Inhibition of CDK2/CyclinE1 by xanthones from the mangosteen (Garcinia mangostana): a structure-activity relationship study

Uncontrolled regulation of cyclin dependent kinases (CDKs) has negative implications in many cancers and malignancies and has recently led to the approval of select CDK inhibitors. Herein we present data reporting that xanthones, a class of compounds isolated from the purple mangosteen (Garcinia mangostana) fruit, can inhibit CDK2/CyclinE1. We evaluated nine different xanthones, including α-mangostin, β-mangostin, γ-mangostin, gartanin, 8-desoxygartanin, garcinone C, garcinone D, 9-hydroxycalabaxanthone, and 3-isomangostin for toxicity in 22Rν1 (prostate cancer cells) and MDA-MB-231 (breast cancer cells). All compounds dose-dependently inhibited the viability of both cell lines. A cell free biochemical assay was performed to determine if selected phytochemicals inhibited CDK2/CyclinE1. γ-Mangostin and α-mangostin were the strongest inhibitors, respectively. The results suggest that the position of key functional groups including hydroxyl and isoprenyl groups contribute to the CDK2 inhibitory effect. Taken together, the evidence suggests that xanthones can directly target CDK2 providing a possible explanation for their therapeutic potential.