Anti-inflammatory potential of South African medicinal plants used for the treatment of sexually transmitted infections

Abstract

Inflammation associated with sexually transmitted infection (STIs) often results from delayed diagnosis or treatment, and may result in life-threatening complications. The root or stem bark of plants selected in this study are used by traditional healers in the management of STIs and to treat the associated inflammation. This study evaluated the anti-inflammatory activities of 12 South African medicinal plants used traditionally in the treatment of STIs and the associated inflammation. Acetone extracts were tested for anti-inflammatory activity against 15-lipoxygenase (15-LOX), xanthine oxidase (XO) and inducible nitric oxide production in lipopolysaccharide (LPS) stimulated RAW 264.7 macrophage cells. The free radical and nitric oxide scavenging capacity was determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and nitric oxide inhibition assays. The MTT assay was used to determine the cytotoxic effect of the extracts on RAW 264.7 macrophages and Vero cells. Preliminary phytochemical analysis was carried out using NMR spectroscopy, Gas Chromatography Mass Spectroscopy (GC–MS) analysis and the determination of total phenolic and flavonoid contents. The root bark extract of Lannea schweinfurthii had the highest inhibitory activity against 15-LOX (IC50 = 40 ± 3 μg/mL) while C. abbreviata best inhibited XO (IC50 = 46.8 ± 1.5 μg/mL). Extracts of Ficus abutilifolia, Faurea saligna and Zanthoxylum capense showed significant suppression of inducible nitric oxide production with IC50 values comparable to quercetin (IC50 < 30.0 μg/mL). The extracts of C. abbreviata and F. abutilifolia had significantly higher radical scavenging activities compared to ascorbic acid. Most of the extracts showed little or no cytotoxicity against the tested cell lines. Phytochemical analysis pointed to the presence of diverse classes of secondary metabolites as well as the presence of proanthocyanidins as the major constituents of the most active extracts in the anti-inflammatory assays. For most of the plants, this study provides the first report of 15-LOX inhibition and xanthine oxidase inhibition. The activity of most of the tested extracts supports the administration of these plants by traditional healers in the treatment of STIs and their associated inflammation.