Antimicrobial Activity against Antibiotic-resistant Pathogens and Antioxidant Activity and LCMS/MS Phytochemical Content Analysis of Selected Medicinal Plants

Abstract

Medicinal plants are a major source of numerous therapeutic agents, and the emergence of pathogenic bacteria has rekindled interest in traditional medicine systems as an alternative approach to overcoming resistance. The dried plant material of four medicinal plants, namely Terminalia arjuna (bark), Terminalia bellirica (fruit), Aegle marmelos (leaves), and Bacopa monnieri (leaves), was powdered, and aqueous extracts were prepared. The antimicrobial activity of the extracts was evaluated against three clinically important strains: Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli 385. As E. coli 385 was resistant to the broadest spectrum of antibiotics tested, it was classified as (MDR multi-drug resistant). E. coli, Bacillus subtilis, Mycobacterium smegmatis (MTTC), and Vibrio alginolyticus (ATCC) were also assessed using the agar well diffusion method for zones of inhibition and minimum inhibitory/bactericidal concentration (MIC/MBC). Clinically important strains were found to be sensitive to the aqueous extract of T. bellerica (19.51 ± 0.61 mm) with MICs ranging from 0.31 to 0.62 mg/ml. The MDR strain was also sensitive to Bellirica monnieri (16.10 ± 0.31 mm) aqueous extract. To determine the potential for a wide range of applications, the antioxidant activities of the extracts were evaluated using DPPH, ABTS, and FRAP assays. The T. arjuna plant extract exhibited the highest radical scavenging activity with the lowest EC50 values for DPPH (1.15 ± 0.061 mg/ml) and ABTS (1.02 ± 0.07 mg/ml). The plant extracts were characterized by UV-visible spectroscopy, Fourier-transform infrared spectroscopy, and LC-MS/MS.