We extracted one new C-methyl flavonoid, farrerol 7-O-beta-D-(6-O-galloyl) glucopyranoside (1), along with 11 known flavonoids, from the Cleistocalyx (C.) conspersipunctatus leaves. Elucidation of these flavonoid structures was accomplished through spectroscopic investigation and electronic circular dichroism (ECD) computation. Compared to corosolic acid (IC50: 15. 5 & PLUSMN; 0.9 mu M), an established inhibitor, the compound 1 (IC50: 6.9 & PLUSMN; 1.2 mu M) was found more active in suppressing alpha-glucosidase. These findings imply the potential of compound 1 as a valid alpha-glucosidase inhibitor, which also offer evidence for future animal experiments and clinical trials. Besides, molecular docking was employed to explore the probable mechanism for alpha-glucosidase- compound 1 interaction. The biosynthetic pathway of these flavonoids in C. conspersipunctatus were proposed.& nbsp;(c) 2022 The Authors. Published by Elsevier B.V. on behalf of King Saud University.& nbsp;