The structure elucidation, anti-aging and hypoglycemic effects of an O-acetyl mannoglucan from the bulbs of Lanzhou lily

Abstract

An O-acetyl mannoglucan (BHP-1) from Lanzhou lily bulbs was structurally elucidated using partial acid hydrolysis, GC–MS, and 2D NMR techniques (COSY, NOESY, HSQC and HMBC) built on prior research, revealing a backbone of -α-D-(1 → 4)-Glcp-β-D-(1 → 4)-Manp- with the most potential side chains -α-D-(1 → 4)-Glcp-β-D-(1 → 4)-Manp-α-D-(1 → 4)-Glcp-α-D-(1 → Glcp- and -α-D-(1 → 4)-Glcp-β-D-(1 → 4)-Manp-α-D-(1 → Glcp-, attached to O-2 and O-3 of glucose and mannose residues, and featuring O-acetyl groups at O-2 or O-3 position of mannose. The terminal residue was α-D-(1 → Glcp. BHP-1 demonstrated anti-aging and hypoglycemic effects, as assessed by C. elegans model and glycolytic enzyme effect in vitro, respectively. The results showed that BHP-1 dose-dependently prolonged lifespan of C. elegans by 33 % at 4 mg/mL under normal conditions, with greater extensions under thermal and oxidative stress (50 % and 80 % increases, respectively, p < 0.05), which were attributed to enhanced antioxidant enzymes (SOD and CAT) and lowered MDA levels of C. elegans. Additionally, BHP-1 exhibited remarkable inhibition on α-glucosidase (93 %) and moderate inhibition on α-amylase (53 %) at 4 mg/mL, with competitive inhibition of α-glucosidase and mixed non-competitive inhibition of α-amylase, respectively. These potential effects might be linked to BHP-1's diverse sugar linkages, higher content of Glc, and certain O-acetyl contents.