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.