Recovery of Antimicrobials and Bioaccessible Isoflavones and Phenolics from Soybean (Glycine max) Meal by Aqueous Extraction

Abstract

Soybeans display strategic potential in food security as a source of protein and functional bioactives for human consumption. Polyphenols and other bioactive compounds can be recovered after an aqueous extraction from soybean meal, a byproduct of soy oil refining. The objective of the present study was to compile and quantify compounds from soybean oil refinery by-products, providing information about valuable bioactive phytochemicals, their bioaccessibility and potential bioactivities. Genistin, daidzin, glycitin and malonylgenistin were the predominant isoflavones, and the overall bioaccessibility of their glycosidic forms was of nearly 75%. Sixteen phenolics were identified and caffeic acid, 5-caffeoylquinic chlorogenic acid and hesperidin were the most predominant. Approximately 30% of gallic acid, syringic acid, vanillic acid and myricetin were released and the antioxidant capacity of aqueous extract was enhanced after simulated in vitro gastro intestinal digestion. The ability of aqueous soybean meal extract to inhibit lipid peroxidation was higher than natural and synthetic food antioxidants. Antimicrobial activity against several foodborne pathogens and antitumoral activity towards human glioblastoma cell line were also observed, but the aqueous extract showed no cytotoxicity to healthy murine cells. Compounds derived from the aqueous soybean meal extract have the potential to be used as health promoting agents.

Bioactive Phenolic Compounds From Agri-Food Wastes: An Update on Green and Sustainable Extraction Methodologies

“…The olive oil industry also generates high amounts of byproducts, which are particularly rich in lignans, secoiridoids, and especially hydroxytyrosol, which is one of the most bioactive phenolic compounds present in nature, endowed with anti-inflammatory and antiplatelet properties (12,(28)(29)(30)32) (Figure 1). Soybean (33) and palm oil (34) byproducts have been also described as a valuable source of polyphenols.…”

Evaluating the In Vitro Potential of Natural Extracts to Protect Lipids from Oxidative Damage

“…For in vitro systems where no chemical oxidizing agent is added, but LPO occurs through different pathways, lipid peroxides thus formed become the main oxidizing compounds in the medium, and LPO can be quantified by using a reagent prone to be oxidized by lipid peroxides (amount of reagent lost can be converted in amount of lipid peroxides). This is the case of the thiocyanate method [68], which has been used to track LPO in lipid-solution-based LPIP assays (as described in the next section) [69][70][71][72][73][74][75][76][77][78]. Given the lack of an oxidizing trigger in these assays, the capacity of the medium to oxidize iron (II) to iron (III) is directly proportional to the concentration of lipid peroxides.…”

“…Importantly, one should note that quantifying the lipid peroxides of a sample is a measure of LPO that will decay along time, as lipid peroxides degrade into smaller molecules; thus, it is a measure of "early lipid peroxidation". In the thiocyanate method, ferrous ions are oxidized into ferric ions, which in turn form a colored complex with thiocyanate (ferric thiocyanate), with maximum absorbance at 485 nm [68][69][70][75][76][77].…”

“…Emulsification of LA in PB 20 mM pH 7, using Tween-20 (5.6 µg/mL LA and 5.6 µg/mL Tween-20) Mixture of emulsion in PB, water and sample dissolved in 80% methanol [70] Dissolution of LA (8 mM) in Borate buffer 50 mM pH 9 Mixture of previous solution with FeSO 4 , EDTA, H 2 O 2 , sample dissolved in methanol and PB 0.4 M pH 6.75 [126] Dissolution of sodium linoleate in water (16 mM) Mixture of previous solution in PB 50 mM pH 7.4 [127] Dissolution of LA in ethanol, 2.5% (v/v) Mixture of previous solution with distilled water, PB 50 mM pH 7 and sample [74] Ethanol Dissolution of LA (1.3% (v/v)) and NP in ethanol:water 3:1 (v/v) [76] Different methods available to disperse linoleic acid in a medium that is compatible with oxidizing conditions allow the adaptation of the medium for NP dissolution. For instance, the work of Freitas et al [76] used a system mostly composed of ethanol, which might allow the LPIP determination of a wider range of NPs (including some less polar extracts) using water-soluble radical initiators (such as AAPH) or transition metals. In more aqueous systems, the use of saponified linoleic acid (the sodium salt, for instance) to increase water solubility, with [70,73,128] or without [70,126] the addition of a surfactant, might be a solution to test very hydrophilic compounds (such as natural polysaccharides), which are insoluble, even at low concentrations of organic solvents.…”

“…Thus, lipid peroxidation can be detected by using methods that rely on oxidation themselves, since the lipid peroxides will act on the reagents and cause their oxidative state to increase, developing color. For this reason, linoleic-acid-based systems have often been used as LPO quantification method in the thiocyanate-iron(III) complex spectrophotometric assay [69][70][71][72][73][74][75][76][77][78], which is an advantage of using this substrate given the increased simplicity and decreased interferences of this method.…”