It is widely acknowledged that the excessive reactive oxygen species (ROS) or reactive nitrogen species (RNS) induced oxidative stress will cause significant damage to cell structure and biomolecular function, directly or indirectly leading to a number of diseases. The overproduction of ROS/RNS will be balanced by nonenzymatic antioxidants and antioxidant enzymes. Polysaccharide or glycoconjugates derived from natural products are of considerable interest from the viewpoint of potent in vivo and in vitro antioxidant activities recently. Particularly, with regard to the in vitro antioxidant systems, polysaccharides are considered as effective free radical scavenger, reducing agent, and ferrous chelator in most of the reports. However, the underlying mechanisms of these antioxidant actions have not been illustrated systematically and sometimes controversial results appeared among various literatures. To address this issue, we summarized the latest discoveries and advancements in the study of antioxidative polysaccharides and gave a detailed description of the possible mechanisms.

Firmicutes and Bacteroidetes are the predominant bacterial phyla colonizing the healthy human gut. Accumulating evidence suggests that dietary fiber plays a crucial role in host health, yet most studies have focused on how the dietary fiber affects health through gut Bacteroides. More recently, gut Firmicutes have been found to possess many genes responsible for fermenting dietary fiber, and could also interact with the intestinal mucosa and thereby contribute to homeostasis. Consequently, the relationship between dietary fiber and Firmicutes is of interest, as well as the role of Firmicutes in host health. In this review, we summarize the current knowledge regarding the molecular mechanism of dietary fiber degradation by gut Firmicutes and explain the communication pathway of the dietary fiber-Firmicutes-host axis, and the beneficial effects of dietary fiber-induced Firmicutes and their metabolites on health. A better understanding of the dialogue sustained by the dietary fiber-Firmicutes axis and the host could provide new insights into probiotic therapy and novel dietary interventions aimed at increasing the abundance of Firmicutes (such as Faecalibacterium, Lactobacillus, and Roseburia) to promote health. Graphical Abstract

Diabetes mellitus (DM) and its complications are major public health concerns which strongly influence the quality of humans’ life. Modification of gut microbiota has been widely used for the management of diabetes. In this review, the relationship between diabetes and gut microbiota, as well as the effects of different dietary components and traditional Chinese medicine (TCM) on gut microflora are summarized. Dietary compounds and TCM possessing bioactive components (fiber and phytochemicals) first change the composition of gut microbiota (inhibiting pathogens and promoting the beneficial bacteria growth) and then influence the production of their metabolites, which would further modify the intestinal environment through inhibiting the production of detrimental compounds (such as lipopolysaccharide, hydrogen sulfide, indol, etc.). Importantly, metabolites (short chain fatty acids and other bioactive components) fermented/degraded by gut microbiota can target multiple pathways in intestine, liver, pancreas, etc., resulting in the improvement of gut health, glycemic control, lipids profile, insulin resistance and inflammation. Furthermore, understanding the interaction between different dietary components and gut microbiota, as well as underlying mechanisms would help design different diet formula for the management of diabetes. Further researches could focus on the combination of different dietary components for preventing and treating diabetes, based on the principle of “multiple components against multiple targets” from the perspective of gut microbiota.