夏枯草水解寡糖组分的分离、结构解析与体外抗氧化及肠道菌群丰富度调节作用OA

Objective To isolate structurally defined bioactive oligosaccharide fractions from Prunella vulgaris(PV)polysaccharides and evaluate their in vitro antioxidant activity and intestinal microbiota-modulating effects.Methods Total polysaccharides were extracted via water extraction and alcohol precipitation,followed by deproteinization using the Sevag method.Partial acid hydrolysis was performed under two conditions(80 ℃ and 100 ℃,0.5 mol/L trifluoroacetic acid).The hydrolysates were fractionated and purified by hydrophilic interaction chromatography(HILIC).Structural characterization of the dominant components in each fraction was performed using HILIC/IM-QTOF-HDMSE,UHPLC-UV and 1D/2D-NMR(1H/13C-NMR,COSY,HSQC,HMBC).Antioxidant activity of three oligosaccharide components was assessed via a DPPH free radical scavenging assay,while their modulatory effects on gut microbial abundance were evaluated using an in vitro anaerobic co-culture model of mouse fecal microbiota coupled with real-time quantitative PCR.Results Three oligosaccharide fractions with degrees of polymerization(DP)of 2,3,and 5 were obtained,namely DP2(yield:5.60％),DP3(1.19％),and DP5(1.70％).The dominant structural features of three fractions were elucidated as follows:DP2 is mainly composed of a disaccharide composed of 3-O-methyl-α-glucuronic acid linked to xylose,with α/β anomerism at the xylose terminus;DP3 mainly contains a trisaccharide consisting of xylose-arabinose-uronic acid,terminating in either 4-O-methyl-β-glucuronic acid or α-galacturonic acid;DP5 is primarily a linear pentasaccharide starting with 2-O-methyl-α-glucuronic acid,linked through three xylose units,and ending with 3-O-methyl-glucuronic acid existing in both α-and β-forms.Antioxidant assessment revealed that all three fractions exhibited significant DPPH radical-scavenging activity,with DP5 being the most potent(IC50=0.36μg/mL).At 0.1 mg/mL,both DP3 and DP5 showed scavenging rates exceeding 84％,comparable to the positive control VC(IC50=0.11 μg/mL,P＞0.05).Microbiota analysis indicated that all three fractions modulated the intestinal flora:DP2 significantly promoted the growth of the probiotic genus Lactobacillus;DP3 increased the abundance of the beneficial phylum Bacteroidetes while suppressing the potentially pathogenic phylum Actinobacteria;DP5 primarily exerted inhibitory effects on Actinobacteria.Conclusion This study successfully isolated three oligosaccharide fractions(DP2,DP3,and DP5)from the PV polysaccharides and characterized their predominant structural features,revealing the antioxidant and gut microbiota-regulating activities.