Antioxidants and α-glucosidase inhibitors from “Liucha” (young leaves and shoots of Sibiraea laevigata)

- Twenty-five phenolic compounds were isolated and identified from “Liucha”.
- Twenty-three compounds were reported from Sibiraea laevigata for the first time.
- Phenolic compounds showed potent α-glucosidase inhibition and antioxidant activities.
- Sorbitol ester F showed the best α-glucosidase inhibitory activity in vitro.

The young leaves and shoots of Sibiraea laevigata, known as “Liucha”, are used as tea by Tibetans to improve digestion after meals. Long-term consumption of “Liucha” will cause weight loss. In present work, we reported on the isolation and NMR and chemical analysis-based elucidation of seven new sorbitol O-caffeic acid ester derivatives named sorbitol esters A-G (1-7) and eighteen known phenolic compounds from S. laevigata. All of the isolates were evaluated for their antioxidant and α-glucosidase inhibitory activities. Among them sorbitol ester A (1), sorbitol ester D (4), sorbitol ester F (6), sorbitol ester G (7), isoferulic acid (15), methyl caffeate (18), trans-p-hydroxycinnamic acid (19), and kaempferol 3-O-β-d-(6″-E-p-coumaroyl)-glucopyranoside (25) showed more potent α-glucosidase inhibitory activity than the clinical drug acarbose.