Phytochemical screening and antimicrobial activity of stem extract of Coleus forskohlii L. collected from Al-Baha Area, Saudi Arabia

This study aimed to investigate the phytochemical screening, total phenolic content, antioxidant and antimicrobial activities of Coleus forskohlii L. stem extract in Al-Baha area, Saudi Arabia. Stem samples were collected from Al-Baha area and air-dried followed by extraction with ethanol, petroleum ether, chloroform, ethyl acetate, and n-butanol. The extracts were then subjected to phytochemical screening, determination of total phenolic content, antioxidant and antimicrobial activities. Results showed the presence of flavonoids, alkaloids, tannins, terpenoids, steroids, saponins, and reducing sugars. Total phenolic content was significantly (P<0.001) higher in n-butanol extract (274.33±3.29 mg GAE/gm), followed by ethyl acetate extract (182.94±1.82 mg GAE/gm), ethanol extract (79.63±2.02 mg GAE/gm) and petroleum ether extract (73.38±3.07 mg GAE/gm), while the lowest content was in chloroform extract (60.06±2.12 mg GAE/gm). The antioxidant activity was significantly (P<0.001) higher in n-butanol extract (67.68±1.55%), followed by ethyl acetate extract (43.38±1.27%), ethanol extract (36.02±1.29%), petroleum ether extract (20.71±0.59%) and chloroform extract (19.73±0.74%). The antimicrobial activity showed that all microorganisms tested were resistant at the concentration of 25 and 50 mg/ml of plant extracts, whereas the concentrations of 100, 150 and 200 mg/ml showed varying activities against gram-negative (Escherichia coli, Pseudomonas aeruginosa), gram-positive (Staphylococcus aureus, Bacillus cereus) and Candida albicans. The study concluded that the stem extracts of C. forskohlli have promising pharmacological and biological activities that could be beneficial in pharmaceutical as well as food and medicinal industries.