Phytochemical Screening and Antibacterial Activity of different Two Varieties of Catharanthus roseus (L.) G. Don from South Africa

Abstract

Background and Aims: The rapid emergence of antimicrobial resistance (AMR) has created an urgent need for alternative antibacterial agents from natural sources. Catharanthus roseus is a medicinal plant rich in bioactive secondary metabolites with reported biological and pharmacological activities; however, comparative evaluation of its antibacterial efficacy across different leaf types remains limited. The present study aims to systematically evaluate the antimicrobial potential of methanolic extracts of C. roseus. Study Design:  Phytochemical screening and antibacterial activity evaluation of fresh and air-dried leaves samples of C. roseus (Pink and white floral varieties). Place and Duration of Study: Fresh plant materials of C. roseus were collected from University of Zululand, KwaDlangezwa campus, KwaDlangezwa, South Africa. Methodology: Methanol extracts of C. roseus leaves (pink and white varieties of fresh and dried leaves) were subjected to qualitative phytochemical screening using standard protocols. In vitro antibacterial activity of the extracts was assessed against Bacillus cereus (ATCC 10702), Staphylococcus aureus (ATCC 6538) and Enterococcus faecalis (ATCC 29212), Enterobacter cloacae (ATCC 13047), Escherichia coli (ATCC 4983), Kiebsiella pneumoniae (ATCC 2983), Pseudomonas aeruginosa (ATCC19582), Serratia marcescena (ATCC 9986), Acinetobacter calcaoceticus, Enterococcus faecailis, Micrococcus kristinae and Shigella flexineri using the disc diffusion and broth dilution methods, with gentamycin serving as positive control and reference antibiotic. Results: Phytochemical screening of the extracts revealed the consistent presence of alkaloids, flavonoids, glycosides, saponins, and terpenoids/steroids, while tannins and reducing sugars were absent. The extracts exhibited strong, broad-spectrum antibacterial activity, with zones of inhibition ranging from (8.3 ± 0.8 to 34.3 ± 1.4 mm). The highest activity was observed against Escherichia coli (34.3 ± 1.4 mm) and Staphylococcus aureus (30.7 ± 0.8 mm), with some extracts demonstrating comparable or superior effects to gentamycin. MIC and MBC values ranged between 0.3 to >10 µg/mL, and with low MBC/MIC ratios indicated predominantly bactericidal activity. Conclusion: Catharanthus roseus leaf extracts exhibit potent, broad-spectrum antibacterial activity. The strong inhibitory and bactericidal effects, particularly against relevant pathogens, highlight the potential of this plant as a promising source of novel antimicrobial agents.