Total Phenolic Content and DPPH Free Radical Scavenging Activity of Young Turmeric Grown in Southern Thailand

摘要

Turmeric (Curcuma longa L.), a member of Zingiberacaeae, is used for Thai traditional medicine, flavoring, preservative, and coloring agent. In Southern Thailand, turmeric is a famous ingredient for food recipes. Not only is the ripened rhizome used for cuisine, but also the young rhizome. Previous studies have indicated that a variety of turmeric products from the ripened rhizome are valuable source of antioxidant compounds. However, there are ambiguous data regarding the level of antioxidant activity of the young rhizome. The aim of this study was to investigate the level of total phenolic content (TPC) and antioxidant activity of the young rhizome by comparing to the ripened rhizome. TPC and antioxidant activity of aqueous and 80% methanolic extracts from the young turmeric grown in Southern Thailand were estimated using the Folin-Ciocalteu method and DPPH free radical scavenging activity (DPPH-RSA) assay, respectively. Results showed that the concentration of TPC determined in methanolic extract (19.80±0.25 mg GAE/ g extract) from the young rhizome was significantly higher than the corresponding aqueous extract (18.38±0.41 mg GAE/ g extract). The aqueous and methanolic extracts exhibited significant inhibition in DPPH-RSA with the half-maximal inhibitory concentration (IC_(50)) value of 5.88± 0.70 mg/mL and 3.00±0.31 mg/mL, respectively. However, in comparison with the ripened rhizome, TPC and DPPH-RSA of the young rhizome were lower. These results indicated that the young rhizome grown in Southern Thailand could be a source of antioxidant compounds, but the ripened rhizome provides better antioxidant properties than the young rhizome.