Identification of chemical compounds, antioxidant activity, total phenolic and flavonoid contents and cytotoxicity effect of Rosmarinus officinalis essential oil

Oxidative reactions are needed for human survival, but these reactions can sometimes be destructive. There is a lot of evidence that shows many disorders (neurological, renal, hepatic) and diseases such as cancer and vascular diseases, and even food spoilage are caused by oxidative reactions of free radicals. Some types of reactive oxygen species, such as oxygenated water, and free radicals such as hydroxyl and superoxide, can react with certain fats, nucleic acids, and proteins in the body to kill them. In general, any substance that delays or prevents the oxidation process is called an antioxidant. In various studies that have been done so far, the antioxidant and protective properties of the novel plants have been reported. Among other species of medicinal plants, the rosemary plant with the scientific name (Rosmarinus officinalis L.) belongs to the mint family, the leaves of which are used as an additive in many foods. This plant is cultivated in many parts of the world, including Iran, but the main habitat of this plant has been attributed to the shores of the Mediterranean Sea. The purpose of this study was to identify chemical compounds, antioxidant effects, total phenolic and flavonoids contents, and cytotoxicity effect of Rosmarinus officinalis essential oil (ROEO) on colorectal cancer cell line (HT29) and identification of functional groups of ROEO using Fourier transform infrared spectroscopy (FTIR). 

In the present study, the analysis of chemical compounds in ROEO was determined by gas chromatography-mass spectrometer (GC-MS). The total phenolic and flavonoid content of ROEO was evaluated using Folin-Ciocalteu and colorimetry using aluminum chloride, respectively. Antioxidant properties of ROEO were evaluated by DPPH and ABTS methods. The cytotoxic effect of ROEO on colorectal cancer cell lines (HT29) was evaluated by MTT method. The compositions of the functional groups present in the essential oil were investigated using Fourier transform infrared spectroscopy. 

The chemical analysis of ROEO comprised of 29 compounds, which composed 94.22% of total essential oil. The main compound identified in the essential oil used in this study was eucalyptol with 40.13%.  Total phenolic content was 72.55 mg gallic acid per gram of essential oil and its flavonoid content was 36 mg QE/g. The ROEO antioxidant activity for both DPPH and ABTS tests were 78.74% and 81.97%, respectively. The results of cytotoxic effect of ROEO showed that the cytotoxic effect of ROEO was highly dependent on its concentration. The higher the concentration of essential oil, the higher the level of cytotoxicity. Fourier transform infrared spectroscopy analysis confirmed the presence of aldehyde compounds, ketones, carboxylic acids, esters and alkenes. The results of all ROEO tests showed that this essential oil can be used as a potential source in the pharmaceutical, food, cosmetic and health industries.