Study of the antioxidant acitivity of rosemary (Rosmarinus Officinalis L.) extracts

Costa, D.; Costa, H.S.; Albuquerque, T.G.; Ramos, F.; Castilho, M.C.; Machado, A.V.; Sanches-Silva, A.

http://hdl.handle.net/10400.18/1942

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Background and objectives: Rosemary (Rosmarinus officinalis L.) is a rustic plant, from the mint family Lamiaceae. Rosemary extract has been recently approved as food additive (Directives 2010/67/EU and 2010/69/EU) and it has great antioxidant properties due to carnosic acid and carnosol in its composition, among other compounds (mainly phenolic acids, flavonoids, diterpenoids and triterpenes). In this study, rosemary was extracted with different solvents and analysed regarding its antioxidant activity (AA) using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging method. Methods: Rosemary was extracted with acetone, methanol, ethanol and hexane/ethanol. The AA of these extracts was studied and compared with those of standard compounds that are constituents of the rosemary extract (e.g. rosmarinic acid and carnosic acid) and with synthetic antioxidants used by the food industry (e.g. butylated hydroxytoluene). An aliquot of the antioxidant extract (50 μL) was added to 2 mL of DPPH radical methanolic solution (3.6 × 10-5 M), shaken vigorously and left to stand in the dark at room temperature. Absorbance was determined at 515 nm, after 16 min. Results and conclusions: The scavenging activity of the extracts was expressed as the % of inhibition of the DPPH radical. The EC50 value, representing the concentration of the extract that gives rise to 50% reduction in DPPH absorbance was determined by linear regression analysis. From the solvents used in this study, acetone was the solvent that originated the lowest EC50 and hexane/ethanol extract originated the highest EC50 and therefore, it has lower AA.