Abstract
Hibiscus sabdariffa L. (H.s.) is a polyphenolic-rich plant commonly consumed either as a beverage or spice. The aim of the present study was to evaluate the in vitro digestibility of H.s. polyphenols using an in vitro model of digestion which simulates the human stomach and small intestine. The bioaccessible polyphenols released in the digested samples were analyzed by liquid chromatography coupled to photodiode array and mass spectrometry detection. H.s. anthocyanins (cyanidin-3-O-sambubioside and delphinidin-3-O-sambubioside) content drastically dropped during the digestion process from 2.91 ± 0.03 µg g−1 and 8.53 ± 0.08 µg g−1 (w/w) CG (Cyanidin-glucoside) in the raw extract, respectively, to 0.12 ± 0.01 µg g−1 0.12 ± 0.01 µg g−1 (w/w) CG at the end of duodenal digestion. Total polyphenols also have shown a decrease from 1192.65 ± 30.37 µg g−1 (w/w) in the raw extract to 282.24 ± 7.21 µg g−1 (w/w) by the end of gastric digestion, in contrast to their increase by the end of duodenal digestion 372.91 ± 3.97 µg g−1 (w/w). On the other hand, the decrease in certain compounds (e.g., caffeoylquinicandcoumaroylquinic acids) was observed during gastric digestion resulting in an increase of quinic acid in the duodenal aliquots, thus suggesting that this compound was derived from the degradation of the more complex hydroxycinnamic acids. H.s. extract also exhibited a bacteriostatic effect against Staphylococcus aureus ATCC 6538 (MIC of 2.5 mg mL−1) and a bactericidal effect against a food isolate of Listeria monocytogenes (MBC of 2.5 mg mL−1). The undigested polyphenols of H.s. in the upper gastrointestinal tract enters the colon, where they are metabolized by the gut microbiota. The present study results showed that resistance of H.s. polyphenols during gastrointestinal digestion might affect their uptake, resulting in a decrease in their digestibility.
Highlights
Hibiscus sabdariffa (H.s.), which belongs to the family of Malvaceae, is commonly known as asroselle, bissap, or karkade
In previous studies we evaluated the release of lipids, proteins, and polyphenols during simulated human digestion from natural and blanched skins [8] and demonstrated how the food matrix affects the bioaccessibility of polyphenols during simulated human digestion [9]
Since H.s. polyphenols were previously studied for their colonic fermentation in vivo, focusing on anthocyanins [6], the present study reports on the digestibility of H.s. polyphenols using an in vitro model of human gastric and duodenal digestion [11]
Summary
Hibiscus sabdariffa (H.s.), which belongs to the family of Malvaceae, is commonly known as asroselle, bissap, or karkade. It is widely cultivated in tropical and sub-tropical regions such as India, Mexico, Egypt, and Thailand. The term ‘bioaccessibility’ is defined as the proportion of a nutrient or phytochemical compound ‘released’ from a complex food matrix during digestion and, potentially available for absorption in the upper GIT. In previous studies we evaluated the release of lipids, proteins, and polyphenols during simulated human digestion from natural and blanched skins [8] and demonstrated how the food matrix affects the bioaccessibility of polyphenols during simulated human digestion [9]. The evaluation of the bioaccessibility of pistachio polyphenols, xanthophylls, and tocopherols during simulated human digestion demonstrated that a high percentage of polyphenols were released in the gastric phase, whereas the presence of a food matrix (muffin) decreased the bioaccessibility of protocatechuic acid and luteolin [10]
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