There is very little scientific information on indigenous plants used for medicinal purposes. Therefore, the aim of the study was to evaluate the antibacterial and antioxidant activities of the leaves of Commelina africana, Elephantorrhiza elephantina, Dombeya rotundifolia, and the whole plant excluding the roots of Schkuhria pinnata indigenous medicinal plants from the Limpopo Province, which may be used for the treatment in humans infected with bacterial pathogens. The screening of different phytoconstituents using standard methods revealed the presence of terpenoids, flavonoids, tannins, and saponins. The total phenolic, tannin, and flavonoid content were estimated using spectrophotometric methods. D rotundifolia had the highest amounts of phenol (259.00 ± 2.65 mg of gallic acid equivalent [GAE]/g), tannin (330.33 ± 15.63 mg of GAE/g), and flavonoid (19.90 ± 0.75 mg of quercetin equivalent [QE]/g) content, while S pinnata had the least. All the plants had antibacterial activity against Escherichia coli and Pseudomonas aeruginosa with the bioautography method. The microbroth dilution assay revealed antibacterial activity with minimum inhibitory concentration values raining from 0.02 to 2.50 mg/mL. D rotundifolia had the highest antioxidant activity in both the free radical scavenging and ferric reducing power methods. S pinnata and C africana extracts had high antibacterial activity, while D rotundifolia had high antioxidant activity, which made them potential plants for isolation of bioactive compounds and possible application in the pharmaceutical industry.

BackgroundThe constant emergence of antibiotic resistant species and the adverse side effects of synthetic drugs are threatening the efficacy of the drugs that are currently in use. This study was aimed at investigating the possible antibacterial interactions, anti-inflammatory and cytotoxic effects of selected medicinal plants based on their traditional usage.MethodsThe acetone extracts of four plant species were assessed independently and in combination for antibacterial activity using microdilution assay and the sum of the fractional inhibitory concentration (FIC) was calculated. The ability of Dombeya rotundifolia and Schkuhria pinnata extracts to inhibit the production of reactive oxygen species (ROS) in LPS induced RAW 264.7 macrophage cells was evaluated using Dichloro-dihydro-fluorescein diacetate (H2DCF-DA) assay to determine anti-inflammatory potential and the toxicity on African green monkey kidney (Vero) cells was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay.ResultsThe antibacterial efficacies of the different combinations of Schkuhria pinnata (A), Commelina africana (B), Dombeya rotundifolia (C) and Elephantorrhiza elephantina (D) plants varied from combination to combination. Synergistic effects were only exhibited against P. aeruginosa, while the antagonistic effects were only observed against E. coli. Both S. pinnata and D. rotundifolia demonstrated anti-inflammatory potential by inhibiting the production of ROS in a dose dependant manner. The cytotoxicity of the plants (LC50 values) ranged from < 25.0 to 466.1 μg/mL. S pinnata extract was the most toxic with the lowest LC50 value of < 25.0 μg/mL.ConclusionsThe synergistic interaction observed indicates that combinational therapy may improve biological activity. This report highlights the anti-inflammatory potential of S. pinnata and D. rotundifolia; which could be exploited in the search for anti-inflammatory agents. However, the cytotoxicity of S. pinnata highlights the importance of using this plant with caution.

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