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Chestnut pellicle has attracted lots of interests for its rich polyphenol content. However, little is known about the investigation of antioxidant activity of its different solvent extractions and applications in oil and oil-based food preservation. Here, we investigated the polyphenol contents of three chestnut pellicle extracts (CPEs) using different extractant, and found that chestnut pellicle ethanol extract (CPEE) exhibited the highest contents of total phenolic, while chestnut pellicle water extract (CPWE) possessed the highest contents of total flavonoid. What's more, chestnut pellicle ethyl acetate extract (CPEAE) exhibited excellent radical scavenging activity in 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radical. Additionally, CPEAE significantly reduced the lipid peroxide value (PV) in rapeseed oil and lard system. Finally, HPLC–ESI–MS/MS analysis demonstrated that CPEAE mainly contained oligomers of procyanidins and glycosides. These results suggested that chestnut pellicle may be a new potential source of antioxidant and promising candidate of natural additive in cooking oil preservation and other functional foods development. [ABSTRACT FROM AUTHOR]

BACKGROUND: Chestnut (Castanea mollissima) shell is rich in flavonoids and our previous studies showed that proanthocyanins and anthocyanins were the two markedly varied flavonoids in chestnut shell extracts (CSE) during digestion. Here, the biotransformation of proanthocyanins and anthocyanins in a simulated gastrointestinal model, and the interactions between non‐absorption CSE (NACSE) and gut microbiota in vitro, were investigated by ultra‐high‐performance liquid chromatography combined with triple‐quadrupole mass spectrometry and 16S rRNA sequencing. RESULTS: Chestnut shell was richer in proanthocyanins and anthocyanins, while the loss of proanthocyanins was greater after digestion. Additionally, the content of anthocyanin decreased after gastric digestion but increased after intestinal digestion and remained stable after fermentation. After fermentation, delphinidin‐3‐O‐sambubioside and pelargonidin‐3‐O‐galactoside were newly formed. Furthermore, microbiome profiling indicated that NACSE promoted the proliferation of beneficial bacteria, while inhibiting pathogenic bacteria. CONCLUSION: All these data suggest that CSE may be a promising candidate to protect gut health. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Chestnut shell, a by-product of chestnut processing, is rich in bioactive polyphenols, which can be divided into extractable polyphenols (EPs) and non-extractable phenols (NEPs). The EPs have arisen a lot of interests, while NEPs combined with cellulose in the residue are ignored. This work describes the development of a traditional ethanol extraction method to obtain extractable polyphenols (EPs), and the residue was treated by alkaline hydrolysis to prepare NEPs optimized by Box–Behnken experimental designs. The total phenolic contents and the scavenging effects of DPPH and ABTS+ free radicals were measured. Using UPLC–ESI-MS/MS technology, combined with principal component analysis (PCA) and orthogonal partial least square discriminant analysis (OPLS-DA), qualitative and quantitative analysis and difference analysis of EPs and NEPs were carried out. Optimal extraction conditions to extract NEPs by alkaline hydrolysis method were obtained, and the content of polyphenols obtained from NEPs was significantly higher than that of EPs. EPs have the higher scavenging effects of DPPH and ABTS+ free radicals than NEPs. A total of 466 polyphenol compounds were detected. Among them, EPs are rich in flavonoids, phenolic acids, tannins, lignans coumarins and quinones, while phenolic acids were dominant in NEPs, which provides a reference for the utilization of polyphenols from the chestnut shell. Both EPs and NEPs are abundant in phenolic composition, although there were significant differences in the compositional situation. Notably, NEPs are a widespread source of polyphenols but have not received much attention in practical applications. This study can provide a basis for the reuse of chestnut waste. [ABSTRACT FROM AUTHOR]

• The phenolic profile of COE and CIE before and after digestion were studied. • The antioxidant activity of COE and CIE in vitro digestion were detected. • Widely targeted metabolomics was used to study the biotransformation of polyphenols. • The relationship between biotransformation and antioxidant activity are clarified. Chestnut skin is rich in polyphenols that have been linked to health for their antioxidant activity. However, chestnut outer-skin extract (COE), chestnut inner-skin extract (CIE), and their digested products have different compositions of polyphenols, and therefore their antioxidant activities might differ as well. Here, we study the effect of in vitro digestion on their total phenol content, antioxidant capacity, and individual phenolic profile to clarify the relationship between biotransformation and antioxidant activity. Compared to undigested samples, total phenol content and antioxidant activity of digested chestnut outer-skin extract (DCOE) and digested chestnut inner-skin extract (DCIE) had significantly higher values. The changes of phenolic composition and antioxidant activity after digestion were mainly due to the anthocyanin biosynthesis involving glycosylation, acylation, methoxylation and their reverse processes. All these data suggest that as chestnut processing by-products, COE and CIE are raw material sources of antioxidant-rich active substances and need more sufficient utilization. [ABSTRACT FROM AUTHOR]