Sinapic acid phenolic constituents

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). 

FIGURE 15.5 HPLC chromatograms of 70% methanolic extract of rapeseed meal indicating benzoic acid derivatives (a) at 275 nm and sinapic acid derivatives (b) at 330 nm. Chromatographic conditions elution using water/methanol (90 10) with 1.25% O-phosphoric acid as solvent A and methanol (100%) with 0.1% ( -phosphoric acid solvent B in a C-8 Chrospher column (Knauer). Sinapoyl glucose (GP), sinapine (SP), sinapic acid (SA), others non-identified phenolic constituents. 

Fignre 15.6 indicates the ranges of the phenolic constituents of the sinapic acid derivatives detected at 330 nm using HPLC for the commercial rapeseed meal extracts. Commercially available meals of rapeseed and mustard procured from (dennany and... 

The theoretical contribution of the phenolic constituents, such as free sinapic acid, sinapoyl glucose and sinapine, to the total radical scavenging activity of the extracts is shown in Figure 15.11. The concentration of the phenolic constituents was recorded by HPLC (330 nm). Calibration curves for the RSA were recorded using standard compounds. 

FIGURE 15.13 DPPH radicals scavenged with 70% methanolic extract of commercial meals. Right to left mustard Delhi, mustard Manipur, meals X, Y, A (non-specified), husk meal, second-pressed first-pressed solvent-extracted and cold-pressed meals. From the same company. Radicals scavenged by phenolic constituents sinapoyl glucose (SG), sinapine (SP), sinapic acid (SA) and rest from un-identified (non-identified) phenolic constituents. 

Other constituents present in onion include phenolic acids (caffeic, sinapic, p-coumaric, protocatechuic acids, etc.), flavonoids (e.g., quercetin, isorhamnetin, taxifolin, and their glucosides), anthocyanins (e.g., cyanidin, carboxypyranocyanidin, and peonidin glycosides), sterols (cholesterol, stigmasterol, P-sitosterol, etc.), saponins (e.g., trope-osdies and ascalonicosides), sugars,... 

---