Antimicrobial Activity, Cytotoxicity, and Qualitative Phytochemical Composition of Physalis Peruviana L. (Solanaceae) Leaf Extracts

Abstract

Microbial infections present a substantial worldwide health dilemma, particularly impacting susceptible populations. Despite the progress in medical science and the utilization of antibiotics, the eradication of pathogenic microorganisms proves arduous, with prevailing antimicrobial medications frequently yielding unfavourable outcomes. The imprudent application of antibiotics has engendered the emergence of resistant bacterial variants, have further complicated the therapy, and amplified healthcare expenses. Many medicinal plants, including Physalis peruviana L. (Solanaceae), lack rigorous scientific validation despite their potential antimicrobial agents, thus prompting this study. The antimicrobial activity of the two extracts was investigated using the disk diffusion technique against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Bacillus cereus, and Candida albicans according to the guidelines of the Clinical Laboratory Standards Institute (CLSI) to determine the growth inhibition zones. Moreover, the minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC) were determined according to a conventional procedure described by the CLSI. The cytotoxicity of the study extracts was determined using the brine shrimp lethality assay method to appraise their safety. Qualitative phytochemical analysis of the study extracts was performed using standard procedures to determine the presence of various phytochemicals. The results showed that the two extracts did not possess antimicrobial activity against P. aeruginosa and were either inactive or slightly inactive against the other microbes at a concentration of ≤ 50 μg/ml. It was observed that the aqueous extract had high to very high antibacterial activities against E. coli and S. aureus, and very high to remarkable activities against B. cereus. The methanolic extract showed remarkable antibacterial activity at concentrations of ≥200 μg/ml against E. coli, moderate to very high against S. aureus, high to very high against B. cereus, and moderate to high antifungal activity against C. albicans. The aqueous extract's minimum inhibitory concentrations (MICs) were 50 μg/ml (E. coli and B. cereus), 100 μg/ml (S. aureus), and 200 μg/ml (C. albicans). The minimum bactericidal concentration concentrations (MBCs) of the aqueous extract were 100 μg/ml (E. coli and B. cereus), 200 μg/ml (S. aureus), while the minimum fungicidal concentration (MFC) for C. albicans was 400 μg/ml. The MICs of the methanolic extract were 25 μg/ml for E. coli, S. aureus, and B. cereus and 100 μg/ml for C. albicans, and the MBCs were 100 μg/ml for E. coli, S. aureus, and B. cereus, and the MFC for C. albicans was 200 μg/ml. The aqueous extract was non-toxic, while the methanolic extract was slightly toxic to the brine shrimp nauplii, indicating their relative safety. Qualitative phytochemical screening of the two plant extracts revealed the presence of various phytochemicals, including alkaloids, saponins, tannins, glycosides, flavonoids, phenols, anthraquinones, cardiac glycosides, and coumarins; however, quinones and phytosterols were absent. These results indicate the studied plant extracts possess broad pharmacological activity, including, but not limited to antimicrobial activity. Therefore, the aqueous and methanolic leaf extracts of P. peruviana had varied antimicrobial activities against the tested microbes and may be potential sources of efficacious antimicrobials upon further investigations. Further studies aimed at identifying, isolating, and characterising the specific antimicrobial compounds from the studied extracts and determination of their specific mode(s) of action are recommended.