GC‐MS Based Metabolite Profiling, Antioxidant and Antimicrobial Properties of Different Solvent Extracts of Malaysian <i>Plectranthus amboinicus</i> Leaves

Abstract

This study evaluates the phytochemistry, antioxidant, and antimicrobial effects of <i>Plectranthus amboinicus</i> leaves extracted in different solvents. The methanol extract contained the highest total phenolic (94.37 ± 1.24 mg GAE/g) and flavonoid contents (26.90 ± 1.35 mg RE/g) and exhibited the highest DPPH scavenging activity (90.13 ± 3.32%) followed by the acetone extract (80.23 ± 3.26%) at 500 <i>μ</i>g/mL concentration. Similarly, the highest ferric ion reduction potential (849.63 ± 30.95 <i>μ</i>M of Fe (II)/g dry weight) was exhibited by the methanol extract followed by the acetone extract (695.92 ± 25.44 <i>μ</i>M of Fe (II)/g dry weight). The methanol extract showed greater antimicrobial activity against all the tested pathogens (<i>Bacillus subtilis</i>, Methicillin-resistant <i>Staphylococcus aureus</i>, <i>Pseudomonas aeruginosa</i>, <i>Escherichia coli</i>, and <i>Candida albicans</i>). However, both hexane and acetone extracts failed to inhibit <i>E. coli</i>. <i>S. aureus</i> and <i>C. albicans</i> were more susceptible to all the extracts. Further, GC-MS analysis confirmed the occurrence of a total 46 phytocompounds in different solvent extracts. Some of the major compounds included carvacrol (37.7%), tetracontane (16.6%), squalene (15.6%), tetrapentacontane (13.7%), and Phytol (12.9%). In conclusion, extraction solvents influenced the recovery of phytocompounds and the highest pharmacological activities of the methanol extract could be correlated to the presence of additional bioactive compounds.