In-vitro inhibitory effects of flavonoids in Rosa roxburghii and R. sterilis fruits on α-glucosidase: Effect of stomach digestion on flavonoids alone and in combination with acarbose

Inhibitory effects (IEs) of flavonoids from Rosa roxburghii and R. sterilis fruits against α-glucosidase were investigated. Crude extract of R. roxburghii fruits (RrCE) and R. sterilis fruits (RsCE) were extracted with ethanol. The n-butanol extraction of aqueous RrCE dispersion (RrCE-B) showed the greatest inhibition of α-glucosidase. The most abundant three components in RrCE-B were kaempferol hexose, rutin, and catechin (Cat). The predominant active compounds were characterized as flavonoids by UV–vis spectra. Combination analysis suggested that RrCE was a favorable choice to combine with acarbose (Aca). After simulated gastric digestion, IEs of flavonoids decreased greatly, especially when sodium nitrite was supplemented in the simulated gastric fluid (SGF). The UV–vis spectra indicated that flavonoids were basically stable in the SGF without sodium nitrite, but were oxidized by the HNO2, a natural component in the gastric fluid. The results of this study will help food scientists design special foods for diabetic patients.