Antiproliferative, anti-inflammatory and antioxidant activity of Ptaeroxylon obliquum leaf extracts and fractions

Abstract

Ptaeroxylon obliquum (Thunb.) Radlk. (Rutaceae) is traditionally used in South Africa to treat many ailments including inflammation-related diseases. Approximately 20% of cancers are induced by chronic inflammation or other infections. In this study, in vitro antiproliferative, anti-inflammatory and antioxidant activity of P. obliquum acetone and aqueous leaf extracts and fractions prepared using column chromatography were determined. Antiproliferative activity was evaluated against Vero cells, human breast cancer (MCF-7), hepatocarcinoma (HepG2), lung adenocarcinoma (A549) and human cervical cancer cells (Hela) using a colorimetric tetrazolium bromide assay. Soybean 15-lipoxygenase (15-LOX) inhibitory assays were used to evaluate the anti-inflammatory activity. Radical scavenging activity was tested using 2, 2-diphenyl-1-pircrylhydrazyl (DPPH) and 2, 2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. Water extracts scavenged ABTS radicals with IC50 values as low as 29 µg/ml. Acetone extracts and fractions had good activity against 15-LOX with IC50 values of 6 – 10 µg/ml and 22 – 23 µg/ml respectively. Most acetone extracts were toxic to HepG2 cells with LC50 values from 2.2 – 10 µg/ml and were less toxic to other cell lines including non-cancerous Vero cells, with promising selectivity index values ranging from 5 to 22. Aqueous extracts and fractions were non-toxic at the concentrations tested against all the cell lines. Morphological analysis of HepG2 and Hela cells using light microscopy showed that acetone extracts changed the morphology of the cells, and further investigation is ongoing. The acetone extract had selective antiproliferative and anti-inflammatory activity, supporting the use of P. obliquum in traditional medicine against inflammatory-related diseases including cancer.