# Effects of _Gynura bicolor_ on Glycemic Control and Antioxidant Ability in Predicates
## 4 Discussion
A previous study observed that Aronia extract results from the influence of anthocyanins and possibly other flavonoids on decreasing MDA and catalase and increasing GSH-Px and superoxide dismutase activities [46]. In our study, we excluded smoker and alcohol consumption subjects. MDA and GSH-Px in the GB group were decreased/increased in Week 8 when compared with baseline, respectively. It showed that, after an 8-week intervention, the oxidative stress in subjects was decreased. Because of increasing oxidative stress, the pathophysiology of preDM and T2D were considered as a chronic inflammation. IL-6 is an important mediator of inflammatory response [47]. [PERSON] et al. observed that TNF-\(\alpha\) and IL-6 were significantly higher in overweight/obese young subjects with preDM (BMI > 33 kg/m\({}^{2}\)) than healthy overweight/obese ones [48]. It is not consistent with our study. We speculated that this is because the study population consisted of all overweight individuals (BMI > 25 kg/m\({}^{2}\)). The inflammation generated from adipocytes was fewer than obesity. The bioavailability of polyphenols was influenced by the molecular weight, conjugated form (methyl, glucuronide or sulphate) and cooking method. For most flavonoids absorbed in the small intestine, the plasma concentration then rapidly decreases (elimination half-life period of 1-2 h). The maintenance of a high concentration in plasma thus requires a repeated ingestion of the polyphenols over time. Anthocyanins are quite rapidly absorbed, but their bioavailability seems to be the lowest of all flavonoids [40]. [PERSON] et al. concluded that urinary flavonoids may be useful as a new biomarker for vegetables and fruits [49]. In the GB group, there were no differences in total polyphenols of plasma. It could be associated with the fact that the blood sample collection of subjects was not conducted all at the same time. When all were finished to collect, it already passed the half-life time of polyphenols. In the control group, total polyphenols of plasma were significantly decreased. It might be associated with prohibiting eating red-purple food for 8 weeks. We suggested that future studies must use urine tests to assess total polyphenol intake. Our study was the first interventional trial using GB for preDM, by using natural ingredients and at least eating two exchanges of vegetables every day. GB is not only rich in fiber; it also contains higher polyphenols than other green-leafy vegetables. This might have resulted in improvement of glycemic control and reducing oxidative stress in preDM subjects. Although the beneficial effects of GB could be observed, some limitations needed be addressed. (1) PreDM without medication subjects are difficult to find, because people pay less attention to their own blood report. (2) The intervention period was 8 weeks. We did not consider that the half-life of HbA1c is about 3 months. (3) The baseline characteristics had biases between the control group and GB group. This is because we did not assign randomly, but based on subjects' dietary habit. Further studies, we suggest, should consider expanding the intervention time and the allocations of groups. In conclusion, the subjects in our study were overweight and preDM subjects. After intervention of two serving sizes of GB for 8 weeks, FPG and MDA were decreased, FRAP and GSH-Px were increased in the intervention group and HOMA-IR and QUICKI were improved. We concluded that GB could improve glycemic control and decrease oxidative stress because of its large amounts of polyphenols. In addition, GB not only has health-care functions, but its pigments also show potential uses as natural food colorings. Therefore, GB extract can be used to make functional foods, such as adding to fruit mousse or yogurt. [PERSON] and [PERSON] were involved in the conceptualization and the design of this study. [PERSON] conducted this study and biochemical analyses. [PERSON] wrote the original draft preparation. [PERSON] and [PERSON] reviewed and edited this study. [PERSON] supervised this study.