Phytochemical Extracts of Leucas aspera and Dahlia pinnata Exhibit Antimicrobial Properties in Escherichia coli and Enterococcus faecalis

Abstract

Phytochemicals such as tannins, alkaloids, flavonoids, and peptides have been found to have antimicrobial activity against a variety of bacterial strains. However, optimal extraction procedures for these phytochemicals and their efficacy evaluation against certain pathogenic bacterial strains remain unclear. Therefore, in this study, phytochemicals from Leucas aspera (L. aspera) and Dahlia pinnata (D. pinnata) were extracted by hot and cold extraction methods using water and methanol as solvents. In addition, antimicrobial activity of L. aspera and D. pinnata extracts against bacterial strains such as the gram-negative Escherichia coli (E. coli) and the gram-positive Enterococcus faecalis (E. faecalis) was performed by Minimal Inhibitory Concentration (MIC) and CFU quantification assays. The majority of the phytochemicals such as protein, carbohydrate, tannins, flavonoids, phenols, and saponins were present in our extracts, but steroids were absent in the extract. Protein, tannins, flavonoids, phenols, and saponins were present in both L. aspera and D. pinnata. The yield of proteins was high (1.990 ± 0.091 mg/ml) in methanol extracts of L. aspera and low (0.199 mg/ml) in aqueous extracts. However, the yield of tannins was high (1.713 ± 0.079 mg/ml) in methanol extracts of D. pinnata and low (0.528 ± 0.136 mg/ml) in aqueous extracts. The MIC of D. pinnata extracts were found to be 200 mg/ml for both E. coli and E. faecalis. However, the L. aspera extracts had an MIC of 100 mg/ml and 200 mg/ml on E. coli and E. faecalis, respectively. This article demonstrated the potential use of phytochemicals as novel antimicrobial compounds against bacterial infections.