EVALUATION OF ANTIOXIDANT AND ANTIMICROBIAL EFFICACY OF COLEUS BARBATUS AGAINST DRUG-RESISTANT MICROORGANISMS IN NORTH BIHAR

Nuzhat Parween*, Rima Kumari, Mustafa Kamal Ansari

Background: The emergence of drug-resistant microorganisms poses a significant public health challenge globally, particularly in resource-limited settings such as North Bihar, India. Coleus barbatus (Andrews) Bent. ex G. Don (Syn. Plectranthus barbatus, Coleus forskohlii), a medicinal plant of the Lamiaceae family, has been traditionally used for various ailments but lacks systematic evaluation against clinically relevant drug-resistant strains from this geographic region. Methods: Coleus barbatus roots and leaves were collected from Muzaffarpur district, North Bihar. Sequential extraction was performed using hexane, ethyl acetate, ethanol, and aqueous solvents. Phytochemical screening quantified total phenolic (TPC) and flavonoid (TFC) contents. Antioxidant activity was evaluated using DPPH•, ABTS•⁺, and FRAP assays. Antimicrobial efficacy was assessed against clinical isolates of MRSA, E. coli (ESBL-producing), P. aeruginosa, and Candida albicans using disc diffusion and broth microdilution methods (CLSI guidelines). For comparative standardisation, forskolin content was quantified via HPLC. Results: The ethanolic extract demonstrated the highest TPC (156.4 ± 3.2 mg GAE/g) and TFC (89.7 ± 2.1 mg QE/g). Antioxidant assays revealed IC₅₀ values of 32.6 ± 1.8 μg/mL (DPPH•) and 28.4 ± 1.5 μg/mL (ABTS•⁺), comparable to ascorbic acid. The ethyl acetate extract exhibited potent antibacterial activity against MRSA (MIC: 64 μg/mL; zone of inhibition: 18.3 ± 0.6 mm) and ESBL-producing E. coli (MIC: 128 μg/mL; zone: 15.7 ± 0.4 mm). Biofilm inhibition assays demonstrated significant disruption of P. aeruginosa PAO1 biofilm formation (68.4% inhibition at 2× MIC). HPLC quantification confirmed forskolin content of 0.42% (root) and 0.18% (leaf). Conclusion: Coleus barbatus from North Bihar exhibits significant antioxidant and antimicrobial activity against drug-resistant pathogens, with biofilm inhibition suggesting quorum sensing modulation as a potential mechanism. These findings support its ethnopharmacological relevance and warrant further investigation for lead compound identification.