Cytotoxic and Neuroprotective Biflavonoids from the Fruit of Rhus parviflora

Six biflavonoids, succedaneaflavanone (1), mesuaferrone B (2), rhusflavanone (3), rhusflavone (4), agathisflavone (5), and cupressuflavone (6), were isolated from the fruits of Rhus parviflora. The chemical structures of the compounds were determined based on NMR, fast atom bombardment mass spectrometry, and IR. Biflavonoid compounds were evaluated for cytotoxicity against human cancer cell lines, including human colon carcinoma (HCT-116), human breast carcinoma (MCF-7), and human cervical carcinoma (HeLa). Biflavonoids 2, 3, and 5 showed significant cytotoxicity with IC50 values of 17.25 μM (mesuaferrone B against HCT-116), 17.50 μM (rhusflavone against MCF-7), and 15.20 μM (agathisflavone against HeLa). Compound 5 showed inhibition of β-secretase activity at a 10 μM concentration. Compound 6 showed inhibition of cyclin-dependent kinases (CDK2 and CDK5) with IC50 values of 18.58 and 9.29 μM, respectively.