317. https://doi.org/10.1016/j.carbpol.2011.09.014
  6. Rangkadilok, N., Tongchusak, S., Boonhok, R., et al. (2012). In vitro antifungal activities of longan (Dimocarpus longan Lour.) seed extract. Fitoterapia, 83(3), 545–553. https://doi.org/10.1016/j.fitote.2011.12.023
  7. Tseng, H. C., Wu, W. T., Huang, H. S., et al. (2014). Antimicrobial activities of various fractions of longan (Dimocarpus longan Lour. Fen Ke) seed extract. International Journal of Food Sciences and Nutrition, 65(5), 589–593. https://doi.org/10.3109/09637486.2014.886181
  8. Park, S., Kim, J. H., Son, Y., et al. (2016). Longan (Dimocarpus longan Lour.) fruit extract stimulates osteoblast differentiation via Erk1/2-dependent RUNX2 activation. Journal of Microbiology and Biotechnology, 26(5), 1063–1066. https://doi.org/10.4014/jmb.1601.01092
  9. Son, Y., Lee, E. M., Lee, D. Y., et al. (2019). Longan fruit increase bone mineral density in zebrafish and ovariectomized rat by suppressing RANKL-induced osteoclast differentiation. Phytomedicine, 59, Article 152910. https://doi.org/10.1016/j.phymed.2019.152910