Labdane diterpene lactones of Vitex pubescens and their antileukemic properties

Vitex pubescens belonging to the Verbenaceae family, has been historically used as a folk medicine in Indonesia. The dichloromethane extract of V. pubescens stembarks interfered cell proliferation and induced apoptosis in human leukemia HL-60 cells. Our phytochemical investigation resulted in the isolation of several constituents and their chemical structures were determined by spectroscopic analyses. Upon treatment with labdane diterpene lactones, relatively high inhibition of cell proliferation and apoptotic response of the cells were observed. Furthermore, the structure-activity relationship analysis with clerodane diterpenes revealed that a γ-butyrolactone ring contributes their antileukemic potency. Overall, these findings enhanced the ethnopharmacological relevance of V. pubescens for cancer chemotherapy.