Anti-diabetic activities of cis- and trans-2,3,5,4′-tetrahydroxystilbene 2-O-β-glucopyranoside from Polygonum multiflorum

Scope: Functional foods can be used alone or in combination with existing therapies in preventing and treating type 2 diabetes (T2D). Trans-2,3,5,4'-tetrahydroxystilbene 2-O-beta-glucopyranoside (trans-THSG), a dominant bioactive compound from Polygonum multiflorum (PM)-a popular medicinal food in Asia, has attracted increasing research interests due to its strong antioxidant activity. The content of naturally occurring cis-THSG (cis-2,3,5,4'-tetrahydroxystilbene 2-O-beta-glucopyranoside) was very low in PM root, but was prepared in this study by mimicking the traditional process of PM. The anti-diabetic effects of trans-and cis-THSG were evaluated in T2D to search for more efficacious food ingredient(s). Methods and results: Trans-THSG was chromatographically purified from PM roots and cisTHSG was prepared with our innovative process via exposure of trans-THSG to UV-light. The anti-diabetic effects of both THSGs were tested with HFD-induced male CF-1 diabetic mice. Cis-THSG was found more effective than trans-THSG in hypoglycemic effect and in ameliorating glucose intolerance and insulin resistance. In HepG2 cells, cis-THSG also demonstrated more potent activity than trans-THSG in suppressing transcription of phosphoenopyruvate carboxykinase (PEPCK). Conclusion: Cis-THSG can be an enriched bioactive ingredient in PM roots from postprocessing and is significantly more effective against hyperglycemia than trans-THSG. One of the effective pathways was through inhibition of PEPCK.