Evaluation of total phenolic content and antioxidant activity of different Rosmarinus officinalis L. ethanolic extracts

Botanical extracts are one of the richest sources of antioxidants that counteract both free radicals and oxygen reactive species. The solvent and extraction conditions used in the extraction may influence the quantity, antioxidant composition and biological activity. Ethanolic extracts of rosemary leaf were produced by maceration and percolation and different ethanol concentrations (30, 40, 50, 60, 70, 80, 90 and 96%) were used for extraction. Influence of ethanol concentration and extraction method on the amount of total phenolic content and antioxidant activity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical inactivation were determined spectrophotometrically. The most potent solvent concentration was 50% for the evaluation of total polyphenols 47.39 ± 0.21 mg/mL RAE. All tested rosemary extracts showed high DPPH radical inactivation which ranged from 75.96 ± 1.12% to 85.81 ± 0.14%, but no statistically significant difference (P > 0.0624) was observed. The dry residue was also evaluated and it was higher in the liquid extracts than in tinctures. Stirring of rosemary leaves increased the total phenolics (from 42 till 53 mg/ml RAE) in the 50% ethanolic rosemary tincture. Extraction by percolation showed higher amounts of dry residue and phenolics, but antioxidant activity was lower. Correlation between the total phenolic content and antioxidant activity was not observed. Active moistening is effective and can increase the amount of extractive substances from herbal materials.