Bioactivity guided isolation of cytotoxic terpenoids and steroids from Premna serratifolia

Abstract

Context: Despite several phytochemical studies of Premna serratifolia Linn. (Verbenaceae), the isolation of active constituents of this plant remains to be explored. Objective: The study isolates cytotoxic terpenoids and steroids from the leaves of Premna serratifolia. Materials and methods: Unsaponifiable matter of hexane soluble fraction obtained from methanol extract was subjected to isolation by column chromatography and preparative TLC. Three compounds PS-01 A, PS-01B and PS-02 A were isolated. PS-01 A and PS-01B were identified by comparative TLC with authentic marker compounds followed by NMR analysis. Further PS-01B was analyzed by HR-GCMS. PS-02 A was subjected to HR-LCMS. All isolated compounds/fractions were evaluated for cytotoxic activity by BSL bioassay and using cell lines A549, HepG2 and L6. Results: Three compounds were isolated from the leaf extract by bioactivity-guided fractionation. Two of which, namely, PS-01 A (oleanolic acid) and PS-02 A (unknown) were found to be terpenoids and PS-01B was identified as steroid (stigmasterol). PS-02 A compound is to be purified and characterized further. All three compounds PS-01 A, PS-01B, PS-02 A showed cytotoxicity by BSL bioassay (LC50 value of 54.49, 30.83, 16.32 ppm, respectively) and by cell line study where isolate PS-02 A has shown more cytotoxicity with LC50 values of 66.77 and 53.72 μg/mL with A549 and HepG2 cells, respectively, when compared with other isolates. Conclusion: Bioactivity guided fractionation of Premna serratifolia leaves succeeded into isolation of two terpenoids and one steroid compound with significant cytotoxic activity. Here we report the isolation of these cytotoxic terpenoids/steroids from this plant for the first time which could be developed as anticancer agents.

Keywords

• fractionation
• column chromatography
• preparative tlc
• bsl bioassay
• cell line studies