Phytochemical Screening, Chemical Composition, Antimicrobial Activity and in Silico Investigation of the Essential Oil of Coleus forskohlii L. Collected from the Southwestern Region of Saudi Arabia

Abstract

This study aimed to investigate the phytochemical constituents, chemical composition, and antimicrobial activity of the essential oil isolated from the leaves of C. forskohlii plants and performed theoretical in silico calculations for selected chemical components identified in the obtained essential oil. The collected C. forskohlii leaves were air-dried and treated with ethanol, chloroform, ethyl acetate, n-butanol, and petroleum ether. The extracted essential oil was subjected to GC/MS analysis to determine its chemical composition and was screened in vitro for antimicrobial activity against gram-positive and gram-negative bacteria, and Candida albicans fungus strains. Phytochemical analysis revealed the presence of flavonoids, alkaloids, tannins, terpenoids, steroids, saponins, and sugars. Twenty-five compounds were identified with thymol (52.02 %), γ-terpinene (18.70 %) and o-cymene (12.73 %), as the major components. 2-Undecanone (2.57 %), 6-methyl-2-heptanol, acetate (1.50 %), (+) -4-carene (1.47 %) and caryophyllene oxide (1.36 %) were detected in small quantities. The essential oil showed a significant effect against the bacterial and fungal strains with inhibition zones in the range of 19-20.33 mm (p<0.001). The results indicated that the essential oil extracted from C. forskohlii leaves is rich in phytochemical constituents of pharmaceutical importance as a broad-spectrum antimicrobial agent. Moreover, the in silico pharmacokinetic study indicated that some of the selected molecules had high GI absorption and all molecules examined in the screening processes showed good bioavailability with a score of 0.55. Additionally, the results suggest a more favorable drug-likeness of the examined selected molecules.