Phytochemical Screening and in Vitro Antimicrobial and Anticancer Activities of Different Extracts of Rosmarinus officinalis (Rosemary): A Comparative Study

Various medicinal plants are found in the dense forest of Albaha region, southwest of Saudi Arabia. These plant species are natively utilized for the prevention and treatment of various diseases. This study was designed to analyze the chemical composition of ethanolic, petroleum ether, chloroform, and methanolic extracts of Rosmarinus officinalis (rosemary) collected from Albaha region and evaluate the antimicrobial and cytotoxic activities of these extracts. Fresh aerial parts of R. officinalis (stem and leaves) were used for extraction. Then the crude extracts were investigated by using gas chromatography- mass spectrometry (GC-MS) technique to determine their chemical constituents. Antimicrobial assays were performed using Bacillus subtilis and Staphylococcus aureus (Gram-positive bacteria), Escherichia coli (Gram-negative bacteria), and Candida albicans (fungus) to determine the antimicrobial activities. MTT assay was applied to MCF-7 (human breast cancer cell line) as well as on HCT-116 (human colon cancer cell line) to calculate the IC50 of different plant extracts. The GC-MS analysis showed that only petroleum ether extract has an abundance of cyclohexane compounds including 46.5% methyl-cyclohexane. Significant antibacterial and antifungal actions against the tested strains were shown by the petroleum ether and chloroform extracts in antimicrobial assay. Antibacterial activity against S. aureus (SA) and E. coli (EC) was exhibited by methanolic extract, whereas no effect was observed on B. subtilis (BS) and C. albicans (CA). In MTT assay, the petroleum ether extract showed the greatest cytotoxic activity against MCF-7 (3.77 μg/mL) and HCT-116 (3.09 μg/mL) cells. The extract of chloroform also displayed significant cytotoxic effect but only against MCF-7 with IC50 values of 12.7 µg/mL. The present study showed that the R. officinalis petroleum ether extract contains significant antimicrobial and cytotoxic activities which can be accredited to the plentiful manifestation of methyl-cyclohexane, methylbenzene and other cyclohexane derivatives, and it may be used to develop new antimicrobial and anticancer drugs.