Phytochemical analysis and evaluation of antimicrobial, anti-inflammatory, antioxidant, and cytotoxic properties of Berkheya onopordifolia

Introduction: Berkheya onopordifolia and other Berkheya species are used traditionally to treat fever, malaria, skin conditions, sexually transmitted infections, gastrointestinal issues, and inflammation in many regions of Southern Africa. This study aimed to validate its traditional uses through in vitro analysis of methanol, acetone, and aqueous extracts for antimicrobial, anti-inflammatory, antioxidant, and cytotoxic properties. Methods: The nitric oxide (NO) assay was used to evaluate anti-inflammatory activity, while cytotoxicity was determined using Hoechst 33342/PI staining method. Antioxidant activity was assessed through 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Ferric ions reducing antioxidant power (FRAP) assays, and antimicrobial activity using the broth microdilution technique. Bioactive compounds were examined using different qualitative and quantitative techniques. Results: Flavonoids, alkaloids, steroids, glycosides, diterpenes, and dicarboxylic acids were identified in the extracts. Antimicrobial activity was observed in both methanol and acetone extracts, at minimum inhibitory concentrations (MICs) between 0.6 to 1.25 mg/mL against Candida albicans, Candida parapsilosis, and several gram-negative and positive bacteria, including Escherichia coli, Neisseria gonorrhoeae, Staphylococcus aureus, and Streptococcus pneumoniae. Acetone extracts inhibited NO release by over 50%, indicating strong anti-inflammatory potential, but showed cytotoxicity to Vero cells at 400 µg/mL. It also exhibited moderate antioxidant activity (IC₅₀ = 9.83 ± 0.31 µg/mL), significantly different (P≤0.001) from Trolox (6.17±0.43 µg/mL) and ascorbic acid (6.57±0.98 µg/mL). Conclusion: Despite low selectivity and linear correlation values, the acetone extract demonstrated notable antimicrobial, anti-inflammatory, and antioxidant activities. These findings support the traditional medicinal use of B. onopordifolia and highlight the need for further studies on its isolated bioactive compounds.