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Objective: To develop a method to quantitatively analyze the residues of six pesticides (carbendazim, tricyclozole, bensulfuron methyl, triazophos, chlorpyrifos and carbosulfan) in paddy and rice by quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and to propose a quantitative model for pesticide residues using Minitab software. Methods: Positive samples were prepared by spraying pesticide mixture solution on paddy and rice, and stored at constant temperature and relative humidity conditions simulating those in grain depot. Temperature and relative humidity as key variables were set at different levels, namely 20, 30, 40 and 50 ℃; and 50%, 60%, 70% and 80%. Results: The calibration curves for the six pesticides showed good linearity in the concentration range of 5.0–1 000.0 μg/L with correlation coefficient (R2) greater than 0.999 0, the detection limits were in the range of 0.000 1–0.005 mg/kg, the average spiked recoveries were in the range of 84.02%–103.24%, and the precision, expressed as relative standard deviation (RSD), was in the range of 3.65%–8.29%. Therefore, the QuEChERS-UPLC-MS/MS method can meet the requirements of the analysis and detection of pesticide residues. The quantitative model of pesticide degradation during the whole process from paddy to rice, developed by the processing factors investigated, showed R2 value above 0.769. Among them, the R2 values for carbendazim, bensulfuron, triazophos and chlorpyrifos in paddy were greater than 0.9, and those for triazophos and butachlor in rice were also greater than 0.9, indicating good fitness. The residues of the six pesticides in the positive samples gradually decreased with storage time, and the degradation rate of pesticide residues changed with storage environment. Conclusion: The QuEChERS-UPLC-MS/MS method is simple, rapid, and accurate and suitable for the detection of the six pesticide residues in paddy and rice. The quantitative model of pesticide degradation during the whole process from paddy to rice is well fitted, and the degradation patterns of pesticide residues in paddy and rice under different storage conditions are different. This study has important significance to improve the comprehensive benefits of the grain industry.

The hypoglycemic activity of lotus seedpod procyanidin was investigated in a Wistar rat model of diabetes mellitus induced by streptozotocin, and its mechanism of action was preliminarily explored. The rats were divided into six groups: blank control, diabetic model, and lotus seedpod procyanidin at low, medium and high doses. Body mass, food and water intake, fasting blood glucose, serum insulin, C-peptide concentration, oxidative stress, total cholesterol (TC) concentration, triglyceride (TG) concentration and organ indices were measured in each group of mice, and the pathological changes of liver and kidney tissues were also observed. The results showed that lotus seedpod procyanidin alleviated mass loss in diabetic rats. Compared with the model group, high-dose lotus seedpod procyanidin significantly or extremely significantly reduced food and water intake, and fasting blood glucose, serum TC and TG concentrations in rats (P < 0.05, P < 0.01). Medium- and high-dose lotus seedpod procyanidin extremely significantly reduced serum malondialdehyde (MDA) concentration (P < 0.01) and significantly or extremely significantly increased the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) (P < 0.05, P < 0.01), thus improving oxidative stress in diabetic rats. Microscopic observation of rat liver and kidney sections indicated that lotus seedpod procyanidin could protect liver and kidney tissues to a certain extent. In conclusion, lotus seedpod procyanidin has a significant hypoglycemic effect, possibly by affecting lipid metabolism and protecting rats from oxidative stress.