Fruits from Rosa roxburghii: A Valuable Bioresource of Potent Radical Scavengers and Novel Ursane-Type Triterpenoids

Four new ursane-type triterpenoids named rosaroxine A-D and 21 known compounds were identified from Rosa roxburghii fruits. The structures of all compounds were established by 1D and 2D NMR spectroscopy and mass spectrometry. The phenolics catechin (EC₅₀ 13.4 μM), quercetin (13.1 μM), gallic acid (10.0 μM), and protocatechuic acid (15.2 μM) were identified as powerful in vitro antioxidants with EC₅₀ values lower than ascorbic acid (31.3 μM). The triterpenoids rosaroxine C (EC₅₀ 37.4; 40.3 μM) and 2-oxo-pomolic acid (16.6; 28.2) and the phenolics catechin (53.3; 29.0), quercetin (18.8; 33.1), and gallic acid (26.3; 40.0) exerted partly higher activities in the cyclo-oxygenase (COX 1/2) assay than the positive control acetaminophen (EC₅₀ 45.0; >100 μM). The triterpenoids rosaroxine C and 2-oxo-pomolic acid also performed well in the anti-aging assay using HaCaT cells. Quantification of the bioactive compounds by LC-MS revealed concentrations of 3.08 mg kg^-1 rosaroxine C, 17.40 mg kg^-1 2-oxo-pomolic acid, 76.29 mg kg^-1 catechin, and 5.58 mg kg^-1 protocatechuic acid in the dried fruits. Overall, this work provides detailed phytochemical information, and the results from the accomplished bioassay point toward health promoting properties of these fruits.