Kombucha is a popular beverage with various bioactivities (such as antioxidant activity), which can be attributed to its abundant bioactive compounds, especially polyphenols. Kombucha is conventionally prepared by fermentation of a sugared black tea infusion without tea residue. In this study, the effects of black tea residue and green tea residue on kombucha were studied, and its antioxidant activities, total phenolic contents, as well as concentrations of polyphenols at different fermentation stages were evaluated using ferric-reducing antioxidant power, Trolox equivalent antioxidant capacity, Folin-Ciocalteu method and high-performance liquid chromatography with a photodiode array detector. The results showed that fermentation with tea residue could markedly increase antioxidant activities (maximum 3.25 times) as well as polyphenolic concentrations (5.68 times) of kombucha. In addition, green tea residue showed a stronger effect than black tea residue. Overall, it is interesting to find that fermentation with tea residues could be a better strategy to produce polyphenol-rich kombucha beverages.

The gut microbiota and their metabolites could play an important role in health and diseases of human beings. Short-chain fatty acids (SCFAs) are mainly produced by gut microbiome fermentation of dietary fiber and could also be produced by bacteria of the skin and vagina. Acetate, propionate, and butyrate are three major SCFAs, and their bioactivities have been widely studied. The SCFAs have many health benefits, such as anti-inflammatory, immunoregulatory, anti-obesity, anti-diabetes, anticancer, cardiovascular protective, hepatoprotective, and neuroprotective activities. This paper summarizes health benefits and side effects of SCFAs with a special attention paid to the mechanisms of action. This paper provides better support for people eating dietary fiber as well as ways for dietary fiber to be developed into functional food to prevent diseases.

Cancer is the leading cause of death in the world. Curcumin is the main ingredient in turmeric (Curcuma longa L.), and is widely used in the food industry. It shows anticancer properties on different types of cancers, and the underlying mechanisms of action include inhibiting cell proliferation, suppressing invasion and migration, promoting cell apoptosis, inducing autophagy, decreasing cancer stemness, increasing reactive oxygen species production, reducing inflammation, triggering ferroptosis, regulating gut microbiota, and adjuvant therapy. In addition, the anticancer action of curcumin is demonstrated in clinical trials. Moreover, the poor water solubility and low bioavailability of curcumin can be improved by a variety of nanotechnologies, which will promote its clinical effects. Furthermore, although curcumin shows some adverse effects, such as diarrhea and nausea, it is generally safe and tolerable. This paper is an updated review of the prevention and management of cancers by curcumin with a special attention to its mechanisms of action.

Kombucha beverage is commonly prepared by black tea infusion fermentation without tea residues, and possesses various health benefits. In this paper, kombucha beverages of two non-Camellia sinensis teas, including vine tea (Ampelopsisgrossedentata) and sweet tea (Rubus suavissimus), were studied for the first time. The antioxidant activities and polyphenol contents of kombucha beverages were evaluated by ferric-reducing antioxidant power assay, Trolox equivalent antioxidant capacity assay, and Folin-Ciocalteu method, respectively. In addition, effects of tea residues on antioxidant capacities of kombucha beverages were evaluated. The results showed that kombucha beverages from vine tea and sweet tea possessed strong antioxidant activities (especially vine tea kombucha), and fermentation with tea residues could significantly increase antioxidant capacities (maximum increase of 38%) and total phenolic content (maximum increase of 55%) of two kombucha beverages compared with those without tea residues. Moreover, the sensory evaluations showed that the sensory evaluation scores of kombucha with tea residues could be improved compared with those without tea residues. Furthermore, the concentrations of several bioactive components in the kombucha beverages were detected by high-performance liquid chromatography. These kombucha beverages could be used for prevention of several diseases with related of oxidative stress.

Grape (Vitis vinifera L.) is one of the most popular fruits worldwide. It contains various bioactive compounds, such as proanthocyanidins, anthocyanins, flavonols, phenolic acids and stilbenes, the contents of which could vary considerably in grape skin, pulp and seed. Many studies have revealed that grape possesses a variety of health benefits, such as antioxidant, anti-inflammatory, gut-microbiota-modulating, anticancer and cardioprotective effects. Grape is eaten as fresh fruit and is also used as raw material to produce various products, such as wine, grape juice and raisins. Moreover, the byproducts of grape, such as grape pomace and grape seed, have many applications in the food industry. In this paper, the bioactive compounds in grape are briefly summarized based on literature published in recent years. In addition, the health benefits of grape and its bioactive components are discussed, with special attention paid to the underlying mechanisms. Furthermore, the applications of grape in the food industry are elucidated, especially the applications of grape pomace and grape seed. This paper can contribute to understanding the health benefits and mechanisms of grape and its bioactive compounds, as well as the promotion of the use of grape in the food industry.