Abstract
Fennel (Foeniculum vulgare Mill.) waste contains a broad range of bioactive molecules, including polyphenols, which have poor bioaccessibility during gastrointestinal digestion. This work aimed to investigate the bioaccessibility of total phenolic compounds and the antioxidant capacity during simulated gastrointestinal digestion using two nutraceutical formulations based on non-acid-resistant (NAR) and acid-resistant (AR) capsules containing aqueous-based extracts from fennel waste. Moreover, to obtain a comprehensive investigation of the polyphenolic constituents of the fennel waste extract, a high-resolution mass spectrometry (Q-Orbitrap) analysis was performed. Notably, chlorogenic acids, such as 4-caffeoylquinic acid and 3,4-dicaffeoylquinic acid, were the most detected compounds found in assayed samples (1.949 and 0.490 mg/g, respectively). After in vitro gastrointestinal digestion, the extract contained in AR capsules displayed higher bioaccessibility in both the duodenal and colonic stages (1.96 and 5.19 mg GAE/g, respectively) than NAR capsules (1.72 and 3.50 mg GAE/g, respectively), suggesting that the acidic gastric conditions negatively affected the polyphenol compounds released from the NAR capsules. Therefore, the aqueous extract of fennel waste could be proposed as an innovative and easily available source of dietary polyphenols. Furthermore, the use of an AR capsule could improve the polyphenol bioaccessibility and can be proposed as a nutraceutical formulation.
Highlights
Fennel (Foeniculum vulgare Mill.) is a plant belonging to the Apiaceae family, widely naturalized in many parts of the world and commonly considered as native in the Mediterranean basin [1]
Despite the efforts made in the last decade to find an alternative use for food waste and by-products, fennel waste remains unused as a raw material to produce high value-added products
The most studied compounds of fennel waste are extracted from the volatile fraction, whereas the polyphenolic compounds have been barely evaluated to date [12]
Summary
Fennel (Foeniculum vulgare Mill.) is a plant belonging to the Apiaceae family, widely naturalized in many parts of the world and commonly considered as native in the Mediterranean basin [1]. The use of a simple water-based extraction procedure is recognized as the greenest way to recover bioactive compounds and reduce the environmental impact of agro-industrial wastes [6,7]. Previous scientific investigations suggest that fennel waste contains a wide range of human health-related compounds, including polyphenols [8]. Polyphenols are well-known to exert a broad range of important biological properties able to reduce oxidative stress and inflammation [10]. In this line, a wealth of data from epidemiological studies support an inverse association between polyphenol-rich diets and the incidence of several age-related diseases [11]. Di Donato et al [8] investigated the polyphenolic profile of fennel waste through reverse-phase high-performance liquid chromatography (RP-HPLC)
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