Evaluation of Rhodiola crenulata and Rhodiola rosea for management of type II diabetes and hypertension.

In the current study, we investigated 2 species of the genus Rhodiola for the inhibition of alpha-amylase,alpha-glucosidase and angiotensin converting enzyme (ACE) inhibitory activity. Water extracts of Rhodiola crenulata had the highest alpha-amylase inhibitory activity (IC50,98.1 microg total phenolic /ml) followed by ethanol extract of R.crenulata (IC50, 120.9 microg total phenolic/ml) and ethanol extract of R.rosea (IC50, 173.4 microg total phenolic /ml). Ethanol R.rosea (IC50, 44.7 microg total phenolic/ml), water extract of R.rosea (IC50, 52.3 microg total phenolic/ml), water extract of R.crenulata (IC50, 60.3 microg total phenolic /ml) and ethanol extract of R.crenulata (IC50, 60.2 microg total phenolic/ml) also showed significant alpha-glucosidase inhibitory activity. The alpha-glucosidase inhibitory activity of the extracts was compared to standard tyrosol, which was significantly detected in the extracts using HPLC. Tyrosol had strong alpha-glucosidase inhibitory activity (IC50, 70.8 microg total phenolic/ml) but did not have any inhibitory effect on the alpha-amylase activity. Results suggested that alpha-glucosidase inhibitory activities of both Rhodiola extracts correlated to the phenolic content, antioxidant activity and phenolic profile of the extracts. The ability of the above Rhodiola extracts to inhibit rabbit lung angiotensin I-converting enzyme (ACE) was investigated. The ethanol extracts of R.rosea had the highest ACE inhibitory activity (38.5 %) followed by water extract of R.rosea (36.2 %) and R.crenulata (15.4 %).