Solvent extraction study of antioxidants from Balm (Melissa officinalis L.) leaves

In the paper, the extraction of antioxidants from Balm (Melissa officinalis L.) leaves with ethanol is presented. Effects of particle size, amount of solvent and temperature on the extraction rates and concentrations of antioxidants in the extracts were studied and kinetics was determined. Individual antioxidants (carnosic, ursolic and oleanolic acids) were identified by high performance liquid chromatography. Results showed that the intraparticle diffusion was the rate-governing step of the extraction process. The extractions all proceeded in three stages: an initial washing stage, a fast stage and a slower stage. Experimental extraction curves were analysed with a mathematical model derived from Fickʹs second law, and diffusion coefficients of the antioxidants within the particles under different operating conditions in ethanol were determined.