a-Glucosidase inhibition, anti-glycation and antioxidant activities of Liquidambar formosana Hance leaf, and identification of phytochemical profile

This study firstly investigates the ability of Liquidambar formosana Hance leaf (LFHL) against diabetes and diabetic complications. The bio-active constituents in LFHL extract were fractionated with solvents at various polarities. The antioxidant, hypoglycemic and anti-glycation activities, and the content of phenolics, flavonoids, hydrolysable tannins and condensed tannins were measured. The phytochemical profile of which gave the highest activity was identified by using HPLC-QTOF -MS/MS. Results revealed that the ethyl acetate fraction (EAF) gave the richest phenolics, condensed tannins and hydrolysable tannins, which was 5.06, 8.75 and 3.57 fold of that of crude extract, respectively. The highest total flavonoids content was detected in n-butanol fraction. The EAF also exhibited the strongest antioxidant, hypoglycemic and anti-glycation activity. The DPPH·scavenging ability, a-glucosidase and advanced glycation end-products formation inhibitory percentage was 1.74, 168.19 and 2.51 fold of that of individual positive control. Totally, 22 compounds were identified or tentatively identified from the EAF of LFHL extract, including 7 phenolic acids, 4 flavanols, 9 flavonols, 1 tannin, and 1 lignan. Above results indicated that LFHL can be a potentially alternative source of products against diabetes and diabetic complications.