Protective Effect of Effective Components of Coreopsis tinctoria Nutt on Retinopathy of db/db Diabetic Mice

Objective. Diabetic retinopathy (DR) is one of the main diabetic microvascular complications in clinical practice, which features a complicated mechanism and insignificant efficacy. Therefore, it is urgent to find effective drugs. Xinjiang Coreopsis tinctoria Nutt is a rare alpine wild plant with unique effects and extremely high medicinal value. Preliminary studies have shown that it can reduce elevated blood sugar, unhealthy lipids, and antioxidants. This study was intended to investigate the protective effect of the effective components of Coreopsis tinctoria Nutt on the retinopathy of db/db diabetic mice and provide experimental basis for exploring the efficacy of Coreopsis tinctoria Nutt and the development of new drugs for the treatment of DR. Method. The db/db diabetic mouse models were used, and the effective components of Coreopsis tinctoria Nutt were obtained from Coreopsis tinctoria Nutt using macroporous resin enrichment method after alcohol extraction. These mice were divided into the normal group, model group, and high-dose Coreopsis tinctoria Nutt groups, the positive drug metformin group, and the metformin and Coreopsis tinctoria Nutt combination group. After these db/db type 2 diabetes mouse models were intervened for 10 weeks, their weight, blood sugar, glycosylated hemoglobin, serum MDA, SOD, and other indicators of each group were tested, and the expression changes of VEGF, ICAM1, PEDF, Bcl-2 in mouse retina were observed by immunohistochemistry method. Result. The effective components of Coreopsis tinctoria Nutt were obtained using macroporous resin enrichment method after alcohol extraction, which were mainly comprised of chlorogenic acid, flavone mariside, mariside, dicaffeoyl quinic acid, and flavone oxanine, with a total content of 532.82 mg/g, and the total flavonoid content of 330 mg/g. The effective components of Coreopsis tinctoria Nutt significantly reduced blood sugar and glycosylated hemoglobin and improved oxidative stress levels in db/db diabetic mice. Meanwhile, they reduced the expression of VEGF and ICAM1 in retinopathy and increased the expression of Bcl-2 and PEDF. The combination of Coreopsis tinctoria Nutt and metformin has the most significant effect. Conclusion. Coreopsis tinctoria Nutt can prevent and treat early diabetic retinopathy by affecting the expression of retinopathy-related factors.

Carbon and nitrogen metabolism under nitrogen variation affects flavonoid accumulation in the leaves of Coreopsis tinctoria

Flavonoids are phytochemicals present in medicinal plants and contribute to human health. Coreopsis tinctoria, a species rich in flavonoids, has long been used in traditional medicine and as a food resource. N (nitrogen) fertilization can reduce flavonoid accumulation in C. tinctoria. However, there is limited knowledge regarding N regulatory mechanisms. The aim of this study was to determine the effect of N availability on flavonoid biosynthesis in C. tinctoria and to investigate the relationship between C (carbon) and N metabolism coupled with flavonoid synthesis under controlled conditions. C. tinctoria seedlings were grown hydroponically under five different N levels (0, 0.625, 1.250, 2.500 and 5.000 mM). The related indexes of C, N and flavonoid metabolism of C. tinctoria under N variation were measured and analysed. N availability (low and moderate N levels) regulates enzyme activities related to C and N metabolism, promotes the accumulation of carbohydrates, reduces N metabolite levels, and enhances the internal C/N balance. The flavonoid content in roots and stalks remained relatively stable, while that in leaves peaked at low or intermediate N levels. Flavonoids are closely related to phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), 4-coumarate: coenzyme A ligase (4CL), and chalcone-thioase (CHS) activity, significantly positively correlated with carbohydrates and negatively correlated with N metabolites. Thus, C and N metabolism can not only control the distribution of C in amino acid and carbohydrate biosynthesis pathways but also change the distribution in flavonoid biosynthesis pathways, which also provides meaningful information for maintaining high yields while ensuring the nutritional value of crop plants.

Physiological changes and transcript identification in Coreopsis tinctoria Nutt. in early stages of salt stress

Coreopsis tinctoria Nutt. (C. tinctoria) is a special tea ingredient that adapts to certain salt stresses and shares the functions of chrysanthemum. With annual expansion of the cultivation area of C. tinctoria in Xinjiang (China), soil salinity may become a constraint for chrysanthemum cultivation. To investigate the response of C. tinctoria to salt stress, physiological and transcriptional changes in C. tinctoria in the early stages of low (50 mM NaCl) and high (200 mM NaCl) salt stress were analyzed and identified. The results showed that the contents of osmotic regulators (free proline, soluble sugar, and soluble protein) and antioxidant enzymes (catalase and peroxidase) under salt stress increased to various extents compared with those of the control (CK) within 72 h, and the increase was higher under 200 mM NaCl treatments. De novo RNA-seq was used to analyze changes in the transcripts under 50 and 200 mM NaCl treatments for up to 48 h. In total, 8,584, 3,760, 7,833, 19,341, 13,233, and 9,224 differentially expressed genes (DEGs) were detected under 12 h, 24 h, and 48 h for 50 and 200 mM NaCl treatments, respectively. Weighted correlation network analysis (WGCNA) was used to analyze the correlations between all DEGs and physiological indexes. We found that the coexpression modules blue2 and Lightskyblue4 highly correlated with osmotic regulators and CAT and identified 20 and 30 hub genes, respectively. The results provide useful data for the further study of salt tolerance in C. tinctoria.

Effects of Salt Stress on Photosynthetic Fluorescence Characteristics, Antioxidant System, and Osmoregulation of Coreopsis tinctoria Nutt.

Coreopsis tinctoria Nutt. (C. tinctoria) is used in composite tea material and has important medicinal functions. Soil salinization affects the growth and development of C. tinctoria in Xinjiang (China). Here, we discussed the changes in photosynthesis and physiological characteristics of C. tinctoria seedlings treated with different concentrations of NaCl [0 (CK), 50, 100, 150, 200, and 250 mmol·L−1] for 12, 24, and 72 hours. The results showed that the net photosynthetic rate (Pn), stomatal conductance (gS), transpiration rate (Tr), and stomatal inhibition rate (Ls) decreased significantly with increasing concentrations of NaCl. Salt stress promoted the accumulation of peroxidase (POD), catalase (CAT), soluble sugar, soluble protein, and free proline (Pro). A highly significant positive correlation was found between Ls and Fv/Fm; Ls and Fv/Fo; soluble sugar and CAT; soluble sugar and soluble protein. C. tinctoria was most sensitive to the concentrations of 150 to 250 mmol·L−1 NaCl, and its salt stress tolerance was increased by reducing photosynthetic fluorescence parameters, improving the antioxidant enzyme system, and regulating osmotic substances.

Nitrogen deficiency maintains the yield and improves the antioxidant activity of Coreopsis tinctoria Nutt

Nitrogen (N) deficiency levels were investigated for their potential to maintain the yield and improve antioxidant activity of Coreopsis tinctoria. Inflorescences and leaves at 0, 10, 20, 30, 40 and 50 d after flowering were frozen at −80 °C and plant growth, antioxidant activity, bioactive substance, enzyme activity and gene expression were evaluated. N deficiency maintained the total number of flowers, promoted phenol and flavonoid accumulation and enhanced antioxidant activity. Moreover, N deficiency stimulated activities of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H) and 4-coumarate: coenzyme A ligase (4CL) and induced CtPAL, CtC4H and Ct4CL gene expression. The data also suggest that N deficiency-induced phenolic and flavonoid accumulation occurs due to the activation of biosynthetic pathways in C. tinctoria. We characterize the unique features of C. tinctoria under N deficiency conditions and provide valuable information for the cultivation of high-N use efficiency varieties with low input and high output.

Effects of ethyl acetate extract from Coreopsis tinctoria on learning and memory impairment in d-galactose-induced aging mice and the underlying molecular mechanism

The aim of this study was to investigate the effects of ethyl acetate extract from Coreopsis tinctoria (EACC) on learning and memory impairment in d-galactose-induced aging mice and the underlying molecular mechanism.