Analysis of Nutrient Composition and Bioactivity of Cyperus esculentus (C. esculentus L.) before and after Germination

To reveal the effect of germination on nutrient composition of C. esculentus L. and the antioxidant and hypoglycemic activity in vitro of its polysaccharide, a near infrared spectrometer and an amino acid analyzer were applied to analyze the content of starch, fat, protein, fibre, ash and amino acid while anthrone sulfuric acid method was adopted to determine the content of polysaccharides. DPPH·, ABTS⁺· and total antioxidant capacity were used to evaluate the antioxidant activity of C. esculentus L. polysaccharide while PNPG method was employed to observe the hypoglycemic effect of C. esculentus L. polysaccharide with acarbose as control. The results showed that the effects of germination on the nutritional components of C. esculentus L. were different, the fat contents of C. esculentus L. increased by 8.22% while amylose, protein, fibre and ash contents respectively reduced by 11.75%, 11.09%, 10.31% and 7.69% after germination. Furthermore, the total contents of amino acid improved by 8% while the yield of polysaccharides from C. esculentus L. was significantly increased by 9.23%. On the other hand, in the bioactivity assay, the results showed that the antioxidant and hypoglycemic activities of polysaccharides from C. esculentus L. after germination were higher than that of ungerminated. The analysis results of high performance anion exchange chromatography with PAD detector (HPAEC-PAD) showed that germination changed the monosaccharide composition ratio of C. esculentus L. polysaccharide, which produced more monosaccharides (rhamnoose, Rham) with stronger antioxidant activity. Correlation analysis showed that the strong antioxidant activity and α-glucosidase inhibitory activity of germinated C. esculentus L. polysaccharide were significantly correlated with high polysaccharides content (P<0.01, r=0.985~0.997). Mentioned above, our study would provide important scientific reference for the further processing and the development of functional products of C. esculentus L.