# Phenolic Compound Composition and Biological Activities of Fractionated Soybean Pod Extract
## 3 Results and Discussion  
Qualitative analysis of the phenolic compounds from fractionated soybean pod extracts was conducted using UPLC-ESI-QTOF-MS in positive ionization mode. Putative identification of compounds present in the extracts and fractions with variable lipophilicity was made on the basis of their \(m/z\) value and MS spectral data obtained with Agilent MassHunter data acquisition software, Personal Compound Database and Library (PCDL) software and available online databases (MassBank, PubChem), as shown in Table 1. In total, 50 different phenolic compounds were tentatively characterized in soybean pod extract. These compounds can be grouped into three different chemical families: phenolic acids, flavonoids and other polyphenols, as mentioned in Table 1. In the available literature there are no reported results on the qualitative composition of polyphenols in soybean pods; this is the first investigation to analyze polyphenic composition in agricultural soybean waste. The largest number of compounds detected in the soybean pod extracts and fractions with variable lipophilicity were from the class of flavonoids. Identified subgroups of flavonoids included isoflavuoids, flavanols, flavones, flavonoids and chalconids. Most of the detected flavonoids were of glycoside forms. One of the most important groups of phenolic compounds present in the studied soybean pod extracts and fractions are isoflav, which have well documented health-promoting properties. They can be divided into three groups in soybeans on the basis of their aglycone moiety, namely daidzein, genistein and glycitein. In each group, four different forms are present: malonylglucoside, acetylglucose, glucoside (daidzin, genistin, glycitin) and aglycone [10,23]. Aglyconesand glucosides were previously identified as the major group of phenolic compounds in soybean pods [24; 25]. In the present study, all 12 isoflavnes were tentatively identified. Among the isoflavoids, we also identified 2\({}^{\prime}\)-hydroxyformonentin. This compound has been previously described in soybean leaves [26]. Another group of polyphenols identified in soybean pod extract was flavones. Among these, apigenin, luteolin and their derivatives were identified, which is in accordance with previous research [27; 28]. [PERSON] et al. [27] were the first to identify these compounds in soybean pods. In this flavonoid subclass we also tentatively identified chrysin (5,7-dihydroxyflavon), which was also previously described in soybean leaves [26; 29]. The flavonols quercetin, quercetin 3-\(O\)-glucose, dihydroquercetin 3-\(O\)-Hammoside, dihydroquercetin (taxifolia) and the flavanone naringenin were also tentatively identified in the studied soybean pod extracts. Quercetin derivatives were previously reported by [PERSON] et al. [24] in soybean pod extract. The naringenin was synthesized from \(p\)-coumaroylCoA, which is derived from \(p\)-coumaric acid. This compound has been considered as a central intermediate in the production of different flavonoids including apigenin and genistein [8]. This fact could explain the presence of these flavonoids in the extract. The flavanols (+)-catechin/(-)-epicatechin and 3\({}^{\prime}\)-O-methylcatechin and the chal-conoids phloridzin and 3-hydroxyphloridzin were found in soybean pod extract for the first time and putatively identified. These compounds have already been found in soybean seeds [23; 30; 31], but never in the pods. The last group of phenolic compounds tentatively identified in the studied extracts were phenolic acids. The presence of ferulic acid, \(p\)-coumaric acid and \(p\)-hydroxybenzoic acid were previously reported in the extracts of soybean seeds and flour [30; 32]. Among the phenolic acids we also tentatively identified derivatives of \(p\)-coumaric acid (3-\(p\)-coumaroylqunc acid), ferulic acid (3-feruloquinic acid and ferulic acid 4-\(O\)-glucose) and caffeic acid (3,5-\(O\)-dicaffeoylquinic acid, caffeoylmale acid and dihydrocaffeic acid 3-\(O\)-glucuron).