Temporal Profiling of Nutritional Phytochemicals and Stage-Specific Antioxidant Capacities in Rosa roxburghii Tratt ‘Guinong No. 5’ Fruit

Rosa roxburghii Tratt (RRT) is a native fruit in China, renowned for its high vitamin C (VC) content and rich bioactive compounds. To understand the changes in active substance content in RRT fruit and their contribution to antioxidant performance, we investigated total polyphenols, total flavonoids, total triterpenoids, ellagic acid, VC, superoxide dismutase (SOD), peroxidase (POD), glutathione (GSH), and malondialdehyde (MDA) during the development of RRT fruit ‘Guinong No. 5’. Antioxidant capacity was analyzed in vitro using DPPH, ABTS, and FRAP assays, and the correlation between these active substances and antioxidant capacity was compared. The results revealed that VC content increased continuously with fresh fruit development, reaching maximum at the maturity stage (S5) with 1922.67 mg/100 g. The contents of total polyphenols, total flavonoids, and total triterpenoids were generally similar, with young and mature fruits having relative higher levels. SOD activity was strongest at the green stage (S1) with 157.58 U/g. Correlation analysis showed that total polyphenol content was significantly positively correlated with DPPH (P < 0.01), and positively correlated with ABTS and FRAP (P < 0.05). Principal component analysis indicated the cumulative contribution rate of these active substances to the antioxidant capacity reached more than 80%. The results suggested the synergistic effect of these active substances played a decisive role in the antioxidant capacity of RRT fruits. These findings have significant theoretical and practical implications for understanding the composition and antioxidant capacity of active substances in RRT fruit.