Polyphenols are plant-derived natural products with well-documented health benefits to human beings, such as antibacterial activities. However, the antibacterial activities of polyphenols under hyperglycemic conditions have been rarely studied, which could be relevant to their antibacterial efficacy in disease conditions, such as in diabetic patients. Herein, the antibacterial activities of 38 polyphenols under mimicked hyperglycemic conditions were evaluated. The structure-antibacterial activity relationships of polyphenols were also tested and analyzed. The presence of glucose apparently promoted the growth of the bacterial strains tested in this study. The OD600 values of tested bacteria strains increased from 1.09-fold to 1.49-fold by adding 800 mg/dL glucose. The polyphenols showed structurally dependent antibacterial activities, which were significantly impaired under the hyperglycemic conditions. The results from this study indicated that high blood glucose might promote bacterial infection, and the hyperglycemic conditions resulting from diabetes were likely to suppress the antibacterial benefits of polyphenols.

Polyphenols have been used as natural medicaments for the management of hyperuricemia for a long history. They have been attracted many interests because of the little side effects in curing hyperuricemia, which is an important advantage over the antihyperuricemic drugs. In this review, the structure–activity relationships for polyphenols as xanthine oxidase (XO) inhibitors were discussed. It is concluded that the presence of hydroxyl groups, which influences the inhibitory effects, is closely related to whether the substitutions increase the steric hindrance or disturb the interaction of flavonoid with the catalytic site of XO, and the increased size of the molecule after glycosylation may increase the steric hindrance between flavonoid and XO, and consequently reducing the competitive inhibition behaviors. However, there is no obtained simple general rule that can comprehensively describe the effects of structural alteration on the inhibition activity because the results are varied among different subclasses of polyphenols. In addition, the inhibition mechanisms are mainly assumed as polyphenol binding to the active site of XO and hindering the entrance of xanthine or the discharge of uric acid and diffusion of O²⁻radical.