EFFECT OF FAR-INFRARED IRRADIATION ON THE ANTIOXIDANT ACTIVITY OF PUERARIAE RADIX EXTRACT

Abstract

ABSTRACT The effect of far-infrared (FIR) irradiation on the antioxidant activity of Puerariae radix (PR) extracts was evaluated. PR was placed in pyrex petri dishes (8.0 cm diameter) and irradiated at 90, 100 and 110C for 0, 10, 20, 30, or 40 min using a FIR heater. After treatment, methanol extracts of PR were prepared and total phenolic contents (TPC), radical scavenging activity (RSA) and reducing power (RP) of the extracts were determined. FIR irradiation increased the antioxidant activities of the PR extracts. When PR was FIR irradiated at 110C for 40 min, the values of TPC, RSA, RP and puerarin content of its methanolic extract were increased from 0.096 to 0.148 g/mL, 80.79 to 84.05%, 0.999 to 1.360 and 66.0 to 77.8 ppm, respectively, compared to that of nonirradiated PR. The results indicated that appropriate FIR irradiation of PR could increase the antioxidant activities of methanolic extracts. PRACTICAL APPLICATIONS Puerariae radix (PR) has been widely used in eastern Asia to treat the common cold, influenza, and wrist and shoulder stiffness and as an antidipsotropic agent. In this article, we report that appropriate far-infrared (FIR) irradiation can increase the antioxidant activity of PR. For example, when PR was FIR irradiated at 110C for 40 min, the values of total phenol contents, radical scavenging activity, reducing power and puerarin content of its methanolic extract were increased from 0.096 to 0.148 g/mL, from 80.79 to 84.05%, from 0.999 to 1.360 and from 66.0 to 77.8 ppm, respectively, compared to that of nonirradiated PR. The results indicated that appropriate FIR irradiation could be applied to increase the quality of PR.