A new pyrrolopyrazine alkaloid from the fruit of Lycium chinense

A new pyrrolopyrazine alkaloid, named lycipyrazine A (1), alone with seven known alkaloids (2-8), were isolated from the fruit of Lycium chinense. The structure of new compound 1 was determined using extensive 1D and 2D spectroscopic analyses, while its absolute configuration was determined by comparison of its experimental and calculated ECD spectra. Their alpha-glucosidase inhibitory activity was screened using acarbose as a positive control. Compound 4 showed strong inhibitory activity against alpha-glucosidase (IC50 = 3.04 +/- 0.38 mu M). This study enriched the structural diversity of alkaloids in L. chinense and provided further clues for searching new antidiabetic agents from natural sources.