Abstract

The aim of this study is to evaluate the biological activities of some plant species used in the preparation of herbal mixtures and determine the combinational effects. The plant materials were collected from traders who use them to prepare herbal mixtures claimed to be blood purifiers, pain-relievers, anti-diarrheal and aphrodisiac medicines. An aqueous decoction of each plant species was prepared. Thin layer chromatography (TLC) was used to establish the phytochemical profiles of the decoctions. Standard chemical tests were performed to screen for the presence of phyto-constituent groups. Total polyphenol content of the decoctions was also determined. The 2, 2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay and ferric reducing power were used to assess the antioxidant activities of the extracts. The micro-broth dilution assay was used to determine antimicrobial activity. Fractional inhibitory index was used to determine the consequence of mixing different decoctions together.  The phytochemical fingerprints of the decoctions showed that water mainly extracted polar compounds from the plants. Terpernoids, tannins and steroids were detected in all the decoctions. The decoctions of Delonix elata, Veltheimia capensis, Sarcostemma viminale, and “Tšhikwana” had the lowest antioxidant activity. The twigs of Kirkia wilmsii exhibited the greatest antioxidant activity (EC50 15.71 µg/mL) and further showed significant broad-spectrum antibacterial activity against diarrheagenic pathogens. The twigs of K. wilmsii had the greatest amount of total phenolics followed by Hypoxis hemerocallidea (corm) and Monsonia angustifolia. Majority of the aqueous extract combinations yielded indifferent and additive interactions. Although synergistic effects are sought after when mixing different plant extracts, this study demonstrated the complexities associated with combinations of aqueous extracts and the importance of appropriate knowledge on which species of plants should be mixed to enhance their therapeutic properties.

Key words: Phytochemical screening, antioxidant, antimicrobial, combinational effects.