Qualitative Determination of the Secondary Metabolites and Evaluation of the Antimicrobial Activity of Leaf Extracts from Different Plant Families (Boraginaceae, Fabaceae, Lamiaceae and Lauraceae) against Microorganisms of Clinical Importance

Aims: This study was conducted to investigate the antimicrobial activities of Sassafras albidum (Nutt.), Ehretia anacua (Terán & Berl.), Melissa officinalis (Linn.), Eysenhardtia texana (Scheele), and Melissa odorata. Specifically, this study aims to evaluate the antimicrobial potential and to qualitatively determine presence of secondary metabolites in the different leaf extracts.

Place and Duration of Study: Plant leaves were collected from the San Antonio Botanical Garden in Texas. The microbial assays and chemical analysis were done at the Department of Biology and Chemistry, Texas A&M International University, Laredo Texas. This study was done from October 2013 to May 2016.

Methodology: Leaves were collected and aqueous, acetone, diethyl ether, and ethanol leaf extracts were prepared. Antimicrobial activity against bacteria and fungi were investigated via disc diffusion assay. Phytochemical screening was done to qualitatively determine secondary metabolites.

Results and Conclusion: The ethanol and diethyl E. anacua (Boraginaceae) extracts showed a statistically significant antimicrobial activity against S. aureus. Although the values, 7.4 mm and 7.5 mm for the ethanol and diethyl ether extracts could be low values for zone of inhibitions, the potential for E. anacua for anti-S. aureus activity cannot be undermined. Phytochemical analysis showed detectable presence of alkaloids, diterpenes, and phenols in the ethanol and diethyl E. anacua extracts. Results of this study, although preliminary, demonstrated the potential of E. anacua as a new source of bioactive metabolites. Further investigations are needed in order to specifically identify, quantify, and isolate the bioactive compounds that might act against S. aureus associated skin infections.