Abstract:
Several cancers are induced by microbial infections or chronic inflammation. Ptaeroxylon
obliquum is traditionally used to treat various infections characterized by inflammation. The in vitro
antiproliferative and antioxidant activity of P. obliquum leaf extracts, fractions and isolated compounds
were determined. Antiproliferative activity was assessed against normal Vero cells, and several
cancerous human cells, including human breast cancer (MCF-7), hepatocarcinoma (HepG2), lung
adenocarcinoma (A549) and human cervical cancer cells (HeLa) using a colorimetric tetrazolium
bromide assay. Radical scavenging activity was tested using the 2,2-diphenyl-1-instrpicrylhydrazyl
(DPPH) and 2,2’-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. Obliquumol, Omethylalloptaeroxylin
and a mixture of lupeol and -amyrin were isolated from the chloroform
fraction using silica gel open column chromatography. Acetone extracts were toxic to HepG2 cells
with IC50 values from 8 to 200 g/mL but were less toxic to other cells with selectivity index as high
as 14. Aqueous extracts and fractions were non-toxic at concentrations tested against all the cell lines
(IC50 > 100 g/mL). Isolated compounds had IC50 values ranging from 52 to 539 g/mL and 189
to 247 g/mL against HepG2 and HeLa cells, respectively. Light microscopy showing changes in
HepG2 and HeLa cell morphology supported the cytotoxicity of the acetone extracts. Water extracts
scavenged ABTS and DPPH radicals with IC50 values as low as 29.06 g/mL and 43.4 g/mL. P.
obliquum extracts may be useful as sources of anticancer therapy, as they have selective cytotoxicity
against cancer cell lines.
