Evaluation of the in vitro Antibacterial and Antioxidant Activities, Cytotoxic Effects, and Phytochemical Screening of Root Extracts of Kedrostis capensis A. Meeuse and Trachyandra asperata Kunth. from Lesotho

Abstract

The high mortality rate due to infectious diseases has recently been associated with the development
of resistance to antibiotics by several strains of microorganisms worldwide. One of the pathophysiological
conditions of mammalian tissues in response to infectious organisms is oxidative stress. Natural extracts or their
chemical constituents as antioxidants are known to be very effective at preventing the destructive processes
caused by oxidative stress. The main aim of the current study was to evaluate in vitro antibacterial, antioxidant,
and cytotoxic effects of ethanolic root extracts of Kedrostis capensis A. Meeuse (Cucurbitaceae) and Trachyandra
asperata Kunth. (Xanthorrhoeaceae). Materials and Methods: The assessments of antibacterial and antioxidant
effects were performed using well diffusion method and 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical
scavenging activity assay, respectively, while cytotoxic potentials were evaluated by employing the brine
shrimp toxicity model. Results: K. capensis extract possessed bactericidal activity against Escherichia coli and
Staphylococcus aureus and bacteriostatic activity against Pseudomonas aeruginosa with minimum inhibition
concentration (MIC) values ranging from 62.5 to 500 μm/mL and minimum bactericidal concentration (MBC)
values varying from 125 to 1000 μm/mL, while T. asperata extract was only bacteriostatic against S. aureus
with MIC value of 500 μm/mL and MBC value greater than 1000 μm/mL. Both K. capensis and T. asperata
extracts scavenged DPPH free radicals in a concentration-dependent manner with the half maximal inhibitory
concentration (IC50) values of 113.68 ± 0.11 μg/mL and 134.63 ± 0.27 μg/mL, respectively. K. capensis extract
exhibited a relatively higher toxicity potential with 50% lethality concentration (LC50) value of 102.37 ±
0.19 μg/mL, while T. asperata was non-toxic with lower LC50 value of 522.75 ± 0.35 μg/mL. Obtained results
suggest that K. capensis and T. asperata ethanolic root extracts possess bioactive secondary metabolites with
antibacterial, antioxidant, and cytotoxicity properties with potential pharmaceutical applications.