Newly generated and increased bound phenolic in lychee pulp during heat-pump drying detected by UPLC-ESI-triple-TOF-MS/MS.

BACKGROUND: During the thermal processing of fruit, it has been observed for phenolic compounds to either degrade, polymerize, or transfer into macromolecules. In this study, the bound and free phenolic compound composition, content, and phenolic-related enzyme activity of lychee pulp were investigated to determine whether the free phenolic had converted to bound phenolic during heat-pump drying (HPD). RESULTS: It was found that after HPD, when compared with the fresh lychee pulp (control), the content of bound phenolics of dried lychee pulp had increased by 62.69%, whereas the content of free phenolics of dried lychee pulp decreased by 22.26%. It was also found that the antioxidant activity of bound phenolics had also increased after drying. With the use of high-performance liquid chromatography-tandem mass spectrometry, it was identified that (+)-gallocatechin, protocatechuic aldehyde, isorhamnetin-3-O-rutoside, 3,4-dihydroxybenzeneacetic acid, and 4-hydroxybenzoic acid were newly generated during HPD, when compared with the control sample. After drying, the contents of gallic acid, catechin, 4-hydroxybenzoic acid, vanillin, syringic acid, and quercetin in bound phenolics had also increased, and polyphenol oxidase and peroxidase still showed enzyme activity, which could be related to the conversion of free phenolics to bound phenolics. CONCLUSION: Overall, during the thermal processing of lychee pulp, the free phenolics weres found to be converted into bound phenolics, new substances were generated, and antioxidant activity was increased. Hence, it was concluded that HPD improved the bound phenolics content of lychee pulp, thus providing theoretical support for the lychee processing industry. © 2021 Society of Chemical Industry.

In vitro simulated digestion and colonic fermentation of lychee pulp phenolics and their impact on metabolic pathways based on fecal metabolomics of mice.

Lychee pulp phenolics (LPP) was subjected to four simulated gastrointestinal digestions and colonic fermentation to investigate the changes in its phenolic composition and bioactivities; the fecal metabolic profiles of LPP-fed mice were also elucidated using UHPLC-ESI-QTOF-MS/MS. After simulated salivary, gastric and intestinal digestion, slight increases in phenolic acids and (+)-catechin occurred relative to undigested LPP, whereas other flavonoids showed an opposite trend. Unlike the above-described separate simulated digestions, successive gastrointestinal digestion significantly enhanced the release of phenolic compounds (p < 0.05), gallic acid (413.79%), ferulic acid (393.69%), (+)-catechin (570.27%) and rutin (247.54%). During colonic fermentation, ten detected phenolics were utilized by gut microbes, among which procyanidin B2 (22.35%) was the most degraded. LPP fermentation accelerated the production of short-chain fatty acids (122.79%). The metabolic pathways altered by LPP including unsaturated fatty acid, biotin, and nicotinamide metabolism may be the potential regulatory mechanisms and associated with the integrity of the gut barrier. These findings indicate that LPP may act as a promising candidate to protect gut health.

Effects of Maydis stigma polysaccharide on the intestinal microflora in type-2 diabetes.

CONTEXT: Diabetes is a serious endocrine and metabolic disorder. Food supplements attract people's attention in mitigating health problems from the aspect of gastrointestinal microflora. Maydis stigma (Zea mays subsp. mays L. [Poaceae]), has been used as water decoction for treating diabetes in folk medicine. It has great potential, and feasibly a stable form of Maydis stigma commercial products could be developed to fulfil the health food market. OBJECTIVE: To study the effects of Maydis stigma polysaccharide (MSP) on the intestinal microflora in type-2 diabetes (T2D). MATERIALS AND METHODS: MSP was fractioned from Maydis stigma by distilled water, purified by DEAE-52 Cellulose chromatography and Sephadex G-200 gel column. Streptozotocin (160 mg/kg) was intraperitoneal injected for 3 days to build model. The diabetic mice were randomly divided into five groups together with control group (10 mice in each group). The doses of MSP were 400, 600 and 800 mg/kg, respectively. After 5 weeks of administration, antidiabetic effects and intestinal microflora balance restoring activities were evaluated by denaturing gradient gel electrophoresis. RESULTS: Blood glucose levels of MSP-treated groups showed extremely significant hypoglycemic effects (p < 0.01), body weight increased showed extremely significant (p < 0.01) differences. Bacteroides, Lactobacillus and Prevotella were dominant organisms in the intestinal tract. The quality and quantity of Lactobacillus and Bacteroides genus increased remarkably with increasing concentration of MSP. DISCUSSION AND CONCLUSION: Experimental results of this study suggest that MSP has the significant potential to be used as a natural agent for treating T2D and restoring the intestinal microflora balance.

In vitro effects on intestinal bacterium of physalins from Physalis alkekengi var. Francheti.

Intestinal probiotic bacterium stimulative activity-guided fractionation of Physalis alkekengi var. Francheti calyces extract resulted in the isolation of four new physalins (1-4). Their structures were elucidated as 5α, 6ß-dihydroxy-25, 27-dihydro-7-deoxyphysalin A (1), 5α, 6ß-dihydroxyphysalin R (2), 3ß-hydroxy-2-hydrophysalin A (3) and 5α-hydroxy-7-dehydro-25, 27-dihydro-7-deoxyneophysalin A (4) by UV, MS, 1D and 2D NMR spectroscopy. Growth curves of Lactobacillus delbrueckii and Escherichia coli for different total physalins extract (TPE) concentrations were tested in vitro. Middle concentrations (0.78mg/mL-1.56mg/mL) of TPE promoted the growth of L. delbrueckii, but all inhibited the growth of E. coli, in which the bacteriostatic activity increased while TPE concentration increases. Physalins showed stimulative effects on the growth of probiotic bacteria but inhibitory effects on the growth of pathogenic bacteria.