We studied the total polyphenol content, DPPH radical scavenging activity, hydroxyl radical scavenging activity and α-glucosidase inhibition of water extracts from 17 medicinal plants. Total polyphenol contents ranged from 10.0 (Coix lachryma-jobi L, CL) ~ 279.7 (Perilla sikokiana, PS)mg/g. The water extract from medicinal plants were evaluated for its free radical scavenging activities and compared with a commercial antioxidant, ascorbic acid. DPPH radical scavenging activity of Pyrus pyrifolia (PP), Chamaecyparis obtusa L. (COL), Chamaecyparis obtusa F. (COF), and PS were higher than positive control. Higher hydroxyl radical scavenging activity were shown in Acanthopanax senticosus (AS) and Cordyceps militaris (CM) than the other plants. The highest anti-α-glucosidase activity was observed in Cornus officinalis (CO) and Paeonia suffruticosa Andrews (PSA) water extracts. PSA showed not only the higher DPPH radical scavenging activity but also the anti-α-glucosidase activity. The results of our study that PP, COL, COF, PS, AS, CM, CO and PSA could be potential candidates for natural antioxidants.

This study investigated the changes of antioxidant activity and α-glucosidase inhibitory effect of Jerusalem artichoke (Helianthus tuberosus) 100% methanol extracts by various heat treatment. The contents of total phenolic and flavonoid compounds in methanol extract tended to increased gradually with the rise of temperature to 180℃. The maximum yield of gallic acid (51.52 ± 2.17mg/g extract weight) and quercetin (13.39 ± 0.03mg/g extract weight) were obtained with extraction temperature of 180℃ for 120min. In addition, the improving extraction efficiency resulted in the increased biological activities, such as electronic donation ability (EDA, 90.36± 0.57%), reducing power (Abs 1.14) and α-glucosidase inhibitory effect (92.14 ± 1.14%). Overall, the results of this study indicate that the optimum conditions for the extraction process were an extraction temperature at 180℃ for 120 min, and will provide the basis for future research on the improving extraction yield of phenolic and flavonoid compounds.