BackgroundInflammation is a common risk factor in the pathogenesis of conditions such as infections, arthritis, type 2 diabetes mellitus, obesity and cancer. An ethnobotanical survey of medicinal plants used traditionally to treat inflammation and related disorders such as pain, arthritis and stomach aches in southern Africa led to the selection of 25 plant species used in this study.MethodsThe antioxidant activities of acetone extracts were determined by measuring the free radical scavenging activity and ferric reducing ability, respectively. The anti-inflammatory activities of the extracts were determined by measuring the inhibitory effect of the extracts on the activities of the pro-inflammatory enzyme, lipoxygenase and inducible nitric oxide synthase.ResultsExtracts of Peltophorum africanum had good antioxidant activity with IC50 values of 4.67 ± 0.31 μg/mL and 7.71 ± 0.36 μg/mL compared to that of the positive control ascorbic acid (2.92 ± 0.14 μg/mL and 13.57 ± 0.44 μg/mL), using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging and 2,2′-azinobis (3-ethylbenzthiazoline-6-sulphonic acid (ABTS) methods, respectively. The metabolism of linoleic acid to leukotriene derivatives by 15-lipoxygenase (15-LOX) was also inhibited by the crude acetone extracts of Peltophorum africanum (IC50 = 12.42 μg/mL), Zanthoxylum capense (IC50 = 14.92 μg/mL) compared to the positive control quercetin (IC50 = 8.75 μg/mL). There was a poor correlation between the flavonoid content and 15-LOX inhibition by the extracts (R2 = 0.05), indicating that flavonoids are not involved in LOX inhibition. Extracts of Clausena anisata, at a concentration of 6.25 μg/mL inhibited nitric oxide production by RAW 264.7 macrophage cell lines in vitro by 96 %. The extracts of Zanthoxylum capense were the least cytotoxic (IC50 > 1000 μg/mL) when the extract toxicity was determined against Vero (African green Monkey) kidney cell lines.ConclusionSome plant species used traditionally to treat pain have reasonable anti-inflammatory activity and flavonoids are probably not involved in this process.

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Introduction Traditional healing is often the preferred form of therapy especially in rural and resource-limited communities. The extracts of plants are used to treat many diseases such as arthritis and chronic pain. Four medicinal plant species, namely, Acokanthera oppositifolia, Plantago lanceolata, Conyza canadensis and Artemisia vulgaris used in Southern Africa to treat pain and inflammation-related diseases were selected for evaluation in laboratory-based experiments. Methods The selected plant species were evaluated for phytochemical content, antioxidant and anti-inflammatory activities, as well as cytotoxicity effects against mammalian cells in culture. Results The results indicated that the n -hexane and chloroform extracts of P. lanceolata had the best antioxidant activities with an IC 50 =0.41 μg/mL. Also, the acetone extracts of P. lanceolata had 93.76% nitric oxide (NO) inhibition. However, the chloroform and n -hexane extracts of C. canadensis produced NO inhibition of 98.53% and 99.2%, respectively, at 100 μg/mL with IC 50 =17.69 μg/mL. Furthermore, the ethyl acetate extracts also had promising NO inhibitory activity (96.33%), but the cytotoxicity results with cell viabilities of 5.31%, 5.7% and 5.89%, respectively, suggested that the observed activity was due to a cytotoxic effect. Acetone extracts of C. canadensis were also cytotoxic at 30 µg/mL with 6.07–6.67% cell viabilities compared with the acetone extracts of P. lanceolata (99.57%). Conclusion The results partially validate the ethnomedicinal uses of the selected plant species used for inflammation-related conditions. However, because some of the extracts had potential cytotoxic effects, caution is advised in their use, especially those consumed orally.

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