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Phenolic compounds constitute a large and diverse group of secondary metabolites derived from phenylalanine and tyrosine and are widely distributed throughout the plant kingdom. They could be divided into different classes such as simple phenol, phenyl acetic acid, hydroxybenzoic acid, hydroxycinnamic acid, and other phenylpropanoids as well as condensed tannins (proanthocyanidins) and hydrolysable tannins, among others, depending on their basic carbon skeleton structure. Phenolic compounds in plant-based foods have been suggested to have a number of beneficial health effects including prevention of cancer, cardiovascular disease, diabetes, immune disorders, neurogenerative disease and others. These properties are largely attributable to the antioxidant activity of the phenolic compounds as well as other mechanisms of action. Therefore, nutraceuticals of plant origin may evolve to be considered a vital aspect of dietary-disease preventive food components. Agri-food industries generate substantial quantities of phenolic rich by-products, which could serve as an attractive and commercially viable source of nutraceuticals. This contribution mainly summarizes the occurrence of phenolic compounds and some other bioactives in various Agri-food by-products, their bioavailability and health benefits.

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Resveratrol (R), a polyphenol, was structurally modified via esterification with selected fatty acids to expand its potential application in lipophilic foods, drugs, and cosmetics. The esterification was carried out using 12 different fatty acids with varying chain lengths and degrees of unsaturation (C3:0-C22:6). Two monoesters, two diesters, and one triester were identified by high-performance liquid chromatography-mass spectrometry, and the monoesters (R-3-O-monodocosahexaenoate and R-4'-O-monodocosahexaenoate) were structurally confirmed by nuclear magnetic resonance. The lipophilicity of resveratrol and its alkyl esters was calculated using ALOGPS 2.1. Resveratrol exhibited greater antioxidant activity in both 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging assays. Resveratrol esters with long-chain fatty acids (C18:0 and C18:1) showed higher antioxidant activity in the DPPH radical scavenging assay, whereas short-chain fatty acid (C3:0, C4:0, and C6:0) showed higher antioxidant activity in the ABTS radical cation scavenging assay. The results may imply that resveratrol derivatives could be used in lipophilic media as health beneficial antioxidants.

Quercetin, a polyphenolic compound, is widely distributed in plants and has numerous health benefits. However, its hydrophilicity can compromise its use in lipophilic systems. For this reason, quercetin was esterified with 12 different fatty acids as their acyl chlorides with varying chain lengths and degrees of unsaturation. Two monoesters (Q-3′-O-monoester and Q-3-O-monoester) and four diesters (Q-7,3′-O-diester, Q-3′,4′-O-diester, Q-3,3′-O-diester, and Q-3,4′-O-diester) were the major products as was shown by HPLC-MS and 1 H-NMR data. The lipophilicity of quercetin derivatives was calculated; this was found to increase with fatty acid chain length. The antioxidant potential of quercetin and its derivatives was evaluated by using DPPH radical and ABTS radical cation scavenging activity; quercetin showed the highest radical scavenging activity among all tested samples. Despite the decrease of antioxidant activity in this study, the derivatives may show better antioxidant activity in lipophilic media and display improved absorption and bioavailability in the body once consumed.

This work aimed to characterize the phenolic composition and in vitro antioxidant and antiproliferative properties of lyophilized camu-camu (Myrciaria dubia) seed extract (LCE), and to assess the effects of LCE on the antioxidant and sensory traits of yogurt. The LCE contained 46.3% (wt/wt) total phenolic content; the main compounds quantified were vescalagin, castalagin, gallic acid, procyanidin A2, and (−)-epicatechin. The LCE had antioxidant activity, as measured by different chemical assays (2,2-diphenyl-1-picrylhydrazyl, Folin-Ciocalteu reducing capacity, total reducing capacity, ferric reducing antioxidant power, and Cu 2+ chelating capacity), and inhibited the cell proliferation of HepG2 cells (human hepatoma carcinoma; IC 50 = 1,116 µg/ mL) and Caco-2 cells (human colorectal adenocarcinoma epithelial cells; IC 50 = 608.5 µg/mL). In addition, LCE inhibited the in vitro activity of α-amylase, α-glucosidase, and angiotensin-converting enzyme, and protected DNA from peroxyl radical-induced scission. When added to yogurts, different concentrations of LCE (0, 0.25, 0.5, 0.75, and 1.0 g/100 g) increased the chemical antioxidant and reducing capacities. The camu-camu yogurt containing LCE at 0.25 g/100 g had an acceptance index of 84%, showing that camu-camu seed extract may be a potential ingredient for addition to yogurts.

Flavor is an important aspect of both traditional as well as functional food acceptability and can be favorable or unfavorable depending on the chemical nature of the volatile compounds present, their potency, and the presence of non-volatile components. Lipid, as a major food component, contributes to the food flavor formation via both interactions with other components and/or due to its own degradation during food processing, cooking, and storage. This is particularly important when dealing with functional foods that may contain a high proportion of highly unsaturated oils. Lipid may be involved in the Strecker degradation and Maillard reaction, which occurs during food processing, and as a result, it forms a myriad of volatile compounds. Lipoxygenases and autoxidation of unsaturated fatty acids also play an important role in the development of volatile compounds as well as the storage conditions of oils under display lights in the supermarkets, if kept in clear bottles. In this contribution, a cursory account of the role of lipids in flavor formation is provided.

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