Antihyperglycemic and anti-type 2 diabetic activity of marine hydroquinone isolated from brown algae (Dictyopteris polypodioides)

BACKGROUND AND AIMS: Brown algae (Dictyopteris polypodioides) extract (DP) presented high inhibitory potential against α-amylase. The present study aims to isolate, purify and evaluate the antihyperglycemic and anti-type 2 diabetic activities of marine hydroquinone from DP. METHODS: Marine hydroquinones were isolated using silica gel, HPLC, and NMR spectroscopy was used to identify compound 1 and compound 2 as zonarol and isozonarol, respectively. The anti-hyperglycemic and anti-type 2 diabetic activities of zonarol were investigated by in vitro assay (α-amylase, α-glucosidase), Lineweaver–Burk plot and Type 2 diabetes mellitus model (T2DM) mice induced by streptozotocin (STZ). RESULT: Zonarol had the highest content and the strongest inhibitory activity against α-glucosidase (IC(50) value of 6.03 mg L(−1)) and α-amylase (IC(50) value of 19.29 mg L(−1)) in a competitive inhibition and mix-type manner, respectively. The maltose and starch loading tests revealed that zonarol significantly reduced postprandial glycemia after 30 min loading (9.12 and 8.12 mg/dL, respectively), compared to normal (11.37 and 12.37 mg/dL, respectively). Zonarol exhibited pancreatic islet cell rejuvenation, as evidenced by increased pancreatic islet mass, and hence helps in the restoration of insulin levels and therefore improves the glucose metabolism in STZ-induced diabetic mice. Zonarol treatment in T2DM elevated abundant levels of main SCFAs (propionate, butyrate, and valeric acid), which are closely related to glucose metabolism homeostasis. CONCLUSION: Our finding indicates that zonarol could be used as a food supplement to treat hyperglycemia and diabetes.