In Vitro Antiproliferative Activity of Ptaeroxylon obliquum Leaf Extracts, Fractions and Isolated Compounds on Several Cancer Cell Lines
2022
Edward T. Khunoana | Jacobus N. Eloff | Thanyani E. Ramadwa | Sanah M. Nkadimeng | Mamoalosi A. Selepe | Lyndy J. McGaw
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&rsquo:-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. Obliquumol, O-methylalloptaeroxylin and a mixture of lupeol and &beta:-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 µ: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 µ:g/mL). Isolated compounds had IC50 values ranging from 52 to 539 µ:g/mL and 189 to 247 µ: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 µ:g/mL and 43.4 µ:g/mL. P. obliquum extracts may be useful as sources of anticancer therapy, as they have selective cytotoxicity against cancer cell lines.
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