Flavonoids from the Buds of Rosa damascena Inhibit the Activity of 3-Hydroxy-3-methylglutaryl-coenzyme A Reductase and Angiotensin I-Converting Enzyme

Rosa damascena has been manufactured as various food products, including tea, in Korea. A new flavonoid glycoside, kaempferol-3-O-β-d-glucopyranosyl(1→4)-β-d-xylopyranoside, named roxyloside A was isolated from the buds of this plant, along with four known compounds, isoquercitrin, afzelin, cyanidin-3-O-β-glucoside, and quercetin gentiobioside. The chemical structures of these compounds were determined by spectroscopic analyses, including FAB-MS, UV, IR, 1H and 13C NMR, DEPT, and 2D NMR (COSY, HSQC, and HMBC). All the isolated compounds except cyanidin-3-O-β-glucoside exhibited high levels of inhibitory activity against 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase with IC50 values ranging from 47.1 to 80.6 μM. Cyanidin-3-O-β-glucoside significantly suppressed angiotensin I-converting enzyme (ACE) activity, with an IC50 value of 138.8 μM, while the other four compounds were ineffective. These results indicate that R. damascena and its flavonoids may be effective to improve the cardiovascular system.