In vitro anti-prostate cancer and ex vivo antiangiogenic activity of Vernonia guineensis Benth. (Asteraceae) tuber extracts

Ethnopharmacological relevance

Prostate cancer is a major problem worldwide and affects most men above the age of forty-five. Vernonia guineensis Benth. (Asteraceae) root decoction is used in folk medicine in Cameroon to treat a number of ailments including prostate cancer. The aim of this study was to provide a preliminary validation of the use of Vernonia guineensis Benth. extracts to treat prostate cancer by evaluating the in vitro activity of its crude extracts and isolated molecules on prostate cancer cells lines and effect on angiogenesis which is essential for growth and metastases of prostate cancer.

Materials and methods

Aqueous, dichloromethane and methanol extracts of Vernonia guineensis Benth. tubers were tested for activity against three prostate cancer cell lines (PC-3, DU-145 and AT3B-1). The dichloromethane extract was subjected to bioactivity guided fractionation. Anti-proliferation, clonogenic and antiangiogenic activity of the crude extracts and isolated compound were tested. The WST-1 assay was used for the anti-proliferation activity meanwhile the standard clonogenic test and the rat ring aorta assay were carried out to determine the clonogenic and antiangiogenic activity of tested products respectively.

Results

The aqueous and methanol extracts of Vernonia guineensis Benth. demonstrated weak activity against prostate cancer cell lines in vitro with IC₅₀ > 100 μg/mL. The dichloromethane extract was more potent with IC₅₀ of 56.233 ± 3.630 μg/ml and 67.316 ± 2.452 μg/ml against the DU-145 and PC-3 cell lines respectively. Activity guided fractionation of this extract yielded a Pentaisovalerylsucrose (1) isolated for the first time from a natural source to the best of our knowledge. Compound 1 demonstrated in vitro activity against the human prostate cancer cell lines PC-3 and DU-145 with IC₅₀ of 5.701 ± 0.142 μM and 4.275 ± 0.710 μM, respectively. The IC₅₀ of the compound was 5.763 ± 0.425 μM against AT3B-1, a rat prostate cancer cell line expressing P-glycoprotein which is linked to drug resistance in most metastatic cancers. Compared to compound 1, Paclitaxel and Docetaxel were active against AT3B-1 at 2.641 ± 1.253 μM and 0.613 ± 0.251 μM. Paclitaxel showed IC₅₀ values of 0.004 ± 0.002 μM and 0.003 ± 0.001 μM against DU-145 and PC-3 prostate cancer cell lines respectively. Docetaxel showed IC₅₀ values of 0.002 ± 0.001 μM and 0.004 ± 0.001 μM against DU-145 and PC-3 prostate cancer cell lines respectively.

Conclusion

The in vitro anti-prostate cancer and the antiangiogenic activity of Vernonia guineensis Benth. extracts and isolated compound support the use of the tubers of this plant for the treatment of prostate cancer.