Sucrose in plant tissue is hydrolyzed to glucose and fructose in boiling water bath under acidic conditions. 5-hydroxymethyl furfural was synthesized from fructose under acid condition and measure the ultraviolet absorption of 5-hydroxymethyl furfural. Glucose must be dissimilated into ketose structure and reduced to obtain 5-hydroxymethylfurfural, but the rate of isomerization of glucose to ketose is very slow. Therefore, the ultraviolet absorption of glucose is much smaller than fructose.
Sucrose can be hydrolyzed by sucrase to produce glucose under acidic conditions, which is catalyzed by glucose oxidase to produce hydrogen peroxide. In the presence of HRP (horse radish peroxidase), hydrogen peroxide reacts with the fluorescent probe to form red fluorescent substance. The sucrose content can be calculated by measuring the fluorescence intensity at the excitation wavelength of 535 nm and the emission wavelength of 590 nm.
Sucrose synthase-Ⅱ (SS-Ⅱ) catalyzes the reaction of substrate to produce sucrose, which reacts with chromogenic agents to produce chromogenic substances. The characteristic absorption peak at 480 nm is found, and the enzyme activity is proportional to the color.
Sucrose synthase-I (SS- I) catalyzes the substrate reaction to generate reducing sugar. The reducing sugar can show color changes when reacting with the chromogenic agent. There is a characteristic absorption peak at 540 nm. The activity of the enzyme is directly proportional to the absorbance.
The chromogenic agent can be catalyzed by acid phosphatase to produce p-nitrophenol in acidic condition. P-nitrophenol has a maximum absorption at 405 nm. The activity of TRAP can be calculated by measuring the amount of produced p-nitrophenol. The activity of acid phosphatase being detected in the presence of tartric acid is regarded as TRAP activity.
TBARS and TBA can react under high temperature and acid conditions and then form a pink compound, the concentration of which is linearly related to the concentration of TBARS in the sample. The TBARS concentration can be calculated by measuring the OD values at 530-540 nm.
TBARS and TBA can react under high temperature and acid conditions and then form a pink compound, the concentration of which is linearly related to the concentration of TBARS in the sample. The TBARS concentration can be calculated by measuring the fluorescence values at the excitation wavelength of 530 nm and the emission wavelength of 550 nm.
Thioredoxin system, as one of the most important antioxidant systems in the body, can stabilize the redox balance of organisms, regulate signal transduction. It is also related to cell REDOX reaction, nucleic acid metabolism, cell growth and tumorigenesis. Thioredoxin reductase (TrxR) is a NADPH-dependent dimer selenase containing the flavin adenine dinucleotide (FAD) domain and is a member of the pyridine nucleotide-disulfide oxidoreductase family. The thioredoxin system consists of NADPH, thioredoxin reductase and thioredoxin. The TrxR catalytic substrate makes the reducing agent reduce the color developer with a characteristic absorption peak at 412 nm.
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