In situ oxidation of canola meal sinapic acid by horseradish peroxidase (type II) and tyrosinase

Abstract

The enzymatic oxidation of sinapic acid catalyzed by horseradish peroxidase (HRP) or tyrosinase was investigated using model systems, which contained the pure compound or canola meal. Spectrophotometric scanning of pure sinapic acid solution in the presence of HRP (0.2 U) or tyrosinase (40.3 U) showed continuous decreases in absorbance at 304 nm over a period of 90 and 60 min, respectively. HPLC analyses of enzymatic end products, obtained by the catalysis with HRP or tyrosinase, indicated the presence of two main compounds (1 and 2). After alkaline hydrolysis of canola meal, sinapic acid that was released from sinapine was also converted to compounds 1 and 2 by HRP or tyrosinase. Enzyme reaction kinetics results indicate that the catalytic efficiency (CE = 0.538), reaction velocity (Vmax = 5.67 ∆A/h), and Michaelis‐Menten constant (Km = 926.64 µM) of HRP are significantly higher than those of tyrosinase (CE = 0.041, Vmax = 0.41 ∆A/h, Km = 173.03 µM) at 50–250 μM pure sinapic acid concentrations. Practical applications Canola meal contains a large amount of sinapine, which is the choline ester of sinapic acid, a strong antioxidant compound. However, the oxidation or decarboxylation products of sinapic acid could add value by increasing the level of electron‐dense carboxylic and carbonyl compounds. In this study, enzymatic treatment of alkaline‐hydrolyzed canola meal with horseradish peroxidase (HRP) and tyrosinase was investigated and shown to be suitable for converting sinapic acid into oxidized compounds. Therefore, the enzymatic treatment is a potential application for value‐added processing of canola meal.

Phenolics of mustard seeds: A review on composition, processing effect and their bioactvities

“…A study by Cao et al (2019) investigated the enzymatic oxidation of sinapic acid catalyzed by horseradish peroxidase and tyrosinase. Although no canolol was detected, the result confirmed a potential oxidized effect of tyrosinase on sinapic acid, and sinapine.…”

“…Enzyme‐assisted extraction (EAE) is one of these alternative methods that have an inherent ability to catalyze a reaction with exquisite specificity and the ability to function properly under mild processing conditions (Shahidi et al, 2016). Unlike temperature or pH adjustment, EAE requires moderate extraction conditions with a minimal number and concentration of substances involved and produces more potential as long as less deterioration of finished products (Cao et al, 2019). Usually, enzymes perform as phenolic release agents by digesting hemicellulose, cellulose, pectin, and proteins in plant cell wall matrix (Heemann et al, 2019).…”

“…Tyrosinase is one of the polyphenol oxidases that catalyze the oxidation of monophenols and diphenols without any additional co‐factors. A study by Cao et al (2019) investigated the enzymatic oxidation of sinapic acid catalyzed by horseradish peroxidase and tyrosinase. Although no canolol was detected, the result confirmed a potential oxidized effect of tyrosinase on sinapic acid, and sinapine.…”

“…Nandasiri, Imran, et al (2021) further enhanced the extraction of sinapine, sinapic acid and canolol. This study adopted a new technique RapidOxy® 100, a compact system with built‐in pressurized heating chambers, as a solvent‐free pre‐treatment for producing canolol from residual meals, resulting in the maximum recovery of canolol at 160°C for 10 min (Cao et al, 2019; Nandasiri, Imran, et al, 2021).…”