Abstract:Ethanol and aqueous extracts of lychee seeds (Litchi chinensis Sonn.) were obtained by reflux extraction using 70% ethanol and water, respectively. The total phenolic and flavonoid contents were determined using the Folin-Ciocalteu method and NaNO2-Al(NO3)3-NaOH colorimetry. Ethanol and aqueous lychee seed extracts were rich in phenolic and flavonoid compounds. Ultra-high-performance liquid chromatography–quadrupole-orbitrap mass spectrometry was used to identify their chemical compositions. A total of 72 chemical components were identified, including 13 phenolic and 29 flavonoid compounds. The ethanol and aqueous extracts showed significant 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) scavenging activities (2.10 and 6.30 μg/mL, respectively) and 2,2-diphenyl-1-picrylhydrazyl scavenging activities (2.98 and 16.90 μg/mL, respectively). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Griess reagent, and enzyme-linked immunosprbent assays showed that a non-toxic dose of the ethanol extract effectively inhibited the release of nitric oxide, IL-6 and IL-1β in LPS-stimulated RAW264.7 cells. The ethanol and aqueous extracts demonstrated excellent α-glucosidase inhibitory activities (0.14 and 6.03 μg/mL, respectively), superior to that of the positive control, acarbose (189.40 μg/mL). The ethanol extract exhibited strong tyrosinase inhibitory activity (139.85 μg/mL), which was significantly better than that of the positive control, arbutin. Moreover, the ethanol extract exhibited remarkable acetylcholinesterase (34.91 μg/mL) and butyrylcholinesterase (21.91 μg/mL) inhibitory activities. In summary, lychee seeds are rich in phenolic and flavonoid compounds and has antioxidant, anti-inflammatory, hypoglycemic, whitening, enzyme inhibitory, and anti-Alzheimer’s disease properties. These results provide a theoretical basis for the development and utilization of lychee as a source of active ingredients in the fields of cosmetics, functional foods, and pharmaceuticals.
