Sinapic acid increase

Polyphenolic phytochemicals are classified into three major groups phenolic acids, fla-vonoids, and tannins. Phenolic acids include hydroxybenzoic, hydroxyphenylacetic, and hydroxycinnamic acids (Figure 11.3.3). Hy-droxycinnamic acids are the most widely distributed of the phenolic acids in plant tissues. The important hydroxycinnamic acids are p-coumaric, caffeic, ferulic, and sinapic acids. Most hydroxycinnamic acids are rarely encountered in the free state in nature. They occur as glucose esters and, more frequently, as quinic acid esters (Herrmann, 1989). Phenolic acids are usually detected at wavelengths between 210 and 320 nm. In general, the polarity of phenolic acids is increased mainly by the hy-... 

The phenolic acids of interest here [caffeic acid (3,4-dihydroxycinnamic acid), ferulic acid (4-hydroxy-3-methoxycinnamic acid), p-coumaric acid (p-hydroxycinnamic acid), protocatechuic acid (3,4-dihydroxybenzoic acid), sinapic acid (3,5-dimethoxy-4-hydroxyxinnamic acid), p-hydroxybenzoic acid, syringic acid (4-hydroxy-3,5-methoxybenzoic acid), and vanillic acid (4-hydroxy-3-methoxybenzoic acid)] (Fig. 3.1) all have been identified as potential allelopathic agents.8,32,34 The primary allelopathic effects of these phenolic acids on plant processes are phytotoxic (i.e., inhibitory) they reduce hydraulic conductivity and net nutrient uptake by roots.1 Reduced rates of photosynthesis and carbon allocation to roots, increased abscisic acid levels, and reduced rates of transpiration and leaf expansion appear to be secondary effects. Most of these effects, however, are readily reversible once phenolic acids have been depleted from the rhizosphere and rhizoplane.4,6 Finally, soil solution concentrations of... 

Thermal evaporation brought about an increase of ferulic acid (69), vanillin (39) and syringaldehyde (63) with an attendant drastic decrease in sinapic acid (99). ... 

Storage of bean seeds at high temperature (35 °C) and humidity causes textural defects along with an increase in free phenolic acids (caffeic, p-coumaric, ferulic and sinapic acids), a decrease in soluble esters, and a strong increase in ferulic acid bound to soluble pectins [59]. These modifications result in poor soaking imbibition of seeds and in prolonged cooking time. 

Because of its potent bioactive potential, the increase of canolol content in rape-seed oil would theoretically produce oil with enhanced food value and as well as longer shelf life (Spielmeyer et al, 2009). Canolol is thermally unstable, even though it is being produced from sinapic acid at higher temperatures. An exponential decrease in the canolol content from 81.4 to 11.0 g/g in oil was observed when it is exposed to a heat treatment up to a temperature of 180°C for 20 min. 

Results of the present stndy indicate that the bonnd and the non-fractionated extract could inhibit the hydroperoxides, propanal and hexanal in a similar manner to sinapine alone when compared with the control sample withont any added antioxidant. This was in contrast to the resnlts illustrated in the bnik rapeseed oil system, where these extracts and sinapine fnnctioned as a mild pro-oxidative or ineffective antioxidant. The non-fractionated extract and sinapine represented a comparable manner in inhibiting PV increase, whereas the bound fraction was more effective as compared with sinapine and nonfractionated extract. This means that in this case, the unidentified peaks of the hydrophilic compounds contributed to the enhanced activity of the bound-phenolic fraction. It was also observed that sinapic acid and the free-phenolic fraction functioned in a similar manner until the 18th day of incnbation. 

The stability of anthocyanins is increased by acylation (Dougall et al. 1997). These acylated anthocyanins may occur naturally as in the case of an anthocyanin from the purple yam (Yoshida et al. 1991). This anthocyanin has one sinapic residue attached through a disaccharide and was found to be stable at pH 6.0 compared to other anthocyanins without acylation. Dougall et al. (1977) were able to produce stable anthocyanins by acylation of carrot anthocyanins in cell cultures. They found that a wide range of aromatic acids could be incorporated into the anthocyanin. 

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