Pharmacological evaluation of two South African commercial herbal remedies and their plant constituents

Amandla impilo immune booster and sejeso are two widely used South African commercial herbal remedies that are prepared from a mixture of several plants. They are used as multipurpose treatments for curing various diseases and ailments including gastrointestinal disorders, and diabetes (amandla impilo). This study was aimed at determining the pharmacological potential of the two herbal remedies, and eleven constituent plant species used in their preparation. Water and 70% aqueous acetone were used for extraction, and 30 extracts in total were evaluated for antibacterial activity against Campylobacter jejuni, Escherichia coli, Shigella flexneri and Staphylococcus aureus from the American Type Culture Collection. Extracts that exhibited antibacterial activity with minimum inhibitory concentration (MIC) values less than 1 mg/ml against at least three bacterial strains were evaluated for cytotoxicity against monkey kidney (Vero) cells. Amandla impilo immune booster and its plant constituents were evaluated for antidiabetic potential against the alpha-glucosidase enzyme. The MIC values ranged from 0.195-12.50 mg/ml, and the best value was demonstrated by 70% aqueous acetone extracts of Elephantorrhiza burkei roots against S. aureus and S. flexneri as well as Peltophorum africanum bark and leaves against S. flexneri (MIC = 0.195 mg/ml). The 70% aqueous acetone leaf extracts of Gunnera perpensa and P. africanum, as well as the water extract of Hypoxis obtusa corms were not toxic to Vero cells. However, 70% aqueous acetone extracts of E. burkei roots, H. obtusa corms and P. africanum bark showed slight toxicity towards the cells, and thus should be administered cautiously. Amandla impilo immune booster exhibited stronger alpha-glucosidase inhibitory activity (40.08 μg/ml) than the positive control, acarbose (1040.00 μg/ml), providing credence for the antidiabetic use of this concoction. Interestingly, water extracts of G. perpensa leaves and rhizomes (2.61 and 2.72 μg/ml respectively), 70% acetone extracts of G. perpensa leaves (5.69 μg/ml), Watsonia densiflora bulbs (9.08 μg/ml), Combretum krausii bark and leaves (19.38 μg/ml), G. perpensa rhizomes (18.00 μg/ml), W. densiflora bulbs (14.82 μg/ml) and Mimusops obovata bark (17.25 μg/ml) showed stronger inhibition of the enzyme, demonstrating more antidiabetic potential individually than the commercial mixture they make. In conclusion, the observed antibacterial and antidiabetic activity of some plants, if supported by further studies, might justify their inclusion in the makeup of the tested herbal remedies. Although amandla impilo and sejeso showed low antibacterial activity, more research determining potential toxicity and antibacterial activity against bacterial strains, not tested in this study, is required as these two concoctions are used in traditional medicine practice against various diseases. This study confirmed the antidiabetic potential of amandla impilo, therefore, further studies on its antidiabetic activity and possible synergistic potential due to mixing of plant extracts are required.