Bioaccessibility of phenolic compounds in Psidium guajava L. varieties and P. friedrichsthalianum Nied. after gastrointestinal digestion.

Psidium guajava L. and Psidium friedrichsthalianum Nied are part of the Psidium species native to America. Nowadays, it is essential to study the phenolic compound (PC) profile and their changes during digestion and the fractions available for absorption. This study aimed to characterize the PC profile in some Psidium species and their bioaccessibility (BA). Fifty-seven compounds were identified, and forty-six belonged to ten different phenolic classes. PC profiles showed significant differences between the species and the intestinal fraction P. friedrichsthalianum Nied. showed the highest PC content, although it mostly belonged to non-extractable polyphenols. This leads to the lowest BA (37%); P. guajava L. 'Morada' showed the highest (47%). Hydroxycinnamic acids were the most stable PC after gastrointestinal digestion. This study showed relevant differences in the PC content and profile of different Psidium species and changes between the PC in the original matrix and those released in the different stages of gastrointestinal digestion.

In Vitro Intestinal Bioaccessibility and Colonic Biotransformation of Polyphenols from Mini Bell Peppers (Capsicum annuum L.).

To the best of our knowledge, "sweet mini bell" peppers have not been extensively investigated. In this study, we evaluated the bioaccessible phenolic compounds released during intestinal digestion and identified and quantified the microbial metabolites derived from phenolic compounds bioconversion during the in vitro colonic fermentation. A total of 66 phenolic compounds were determined. The results obtained in this study indicate that hydroxycinnamic acids (22 to 32 mg/100 g dw) and flavonoids (99 to 102 mg/100 g dw) headed by quercetin, luteolin and kaempferol glycosidic derivatives were the main bioaccessible phenolic compounds during in vitro intestinal digestion of mini bell peppers. The yellow variety contained the highest concentration of bioaccessible flavonoids (80 mg/100 g dw). For the first time in mini bell peppers, dihydroferulic acid was detected, in the three varieties studied. 3-(4-hydroxyphenyl)propionic acid was the major metabolite found after 12-24 h fermentation of all samples (44 to 102 µM/L). Further cell culture or in vivo studies are needed to elucidate the biological activities of the phenolic compounds identified in mini bell peppers.

In vitro gastrointestinal digestion and colonic fermentation of tomato (Solanum lycopersicum L.) and husk tomato (Physalis ixocarpa Brot.): Phenolic compounds released and bioconverted by gut microbiota.

Two of the most important Mexican plant-foods are tomato (Solanum lycopersicum L.) and husk tomato (Physalis ixocarpa Brot.). In this study three objectives were followed: i) to evaluate the bioaccessible phenolic compounds (PC) in T and HT during upper gastrointestinal digestion, ii) to in vitro ferment the indigestible fractions of the samples to evaluate the short-chain fatty acids (SCFA) production, iii) the microbial metabolites, bioconverted PC and volatile organic compounds (VOCs) generated during the fermentation. Vanillic acid was the most bioaccessible PC and after 48 h, 3-hydroxyphenylacetic acid was the most abundant microbial metabolite identified in both samples. The identification of VOCs belonging to terpenes (and derivatives) group in T and HT can be product of the microbial metabolism of carotenoids. The study shows new knowledge of the in vitro intestinal digestion and fermentation of T and HT final compounds with biological potential which should be evaluated in further studies.

Stability and anti-topoisomerase activity of phenolic compounds of Capsicum annuum "Serrano" after gastrointestinal digestion and in vitro colonic fermentation.

"Serrano" pepper is extensively used in Mexican cuisine. The aim of this study was to identify the bioaccessible phenolic compounds (PC) of "Serrano" pepper as well as short-chain fatty acids (SCFA) produced and PC bioconverted using an in vitro step-wise gastromimetic model of the intestinal digestion and anaerobic fermentation of the isolated indigestible fraction (IF). The anti-topoisomerase activity of the fermented samples was also evaluated. PC bioaccessibility was about 45% in the small intestine. Chlorogenic acid and capsaicin were identified during the intestinal digestion, while quercetin was identified as available to the gut microbiota. After 48-h fermentation, SCFA molar ratio was 77:11:12 for acetic, propionic and butyric acid. The PC identified in IF and after 12 h of fermentation showed anti-topoisomerase activity. A synergistic effect among the PC and gut metabolites mixture was observed, which indicates a possible antiproliferative mechanism that should be tested in further studies.

In Vitro Gastrointestinal Digestion and Colonic Fermentation of High Dietary Fiber and Antioxidant-Rich Mango (Mangifera indica L.) "Ataulfo"-Based Fruit Bars.

Mango (Mangifera indica L.) is a tropical fruit which is considered to be a source of dietary fiber (DF) and phenolic compounds (PCs). In this study, high DF mango-based fruit bars were developed from whole mango (peel and pulp). The bars were evaluated for their nutritional composition, the bioaccesibility of PCs during gastrointestinal digestion, and the PCs metabolites profile after in vitro colonic fermentation. The amount of DF in a 30 g portion of mango bars was 9.5 g, i.e., 35% of the recommended daily intake. Phenolic acids such as gallic acid; cinnamic acids, such as ferulic, coumaric, and caffeic acids; flavonoids such as quercertin; and xanthones such as mangiferin and mangiferin gallate, were identified as the main PCs in the bars. The antioxidant capacity associated with the PCs profile, together with the high DF content are indicative of the potential functional features of these natural fruit bars. The bioaccesibility of PCs in the mango bar was 53.78%. During fermentation, the PCs were bioconverted mainly to hydroxyphenolic acids and the main short-chain fatty acid produced was acetic acid. The xanthone norathyriol was identified after 12 h of fermentation. This study on the digestion and colonic fermentation of mango-based bars using in vitro models provides hints of the potential physiological behavior of PCs associated with DF, which constitutes relevant information for further development of natural and health-promoting fruit-based bars.