ISOLATION OF BIOACTIVE COMPOUNDS FROM CENTAUREA AEGYPTIACA

Abstract

Objective: In a previous study, Centaurea aegyptiaca ethanol and ethyl acetate extracts showed potent cytotoxic effects against laryngeal (HEP2) and hepatic (HEPG2) carcinoma cell lines. Additionally, two novel compounds were isolated and identified. The aim of this study is to continue isolating and identifying another compound (s) that may, also, be responsible for this potent biological activity.Methods: C. aegyptiaca dried aerial parts were extracted with ethanol and ethyl acetate. Both extracts were chromatographed separately to afford seven guaianolides that were identified using different spectroscopic methods. Moreover, compounds 1-7 were evaluated for their cytotoxicity (IC50, µM) against HEP2 and HEPG2 cells in comparison to the normal fibroblasts (BHK) using sulforhodamine B assay. Doxorubicin was used as a positive control.Results: Seven sesquiterpene lactones, centaurepensin, also known as chlorohyssopifolin A (1), 8α-hydroxy-11α, 13-dihydrozaluzanin C (2), chlorohyssopifolin B (3), desacylcynaropicrin (4), chlorohyssopifolin C, acroptilin (5), subluteolide (6), and solstitiolide (7) were isolated from C. aegyptiaca extracts and identified. This is the first report on the occurrence of 2, 4, 5 and 6 in C. aegyptiaca. Compounds 1-4 and 6 exhibited selective cytotoxic effects against HEP2 and HEPG2 cells. However, compounds 1 and 7 showed the highest activities against HEP2 with IC50 values of 10.6±0.02 and 10.9±0.03 µM, respectively. Moreover, compound 3 was the most potent one against HEPG2 cells with IC50value of 13.8±0.05 µM.Conclusions: Chemical investigation of C. aegyptiaca ethanol and ethyl acetate extracts led to the isolation and identification of seven guaianolides. These compounds exhibited good cytotoxic activities against HEP2 and HEPG2 cell lines.