Variations of peroxidase activity among Salvia species

Peroxidase was partially purified from Salvia species such as Salvia tomentosa Miller, Salvia virgata Jacq and Salvia viridis L. using solid (NH4)2SO4 precipitation and dialysis methods. We investigated the effect of some kinetic parameters such as buffer concentration, pH, temperature and substrate specificity on peroxidase activity. To clarify the role of peroxidase (POD) in enzymatic browning, oxidation of substrates such as 2,2′-azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid) (ABTS), o-dianisidine, o-phenylenediamine, catechol and guaiacol catalyzed by partially purified peroxidase was followed spectrophotometrically. POD was observed to oxidize some phenolic compounds in the presence of H2O2, leading to enzymatic browning. From the experimental results, we found that (i) POD activities varied with the buffer concentration as depending on the substrate studied, (ii) optimum pH values were 4.5, 2.5, 5.0, 7.0 and 6.0 for S. tomentosa Miller POD; 4.0, 2.5, 6.0, 6.0 and 7.0 for S. virgata Jacq POD; and 3.5, 2.5, 6.0, 7.0 and 7.0 for S. viridis L. POD using ABTS, o-phenylenediamine, o-dianisidine, catechol and guaiacol as substrates, respectively, (iii) optimum temperatures were 40, 30, 50, 50 and 50 °C for S. tomentosa Miller; those for S. virgata Jacq 60, 50, 60, 80 and 60 °C; and those for S. viridis L. 50, 50, 60, 20 and 50 °C using ABTS, o-phenylenediamine, o-dianisidine, catechol and guaiacol as substrates, respectively, and (iv) the substrate specificity of Salvia species was different from specie to specie and the best substrate for Salvia PODs was ABTS. Again, S. tomentosa Miller was the species with the highest POD activity, followed by S. virgata Jacq and S. viridis L. S. tomentosa Miller can be the most suitable Salvia species for dark-tea preparations because of the highest Vmax/Km values.