Longan Arillus: A comprehensive review of botany, traditional uses, phytochemistry, pharmacologic activities, pharmacokinetics, quality control, toxicity, and clinical applications.

ETHNOPHARMACOLOGICAL RELEVANCE: Longan Arillus (LA) is the aril of Dimocarpus longan Lour. of the Sapindaceae family, commonly known as Guiyuan, whose first documentation can be traced back to the ancient book "Shen Nong's herbal classic". Since ancient times, LA has been commonly used in combination with other herbs or ingredients to make a variety of formulas and medicinal products, which were used to treat diseases such as insomnia, forgetfulness, neurasthenia, overthinking, fatigue, and deficiency of qi and blood, e.g., "Gui Spleen Tang", "Yu Ling Cream", "An Shen Ding Zhi Pill", etc. AIM OF THE REVIEW: This paper presents a comprehensive review encompassing LA's traditional usage, quality control, botany, phytochemical constituents, pharmacological activities, toxicological profiles, pharmacokinetic properties, and clinical applications. The aim is to provide an extensive overview of the current research landscape, facilitating further exploration and utilization of LA resources.

MATERIALS AND METHODS: This article uses "Dimocarpus longan Lour." and "Longan Arillus" as the keywords and collects relevant information on LA from different databases, including PubMed, Web of Science, X-mol, Sci-finder, SCI-HUB, CNKI, Chinese Masters and Doctoral Dissertations, Wanfang Data, Baidu Scholar, Google Scholar, ancient material medica and the Pharmacopoeia of the People's Republic of China (2020).

RESULTS: To date, a total of 378 compounds have been identified in LA, including 12 sugars, 28 polyphenols, 234 volatile components, 12 terpenes and steroids, 28 organic acids, 15 lipids, 11 nucleosides, 32 amino acids and 6 others compounds. Among them, polysaccharides and polyphenols are its main active ingredients. LA has a variety of biological activities, such as immunoregulatory activity, inhibition of Alzheimer's disease, anti-inflammatory, anti-tumor, antioxidant, and inhibition of osteoporosis. In particular, immunomodulatory effects have received much attention. Pharmacological studies have shown that LA enhances immunomodulatory activity through signaling pathways such as MAPK, PI3K/Akt, NF-κB, and MyD88/TRAF6. In addition, this paper reveals the shortcomings of current LA research and its possible future research directions.

CONCLUSIONS: This paper provides a comprehensive review of LA and highlights its multiple pharmacological activities, particularly immunomodulatory effects. However, the current in vivo and clinical studies of LA are relatively limited. Consequently, the scope of in vivo and clinical studies should be expanded in the future. In addition, it is highly recommended that further research efforts be directed towards pharmacokinetics and quality control of LA, and a reference for future studies on clinical application and new product development of LA.