Gallic-sinapic acid

Notes ace, acetic acid oxa, oxalic acid mal, malonic acid sue, succinic acid mly, malic acid hba,/ -OH-benzoic acid gao, gallic (tri-OH-benzoyl) acid cum, / -coumaric acid caf, caffeic acid fer, ferulic acid sin, sinapic acid hca, 3,5-diOHcinnamic acid tar, tartaric acid ara, arabinose xyl, xylose rha, rhamnose gal, galactose glc, glucose glu, glucuronic acid 2-(xyl)glc, sambubiose 2-(xyl)gal, lathyrose 2-(rha)glc, neohesperidose 6-(rha)gal, robinose 6-(rha)glc, rutinose 2-(glc)glc, sophorose 3-(glc)glc, laminariobiose 6-(glc)glc, gentiobiose. 

Some researchers have investigated the potential of hazelnuts as a source of natural antioxidants. Yurttas et al. (32) assessed the phenolic composition of metha-nolic extracts of hazelnuts, showing that gallic acid, p-hydroxl benzoic acid, caffeic acid, and sinapic acid were the predominant phenolic acids reported. In addition, quercetin and epicatechins were present. The composition of phenolic acid constituents in hazelnut meal has also been assessed by Senter et al. (14) (Table 2). 

Phenolic acids include the benzoic acids (Ce-Ci), e.g., gallic, vanillic, syringic, protocatechuic, p-hydroxy-benzoic acid, as well as cinnamic acids (C6-C3), e.g., caffeic, p-coumaric, ferulic, sinapic acids, and their dep-sides and derivates, e.g., rosmarinic acid and lithospermic acid (Fig. 1). Phenolic acids and flavonoids in plants may occur in the free form, but they are often glycosylated with various sugars, especially glucose. Phenolic acids may also be present in the esterified as well as bound forms. Free phenolic acids are found especially in herbs and spices and, very often, in compounds responsible for antioxidant activity (benzoic and cinnamic acids and some of their derivatives). The bound forms are more common for the fruits, vegetables, and other plant materials. Therefore, in some cases, it is necessary to combine the analysis of their free and bound forms. 

Fig. 3 HPLC analysis of phenolic acids using (a) Separon SGX Cig column and (b) Symmetry Cig column and gradient elution. Conditions (A) column Separon SGX Cig (250 x 4.6 mm, 7 pm), mobile phase methanol-water (pH = 2.5, adjusted with formic acid), linear gradient from 15% methanol to 75% methanol in 40 min, flow-rate 0.5 mL/min (B) column Symmetry Cig (150 x 3.9 nm, 5 pm), mobile phase and flow-rate same as in (a). Peaks 1) gallic acid, 2) protocatechuic acid, 3) catechin, 4) caffeic acid, 5) sinapic acid, 6) rosmarinic acid.

GALLIC ACID SINAPIC ACID FERULIC ACID... 

Five soluble phenolic acids (free and esterifled), one of which is a hydroxylated derivative of benzoic acid (gallic acid) and four are cinnamic acid derivatives (caffeic, p-coumaric, ferulic, and sinapic acids), have been studied and tentatively identified in ethanolic extracts of hazelnut kernel and hazelnut by-products (Table 13.2) [31]. The order of total phenolic acid concentration was as follows hazelnut hard shell > hazelnut green leafy cover > hazelnut tree leaf > hazelnut skin > hazelnut kernel. Different phenolic acids predominate in each plant part examined. Among the identified phenolic acids, p-conmaric acid was most abundant in hazelnut kernel, hazelnut green leafy cover, and hazelnut tree leaf, whereas gallic acid was most abundant in hazelnut skin and hazelnut hard shell, possibly implying the presence and perhaps the dominance of tannins in the latter samples (Table 13.2). The same number, but different concentration, of phenolic acids have also been reported in hazelnnt kernel and hazelnut green leafy cover [30]. 

Yurttas et al. [26] isolated and tentatively identified six phenolic aglycones in Turkish and American hazelnut extracts these were gallic acid, p-hydroxybenzoic acid, epicatechin and/or caffeic acid, sinapic acid, and quercetin. However, the variety of hazelnut and extraction solvents used by Shahidi et al. [31] was different from that used by Yurttas et al. [26]. Variety and extraction exert a great influence on the concentration and variability of phenoUc acids present. Recently, Amaral et al. [29] identified and quantified four phenolic acids, namely 3-cafifeoylquinic, 5-caffeoylquinic, caffeoyltartaric, and p-coumaroyltartaric acids, in hazelnut leaves from 10 different cultivars grown in Portugal. Like hazelnut, some of the other tree nuts and their processing by-products have been reported to contain different patterns and levels of phenolic acids [3]. 

Fig. 4 High-pressure fast gradient separation of natural phenolic antioxidants, (a) Ascentis Express CIS column with fused core 2.7 Jtm CIS particles with a thin porous outer shell (0.5 p.m), 30 X 3.0 mm I.D. at 1.5 ml/min, 53 MPa. (b) Acquity BEH Phenyl column with totally porous particles in 1.7 Jtm particles at 1.5 ml/min, 74 MPa, UV detection, 254 nm. Sample 1, gallic acid 2, protocatechine 3, esculine 4, chlorogenic acid 5, caffeine 6, epicatechine 7, vanilline S, rutine 9, sinapic acid 10, hesper-idine 11,4-hydroxycoumarine 12, morine 13, quercetine 14, 7-hydroxyflavone.

Fig. 6 Comprehensive LC x LC separation of phenolic acids and flavones using parallel gradients in the first and in the second dimension, (a) Instrumental setup (h) parallel gradients in the first (D1) and in the second (D2) dimensions (c) contour plot and (d) 3-D presentations of 2-D chromatograms, UV detection at 280 nm. D2 pressure = 400 har. Compounds 1, esculine 2, 4-hydroxyphenylacetic acid 3, chlorogenic acid 4, gallic acid 5, protocatechuic acid 6, syringic acid 7, vanillic acid 8, salicylic acid 9, hesperidine 10, p-hydroxyhenzoic acid 11, sinapic acid 12, (-)-epicatechine 13, naringin 14, caffeic acid 15, ferulic acid 16, (-l-)-catechin 17, 4-hydroxycoumarin 18, p-coumaric acid 19, rutine 20, flavone 21, 7-hydroxyflavone 22, hesperetin 23, naringenin 24, luteolin 25, apigenin 26, quercetin 27, hiochanin A.

X 3.9 nm, 5 xm), mobile phase and flow-rate same as in (a). Peaks 1) gallic acid, 2) proto-catechuic acid, 3) catechin, 4) caffeic acid, 5) sinapic acid, 6) rosmarinic acid. 

The base peak of sinapic acid and ferulic acid is produced by similar pattern of fragmentation. A [M-117] peak is generated for gallic, caffeic, and protocatechuic acids on fragmentation. Chemical ionization (Cl) is also employed in some GC-MS systems where an electron beam is used to ionize a gas (methane or ammonia), which subsequently ionizes the analyte. This method gives more prominence to the molecular ion and results in less ionization. 

Fig. 66.4 Representative MALDI-TOF MS spectra of phenolic acids. MALDI-TOF MS spectra of phenolic acids are marked as number (a) ferulic acid, (b) syiingic acid, (c) cinnamic acid, (d) gallic acid, (e) caffeic acid, (f) p-coumaric acid, (g) sinapic acid, (h) dihydroxybenzoic acid...

Fig. 5 In vitro grafting of gallic acid onto cafeic and sinapic acid...

Phenolic acids are related compounds (aromatic carboxylic acids), divided into hydroxycinnamic and hydroxybenzoic acids. Hydroxycinnamic acids are more common and they mainly include gallic acid, p-coumaric, caffeic, chlorogenic acid, ferulic and sinapic acids. 

Phenolic acids also constitute an important class of phenolic compounds with bioactive functions like the flavonoids, usually found in plant and food products. According to their structure, phenolic acids can be divided in two subgroups the hydroxybenzoic and the hydroxycinnamic acids. The most commonly found hydroxybenzoic acids include gallic, p-hydroxybenzoic, protocatechuic, vanillic and syringic acids caffeic, ferulic, p-coumaric, and sinapic acids are classed in the hydroxycinnamic acids (Bravo, 1998 Martins et al., 2011). 

Ceto et al. Tyrosinase and laccase Voltammetric Fetulic acid/ 50 pM Gallic acid/50 pM Sinapic acid/50 pM Beer [65]... 

Genistin, genistein, daidzin, daidzein, glycitin, glycitein, ononin, sissotrin, formononetin, and biochanin A, gallic, protocatechuic, j9-hydroxybenzoic, vanillic, caffeic, syringic, j -coumaric, ferulic, sinapic acid... 

Advances in analytical procedures resulted in several reports on anthocyanins acy-lated with hydroxycinnamic acids (p-coumaric, caffeic, ferulic, sinapic, and 3,5-dihydroxycinnamic acids), hydroxybenzoic acids (p-hydroxybenzoic and gallic acids), and aliphatic acids (malonic, acetic, malic, oxalic, succinic and tartaric acids). However, not all of them were found in anthocyanins isolated from foods. Among the 44 fruits listed in Table 4.3.1, 15 presented acylated anthocyanins as did 12 of 13 vegetables shown in Table 4.3.3 and 2 of the 9 grains cited in Table 4.3.4. On the other hand, acylated anthocyanins were found in all grapes from Vitis species, although at different abundance levels, as can be seen in Table 4.3.2. A higher... 

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