Two flavanone compounds from litchi (Litchi chinensis Sonn.) seeds, one previously unreported, and appraisal of their α-glucosidase inhibitory activities

Using a bioactivity-guided method, a new and a previously reported flavanone glycoside were isolated from 50% ethanol extract of litchi (Litchi chinensis Sonn.) seeds. Column chromatography using macroporous resin, silica gel and Sephadex LH-20 was applied during the isolation, and the method of PMP derivatisation was performed to investigate the component sugar of the compounds. The structures of the compounds were elucidated by 1H, 13C, and 2D NMR (HMQC, HMBC) spectroscopy and HR-ESIMS. Compound 1 was identified as (2R)-naringenin-7-O-(3-O-α-l-rhamnopyranosyl-β-d-glucopyranoside), a new, natural product that had been synthesised previously. Compound 2 was (2S)-pinocembrin-7-O-(6-O-α-l-rhamnopyranosyl-β-d-glucopyranoside). The two isolated compounds showed activity in the α-glucosidase inhibition assay.

Research highlights
► Research on α-glucosidase inhibitory activity in litchi seeds.
► Two flavanone glycosides, which one was novel, were identified by NMR.
► The PMP derivatisation method was performed to investigate the component sugar.
► The two compounds showed activity in the α-glucosidase inhibition assay.