Screening of biological activities of extracts from Rhododendron mucronulatum Turcz. flowers

Extracts from Rododendron mucronulatum Turcz. flowers were tested for antioxidant and their inhibitory activities of a-amylase, a-glucosidase and angiotensin converting enzyme (ACE). Total contents of phenolics were found as 30.6±.14 mg/g (60% EtOH extract) and 23.2±0.21 mg/g (water extract). Electron donation ability (EDA), ABTS [2,2azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] radical decolorization, Antioxidant protection factor (PF) and thiobarbituric acid reactive substance (TBARs) were measured for the antioxidative activity of the extracts from Rododendron mucronulatum Turcz. flowers. The water extract were determined as 97.5% at ethanol extract showed 83.2% and 60% EtOH extract were 89.7% in EDA. The water extract showed higher antioxidant activity-than 60% EtOH extract when evaluated by ABTS radical decolorization and antioxidant PF. The TBARS of water extracts and 60% EtOH extracts were shown as 0.29 × 10², μM and 0.28 × 10² μM, respectively, and were lower than control. ACE inhibitory activity in water extract (67.6% inhibition) was higher than that of 60% EtOH extract (46.7% inhibition) at 200 μg/mL. Water extracts had higher inhibitory activities on a-amylase and a-glucosidase than 60% EtOH extracts. The result suggests that the water extract from Rododendron mucronulatum Turcz. flowers will be useful as natural antioxidants and functional foods.