Citrus grandis Osbeck, commonly known as “pomelo” or “shaddock,” is the largest citrus fruit, the peel of which is a well‐known agricultural residual waste. Pomelo peel offers a wide range of components such as essential oils, polysaccharides, and phytochemicals with potential food applications. Utilization of pomelo peel to recover these components is an important step toward agricultural sustainability. This review covers pomelo peel utilization opportunities beyond conventional composting and animal feed production, and critically examines value‐added uses via the recovery of potentially bioactive components. The peel of pomelo accounts for approximately 30% of the total fruit weight and contains phytochemicals, including aroma‐active volatiles, pectin, flavonoids, phenolic acids, carotenoids, coumarins, and polysaccharides. Recovery of these phytochemicals offers an opportunity for value‐added utilization such as the development of enriched or functional foods and nutraceuticals. The health‐promoting and therapeutic potential of pomelo peel extracts and isolated pure compounds have been evaluated through numerous in vitro and in vivo studies that revealed a wide range of bioactivities, including hypolipidemic, hypoglycemic, antioxidant, antimicrobial, anti‐inflammatory, and anticancer effects. Preclinical evidence highlights multifaceted molecular and signaling events that possibly underlie the said bioactive potential. Overall, the pomelo processing industry offers a great opportunity to recover or produce valuable products from the large amounts of residual wastes it generates. It is envisaged that a thorough understanding of the bioactive components of pomelo peel, their functional and nutraceutical applications, and mode of actions will benefit the food industry.

Foods that are rich in organosulfides are highly regarded for their broad range of functions in disease prevention and health promotion since ancient time yet modern scientific study, particularly clinical studies could not agree with traditional wisdom. One of the complexities is due to the labile nature of organosulfides, which are often transformed to different structures depending on the processing conditions. The recent evidence on polysulfides as H₂S donors may open up a new avenue for establishing structure and health promotion activity relationship. To put this development into perspective, we carried out a review on the recent progress on the chemistry and biochemistry of organopolysulfides with emphasis on their cardioprotective property. First, we briefly surveyed the foods that are rich in polysulfides and their structural diversity. This is followed by in-depth discussion on the chemical transformations of polysulfides under various processing conditions. We further reviewed the potential action mechanisms of polysulfides in cardioprotection through: (a) hydrogen sulfide releasing activity; (b) radical scavenging activity; and (c) activity in enzyme inhibition and intervention of gene regulation pathways. Based on the literature trend, we can conclude that the emerging concept of organopolysulfides as naturally occurring H₂S donors is intriguing and warrants further research to establish the structure and activity relationship of the organopolysulfides as H₂S donors.

A mechanistic understanding of microbe-host interactions is critical to developing therapeutic strategies for targeted modulation of the host immune system. Different members of the gut symbiont species Lactobacillus reuteri modulate host health by, for example, reduction of intestinal inflammation. Previously, it was shown that L. reuteri activates the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that plays an important role in the mucosal immune system, by the production of tryptophan catabolites. Here, we identified a novel pathway by which L. reuteri activates AhR, which is independent of tryptophan metabolism. We screened a library of 36 L. reuteri strains and determined that R2lc and 2010, strains with a pigmented phenotype, are potent AhR activators. By whole-genome sequencing and comparative genomics, we identified genes unique to R2lc and 2010. Our analyses demonstrated that R2lc harbors two genetically distinct polyketide synthase (PKS) clusters, functionally unknown (fun) and pks, each carried by a multicopy plasmid. Inactivation of pks, but not fun, abolished the ability of R2lc to activate AhR. L. reuteri 2010 has a gene cluster homologous to the pks cluster in R2lc with an identical gene organization, which is also responsible for AhR activation. In conclusion, we identified a novel PKS pathway in L. reuteri R2lc and 2010 that is responsible for AhR activation. IMPORTANCE Temporary changes in the composition of the microbiota, for example, by oral administration of probiotics, can modulate the host immune system. However, the underlying mechanisms by which probiotics interact with the host are often unknown. Here, we show that Lactobacillus reuteri R2lc and 2010 harbor an orthologous PKS gene cluster that activates the aryl hydrocarbon receptor (AhR). AhR is a ligand-activated transcription factor that plays a key role in a variety of diseases, including amelioration of intestinal inflammation. Understanding the mechanism by which a bacterium modulates the immune system is critical for applying rational selection strategies for probiotic supplementation. Finally, heterologous and/or optimized expression of PKS is a logical next step toward the development of next-generation probiotics to prevent and treat disease.