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 alpha-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 alpha-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.