Phytochemical profiling, evaluation of heavy metal load, antioxidant and antibacterial activity of various medicinal plants

In Ethiopia, medicinal herbs have played a prominent role in relieving pain and curing various diseases for humans and animals for many years. However, consumers don't know what kinds of phytochemicals are in the plants or the amount of metal they contain. Thus, in this study, polyphenol content, flavonoid content, antioxidant capacities, antibacterial activity and the level of metals in Asparagus africanus root, Ferula communis, Stephania abyssinia, Brucea antidysenterica and Vernonia amygdalina, were analyzed. Identifying the phytochemicals, antioxidant and antibacterial activities, and levels of metals in medicinal plants ensures their safety and efficacy and provides a deeper understanding of the healing properties of plants in areas where modern medicines are not easily accessible. The antioxidant activity was determined by 2,2-diphenyl- 1-picrylhydrazyl (DPPH) radical assay, and the antibacterial activity was evaluated by disc diffusion method. Among the studied plant extracts, Vernonia amygdalina displayed the maximum phenolic content (810 mg GAE/100 g), flavonoid content (515.78 mg QE/100 g), and DPPH radical scavenging activity (14.42 mg AAE/g), whereas the least level of total phenolic (160.82 mg GAE/100 g), total flavonoid (30.65 mg QE/100 g), and DPPH radical scavenging (1.14 mg AAE/g) were recorded in Asparagus africanus. The highest inhibition zone was recorded, with an inhibitory zone of 11 mm for S. aurous and 11 mm for E. coli. The least zone of inhibition was obtained in gram-negative bacteria (K. pneumonia) with a diameter less than 8 mm. Asparagus africanus contained the highest levels of Mn and Fe, while Cu and Zn were found to be the highest in Stephania abyssinia. Cr was only detected in Ferula communis, and Cd was found to be below the detection limit. Due to their better antioxidant and antibacterial properties, the extracts of these plants might be used as a natural starting material in treating cancer and to prepare anti-cancer drugs.