SALVIA LERIIFOLIA بررسي مقاومت حرارتي فراكسيون عمده آنتي اكسيداني برگ گياه نوروزك

Investigation of heat stability of major antioxidant fraction of salvia leriifolia leaves

Heat stability or carry-through properties of major antioxidant fraction of Salvia leriijblia leaves in comparison with BHT and a-tocopherol was investigated by using of Rancimat method at 90, 120 and 180°C, and active oxygen method (AOM). Carry-through properties are defined as the antioxidant resistance against thermal decomposition and evaporation or steam distillation. Descending order of antioxidant activity based on the methods of AOM and Rancimat. at 90°C were BHT, Salvia antioxidant and a-tocopherol. Activity of the Salvia antioxidant and BHT at 120°C had no significant difference, and acted different from a-tocopherol. a-tocopherol showed the highest antioxidant activity at 180°C in comparison with Salvia and BHT which had no significant difference with control. Induction period of oil sample in presence of different antioxidants was drawn against temperature, and two quantities of standard coefficient and induction period at 20°C (t20) were calculated from fitted curve. The t20 of the antioxidants were divided by t20 of control separately to achieve a quantity named protection factor at 20°C (Pf2o). Standard coefficient and Pf20 were used for showing the carry-through properties and activity of different antioxidants, respectively. The highest Pf20 was for BHT and then Salvia antioxidant and a-tocopherol, respectively (1.27, 1.19 and 1.01). Descending order of carry-through properties was a-tocopherol, Salvia antioxidant and BHT (Pf70 of 0.5229, 0.5216 and 0.5202, respectively).