Study on Black Rice Extract Anthocyanin Anti Fatigue

Black rice is a precious rice variety in China and was once considered a tribute product. It is not only rich in protein, essential amino acids, manganese, zinc, iron and other trace elements, but also contains black rice anthocyanins in the black rice bran. Studies have shown that black rice extract is a flavonoid pigment that is a type of anthocyanin, with a content of 6.4 g/100 g², and has strong free radical scavenging and antioxidant properties (13-5). It is a natural food coloring resource with health benefits. The health benefits of black rice extract have become one of the hotspots of nutritional and health research today. However, research on the application of black rice extract in the field of sports is currently lacking. With the in-depth research of sports scientists, the application of black rice anthocyanin (flavonoids) as a functional factor to delay fatigue and promote fatigue recovery in the development of sports nutrition supplements is of great theoretical and practical significance. This paper mainly analyzes and discusses the anti-fatigue biochemical mechanism of black rice extract on the basis of reviewing a large amount of relevant data, laying a foundation for the subsequent development of black rice extract sports nutrition supplements, and also providing a reference for the further development of black rice anthocyanin.

1 The free radical-lipid peroxidation mechanism of exercise-induced fatigue

Exercise-induced fatigue refers to “the body's physiological processes being unable to maintain its functions at a certain level or the organs being unable to maintain a predetermined exercise intensity”. This is the description of exercise-induced fatigue given at the Fifth International Congress of Sports Biochemistry in 1982. Since then, research into the mechanism of exercise-induced fatigue has been a topic of great interest to scholars from all over the world, but there is still no definite conclusion. What is clear is that the main causes of fatigue during prolonged, high-intensity work or exercise are the large consumption of energy substances in the body, the large accumulation of the metabolic product lactic acid, which causes a drop in pH, and the increase in free radicals. During exercise, the production of free radicals increases. With appropriate exercise training, the body undergoes adaptive changes, which bring the production and removal of free radicals into balance and prevent damage to the body. However, this adaptive change in the body is only relative. If the intensity or duration of exercise is too high, the increase in free radicals will still cause damage to tissues and lead to exercise fatigue.

Possible causes of increased free radicals during exercise include: a. Mitochondrial electron transport chain: During exercise, the body's metabolic level increases, energy consumption increases, and ATP resynthesis is accelerated to meet the body's metabolic needs. Mitochondrial oxidative phosphorylation is enhanced, which produces uric acid under the action of free enzymes during the mitochondrial electron transport process, and also produces free radicals, which intensify lipid peroxidation; b. A relative decline in the activity of antioxidant enzymes: During high-intensity exercise, the body is hypoxic, glycolysis is enhanced, and lactic acid production increases, which reduces the concentrations of reduced cytosolic coenzyme I (NADH) and reduced coenzyme II (NADPH), damages the body's antioxidant enzymes, the ability of the antioxidant system decreases. 6. The main hazards of free radicals are: a. Damage to biological membranes: the polyunsaturated fatty acids in the phospholipids of cell biological membranes are extremely prone to lipid peroxidation under the action of free radicals, which causes the mobility of the mitochondrial membrane to decrease, the permeability to increase, the mitochondria to expand, the release of lysosomal enzymes and enzyme inactivation and other damage; b. Damage to proteins and enzymes: Free radicals produced during lipid peroxidation can denature proteins; c. Damage to nucleic acids: Lipid peroxidation can lead to base modification and polynucleotide breaks, resulting in errors in the replication, transcription, and translation processes, as well as damage to the integrity and conformation of nucleic acids, leading to cell death. It can be seen that the changes in lipid peroxidation after exercise depend on the combined effects of oxygen radical production and antioxidant capacity.

The body's antioxidant system consists of antioxidant enzymes (such as superoxide dismutase SOD, catalase CAT, glutathione peroxidase GSH-Px, and peroxiredoxin PRX), antioxidant vitamins and their precursors (such as beta-carotene), glutathione (GSH), and other small molecule antioxidants (selenium, copper, manganese, etc.). The antioxidants that make up the antioxidant system are both endogenous and exogenous. Each antioxidant component has both a unique function in the cell and a complementary effect between the components. Disturbances in the homeostasis of the antioxidant system are associated with many physiological disturbances that occur during or after exercise, such as fatigue, muscle soreness, and impaired immune system function. The ability of the body's antioxidant system to scavenge free radicals can be increased by appropriately increasing exogenous antioxidants.

2 Mechanism and progress of black rice extract's antioxidant and free radical scavenging properties

2.1 Mechanism of black rice extract's antioxidant and free radical scavenging properties

Zhang Mingwei's research shows that anthocyanin compounds (a type of flavonoid) in black rice are the most important substance basis for its antioxidant effect. The main active ingredients responsible for the antioxidant effect were isolated and identified as malvin, pelargonidin-3,5-diglucoside, cyanidin-3-glucoside and cyanidin-3,5-diglucoside (see Figure 1). The total antioxidant capacity was measured and found to be in descending order: c>d>a>b.

Black rice Anthocyanin's 3-ring forms a conjugated system, which is a polyconjugated aromatic system with high biological activity.1 The mechanism of its antioxidant activity is related to the phenol-quinone balance and the formation of stable free radicals. On the one hand, due to the conjugation effect, the hydrogen atom on the phenolic hydroxyl group becomes more active and is easily removed to become a hydrogen donor, and a quinone reaction occurs to achieve phenol-quinone balance (see Figure 2) [12].

On the other hand, as a hydrogen donor, it can react with lipid compound radicals to form phenolic radicals. The unpaired electrons on the phenolic radical oxygen atoms are dispersed throughout the conjugated system, which is stable, thereby reducing the rate of transfer of the autoxidation chain reaction and inhibiting further oxidation of lipids. The mechanism of action is as follows:

AH+RO0·→ROOH+A · AH+RO·→ROH+A · The radicals RO · and RO0 · are electrophilic radicals, so electron-donating substituents on the aromatic ring increase the activity of the hydrogen atom on the phenolic hydroxyl group. Electron-withdrawing substituents, on the other hand, reduce the activity of the hydrogen atom on the phenolic carboxyl group. The strength of the antioxidant effect depends on two factors: the activity of the hydrogen atom on the phenolic carboxyl radical and the steric hindrance of the phenolic radical. A large steric hindrance slows down the rate of self-oxidation of the phenolic radical, which interrupts the chain reaction and improves the antioxidant effect. As can be seen from the above, the structural basis for the antioxidant activity of black rice pigment is the conjugated system formed by the three aromatic rings.

2.2 Research progress on the antioxidant and free radical scavenging properties of black rice extract

Jiang Ping and others studied the antioxidant activity of black rice anthocyanin, black bean anthocyanin, and purple cabbage anthocyanin, and found that black rice anthocyanin had the strongest antioxidant activity, which they believed was mainly related to cyanidin-3-glucoside [14]. It has also been reported that feeding rabbits and Apolipoprotein-E (Apo-E) gene-deficient mice a high-fat diet with 5% black rice bran added effectively removes active oxygen free radicals in these two experimental animals, inhibit the oxidation of low-density lipoprotein (LDL) 15-16J. Kaneda analyzed that Cy-3-G (cyanidin-3-glucoside) is the main antioxidant component in black rice bran]. The research group led by Tsuda has successively demonstrated that anthocyanin Cy-3-G can significantly reduce the production of lipid peroxides in rat serum, reduce free radical damage caused by rat liver ischemia-reperfusion, and protect vitamin C in the serum from oxidation [8-191]. In addition to its strong free radical scavenging ability, black rice anthocyanins have also been shown to significantly increase the activity of superoxide dismutase (SOD) and catalase (CAT) in the mouse liver, which may be another mechanism by which anthocyanins exert their antioxidant effect in the body [20].

It has also been reported that the enzymatic hydrolysate of black glutinous rice can significantly increase the activity of superoxide dismutase in the liver and glutathione peroxidase in whole blood, and reduce the content of lipid peroxides in the liver. This indicates that black rice extract can indirectly scavenge oxygen free radicals through the endogenous antioxidant enzyme system in vivo [21]. Lonsenjing] used chemiluminescence analysis to study the antioxidant activity of black rice pigments. The results showed that black rice extract has a greater inhibitory effect on whole blood chemiluminescence, that is, it has a greater scavenging effect on reactive oxygen species (OH, RO0) produced by the cellular system, and also has a certain scavenging effect on reactive oxygen species produced by the non-cellular system. Another study showed that the free radical scavenging effect of black rice extract was consistent with the results of in vivo experiments, which together proved that the active ingredients in black rice bran have strong antioxidant properties and can remove excess active oxygen free radicals in the body.

The large production of free radicals and the significant increase in plasma lipid peroxidation (LPO) are important causes of exercise fatigue123]. Therefore, moderate supplementation of black rice extract can eliminate free radicals produced by peroxidation, protect tissues such as muscles from damage, delay fatigue and promote recovery from fatigue.

3 Ideas for applying black rice extract to the development of sports drinks

Based on a review of relevant technical data, it is analysed that the effective application of black rice extract to the development of sports drinks requires four stages of work.

3.1 Data collection and experimental plan formulation

Collect theoretical and technical research data from home and abroad on the extraction of black rice anthocyanins, physical and chemical properties such as antioxidant properties and free radical scavenging, sports drink formulas, and experiments on the efficacy of sports drinks. Conduct an in-depth analysis and discussion of the current state of the development and application of black rice extracts in sports nutrition, focusing on the problems that exist and experimental methods that can be used as references. On this basis, formulate a plan for the development of black rice sports drinks.

3.2 Preparation of black rice extract

Black rice seed coat → black rice anthocyanin extraction → solid-liquid separation → supernatant → concentration → black rice anthocyanin concentrated paste.

3.3 Formula design for black rice extract sports drinks

Based on the reference sports drink formula and the functional research data of black rice anthocyanins, a preliminary formula design for the sports drink was proposed. On this basis, taste adaptability experiments were carried out; experiments to screen for the optimal amount of functional factors to be used; beverage stability experiments and preliminary efficacy evaluation experiments. The formula design for the black rice pigment sports drink was initially determined.

3.4 Evaluation of the efficacy of black rice extract sports drinks in humans

Volunteer participants were recruited to compare the changes in physiological and biochemical indicators such as blood lactate before and after the experiment through physical exercise and fatigue improvement experiments. Statistical analysis was used to establish and improve the evaluation method.

The key to the above four stages is the formulation design and efficacy evaluation of the black rice extract sports drink, and the technical difficulty lies in the stability of the drink, which is our follow-up work.

4 Conclusion

Black rice extract is a natural pigment resource with health-promoting properties. Anthocyanins in black rice extract have a conjugated system with three aromatic rings and have strong antioxidant activity and the ability to scavenge free radicals. The large production of free radicals and the significant increase in plasma lipid peroxidation (LPO) are important causes of exercise fatigue. A moderate amount of black rice extract can eliminate the free radicals produced by peroxidation, delay fatigue and promote recovery from fatigue. Existing data show that it is feasible to develop a health-promoting sports drink by applying black rice extract to a sports drink. This process requires four interrelated stages: formulation, black rice pigment extraction, formulation design experiments, and efficacy evaluation. Sports drinks are currently the darlings of the beverage industry, and the development of sports drinks with health benefits is promising.

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