Sinapic acid Phenolic compound

Landete and others (2009) reported that Lactobacillus plantarum have the ability to metabolize phenolic compounds found in olive products (such as oleuropein, hydroxytyrosol, and tyrosol, as well as vanillic, p-hydroxybenzoic, sinapic, syringic, protocatechuic, and cinnamic acids). For example, oleuropein was metabolized mainly to hydroxytyrosol, whereas protocatechuic acid was decarboxylated to catechol by the enzymatic actions. 

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. 

Later, Tressl et al. (1976) also proceeded to the thermic degradation (2 h, 200 JC) of ferulic acid (H.87) and identified the same phenols as Fiddler et al., plus 4-isopropylguaiacol and vanillin alcohol (4-hydroxy-3-methoxybenzenemethanol) which have not been found in coffee. For isoeugenol (H.38), the formula is written as the (E)-( trans -) isomer, but nothing was specified in the text. Tressl et al. (1976) also published the results of thermal decomposition of cinnamic, p-coumaric (H.84) and sinapic (H.90) acids. Many of the simple phenols (and other aromatic compounds) formed have also been identified in roasted coffee volatiles. A thermic fragmentation of quinic acid (E.62) has shown that simple acids, phenols and polyphenols originate from this precursor (Tressl et al., 1978a). 

Except perhaps for caffeic acid (H.86), these acids were mainly identified after hydrolysis of extracts, which means after degradation of the chlorogenic acids, CGA (See Section 2.1.4). In commercial roasted coffee, Hughes and Thorpe (1987) identified, by comparison with standard compounds, coumaric acid (without specification, probably p-), isoferulic acid (H.88) but surprisingly not ferulic acid (H.87), caffeic acid (H.86) and its dimethyl ether (H.89) as well as sinapic acid (H.90). They used capillary GC for the separation and identification of these phenolic acids and other carboxylic acids. The cinnamic acids are generally linked to quinic acid, but in robusta coffee caffeic and /j-coumaric (H.84) acids have also been identified as derivatives of tryptophan (see Section 2.1.2) (Morishita et al., 1987 Murata et ah, 1995) and... 

Other phenolic compounds are in soybeans, mainly acids, such as chlorogenic, isochlorogenic, caffeic, ferulic, -coumaric, syringic, vanillic, -hydroxybenoic, salicylic, and sinapic acids. Some of these acids have strong antioxidant activity (White Xing, 1997). 

Sinapine, a choline ester of sinapic acid (Figure 10 was identified in yellow, brown, and oriental mustard Tins compound, 3,5-dimethoxy hydroxy cinnamoy) choline, is common in the Brassica group Researchers have shown that although sinapine is the positive ion to sinalbin, the glucosinolatc and phenolic choline ester contents are not correlated with one another (7). For this reason sinapine is seen in both brown... 

The phenolic acid content of vegetables of the genus Brassica consists almost totally of hydroxycinnamic acid compounds, of which, unlike in other species of vegetables, sinapic acid is the predominant one [55] (Table 3). 

The principal phenolic acids in these vegetables are ferulic and p-coumaric acid derivatives, the green parts of chives and leeks containing more than in the white part. In leek, the white tissue contains 6-7 mg ferulic acid per kg f.w., while this compound reaches concentrations of 23-39 mg/kg in the green parts [64]. In the case of chive, p-coumaric acid derivatives reach 21-51 mg/kg and ferulic acid derivatives 32-76 mg/kg. In garlic a different pattern of phenolic metabolite accumulation is observed in skins and internal tissues. The external tissues contain 49-58 mg/kg p-coumaric acid, 27-31 mg/kg ferulic acid and 27-25 mg/kg sinapic acid, whereas the internal tissues only contain 2mg, 6-8 mg and 2 mg/kg, respectively. In addition, the internal tissues contain 12-13 mg/kg p-hydroxybenzoic acid [64]. 

The effects of a series of phenolic compounds in artificial diets on biotype B greenbugs (Schizaphis graminum) has been evaluated (Levin, 1976, Todd et al., 1971). Z-Caffeic acid (but not -caffeic acid) caused a drastic reduction in growth and inhibited reproduction. Less than 20% of the greenbugs survived on diets that contained vanillic, sinapic, gentisic, or femlic acids (Todd et al., 1971). 

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.

Ginkgo biloba leaves were extracted and characterized by their phenolic acid profile (protocatechuic, p-hydroxybenzoic, vanillic, cafieic, isovanillic, cis- and trans-p-coutmaic, cis- and Ouns-fenilic, sinapic acid). A C g column (A = 254 nm) and a 73/35 water/methanol mobile phase were used to elute all compounds in 30 min. In general, peak shapes were good, as was overall resolution [403]. 

Phenolic compounds are widely distributed in plant parts from the roots to the seeds and include phenolic acids, flavo-noids and tannins. The tannins may reduce protein digestibility (Ford and Hewitt, 1979) and perhaps the bioavailability of other nutrients. The flavonoids have been reported to have a number of nutritional and pharmacological activities (Kuhnau, 1976). Phenolic acids include benzoic and cinnamic acid derivatives. The benzoic acid derivatives include p-hydroxy-benzoic, protochate-chuic, vanillic, gallic and syringic acids. The cinnamic acids, p-coumaric, caffeic, ferulic and sinapic are found in most oilseeds used to prepare protein concentrates and frequently occur in the form of esters with quinic acid or sugars. Chlorogenic acid for example is an ester of caffeic acid and quinic acid and is found in several isomeric and derivatized forms. 

Higher plants accumulate a wide range of phenolic compounds that are derivatives or metabolites of cinnamic acid. The phenyl-propanes, generally denoted as C -C compounds, are important intermediates in the biosynthesis of lignin and flavonoids. The common phenylpropane derivatives cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid, 5-hydroxyferulic acid, and sinapic acid, are interrelated and are synthesized from phenylalanine (Fig. 5). 

Fig. 2a All seven Semen Sinapis methanol extracts show in VIS 4 -5 dark blue zones with Sinalbin at =0.58 (Tl) partly overlapped with sinigrin which in Sinapis alba is contained only in low concentration. In Sinapis nigra it is reported to be the dominant compound. The blue zone at ] =0.24 might be identical with sinapin the choline derivative of Sinapic acid (see also Fig. 2b). The blue zones in the front zone (I =0.85 - 0.95) might be Sinapic acid and phenol carboxylic acid derivatives.

Biosynthesis of Plant Phenoiics. Phenolic compounds in plant foods are secondary metabolites which are derived from phenylalanine, and in some plants from tyrosine via enzymatic deamination assisted by ammonia lyase (Figure 1). Phenylpropanoids, the first products of deamination of phenylalanine and/or tyrosine consist of a phenyl ring (C ) and a 3 carbon side chain (C,). These Q-C, compounds may subsequently undergo hydroxylation in the phenyl ring and possibly subsequent methylation. This would lead to the formation of a large number of products which include cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid and sinapic acid (5). 

Hydroxycinnamic acids (HCAs) are a major class of phenolic compounds found in nature. They are secondary metabolites derived from tyrosine and phenylalanine, which have a C6-C3 carbon skeleton with a double bond in the side chain that may have a trans or cis configuration (Figure 3.11) [55]. Among the most common and well known HCAs are cinnamic acid, caffeic acid, ferulic acid, m-coumaric acid, o-coumaric acid, p-coumaric acid, 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). 

Sinapic acid, an important hydroxydnnamic acid is the most significant phenolic compound in rapeseed and forms 70.2-85.4% of free phenolic adds in defatted canola meals. Esterified forms of these phenolic acids constitnte abont 99% of total phenolics in rapeseed flour of which the sinapine, the choline ester of sinapic acid, is the main ester. A phenolic glucoside namely glucopyranosyl sinapate is also reported in canola (Amarowicz and Shahidi, 1994). Figure 2.1 shows the structures of sinapic acid, sinapine and glucopyranosyl sinapate. 

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