What Is the Health Benefit of Black Rice Anthocyanin?

Rice is one of the world's three major food crops. More than half of the world's population uses rice as their staple food, and it is one of the most important crops cultivated in China. Rice is classified according to the color of the grains. In addition to the common white rice, there are also black rice, purple rice, red rice, green rice and yellow rice. The reason for the different colors of these colored rice grains is mainly that colored rice is rich in anthocyanin.

During the development of rice, anthocyanin is deposited in the pericarp, seed coat and aleurone layer, and the accumulation of pigments causes the brown rice to appear in various colors. Studies have shown that the darker the grain color, the more anthocyanin it contains, and the stronger its antioxidant and anti-aging properties [1]. Black rice has the darkest grain color of all colored rice, so the effect of black rice pigment is also the strongest among all colored rice. Black rice is very nutritious and has a wide range of applications in terms of both food and medicine. Since ancient times, black rice has enjoyed a reputation as the “king of all rice in the world”, “black pearl”, “sacred rice”, “medicine rice” and “longevity rice”, In Chinese folk culture, it is said that “black is always a remedy”. Anthocyanin is a type of flavonoid compound. As an important active substance in rice, it not only gives the rice its excellent colour, but also has physiological functions such as anti-oxidation, lowering blood lipids, inhibiting cancer and anti-cancer, and inhibiting bacteria, anti-inflammatory and anti-allergy.

1 Antioxidant

The most important active function of anthocyanin is its antioxidant capacity. Black rice anthocyanin can be used as a photoprotectant to eliminate free radicals produced during photosynthesis [2], enhance the antioxidant capacity of serum and liver, and significantly enhance the biological activity of glutathione peroxidase and superoxide dismutase [3]. Using the water-soluble antioxidant tocopherol as a control, the antioxidant activity of the anthocyanin extract from purple black rice is 10 to 25 times that of the same concentration of tocopherol [4]. The mechanism of anthocyanin antioxidant has been studied relatively thoroughly, mainly in the following ways: ①Anthocyanin contains multiple phenolic hydroxyl groups in its structure, which can inhibit or directly scavenge free radicals and prevent oxidative damage. 2. Anthocyanin can remove free radicals by activating the antioxidant enzyme system (including glutathione peroxidase, catalase and superoxide dismutase, etc.). In addition, anthocyanin can also chelate metal ions, cooperate with antioxidants to reduce or remove free radical damage to the body.

2 Lowering blood lipids

Anthocyanin in black rice can effectively protect the kidney lipid peroxidation reaction in experimental mice [5], and can significantly inhibit the oxidative modification of human low-density lipoprotein. Yu Xiaoping et al. studied the effect of an anthocyanin extract from black rice husk on unstable plaques caused by atherosclerosis and found that the anthocyanin extract can significantly reduce the levels of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, cholesterol and triglyceride levels in the blood, and reduces the frequency of unstable plaque formation. Its effect is similar to that of the clinically used lipid-lowering drug simvastatin, significantly improving lipid metabolism and effectively reducing blood lipid levels [6].

3 Inhibits tumor cell growth

Black rice anthocyanins can significantly inhibit tumor cell proliferation and effectively induce apoptosis of tumor cells. The epidermal growth factor receptor (HER-2/neu) is a membrane receptor protein encoded by the proto-oncogene (ErbB-2). It is highly expressed in many types of malignant tumors, such as common colon cancer, ovarian cancer and breast cancer. Studies have shown that black rice anthocyanins can significantly inhibit the phosphorylation of HER-2/neu and extracellular regulated protein kinases (ERK-1/-2), and blocks the translocation of the transcription factor protein family member NF-κB p65 to the nucleus, thereby inhibiting the expression of genes such as vascular endothelial growth factor, matrix metalloproteinase, and urokinase plasminogen activator at the mRNA level, and blocking the HER-2/neu and downstream signal pathways (EGFR/Ras/MAPK), thereby inhibiting the expression of pro-angiogenic factors in tumor cells [7]. In addition, black rice anthocyanins can significantly inhibit the growth of HL-60 leukemia cells [8], the lung metastasis of breast cancer cell xenografts [9] and the proliferation of liver cancer cells [10]. They can also significantly inhibit the gene mutation of mammalian cells caused by tetranitroquinoline-1-oxide and inhibit the generation of tumor cells induced by phorbol [11].

4 Antibacterial, anti-inflammatory and anti-allergic effects

Anthocyanin can increase the permeability of cell membranes, inhibit cell division, and cause abnormal cell growth or cell death, thereby exhibiting antibacterial activity [12]. It can effectively inhibit the growth of Staphylococcus aureus and Escherichia coli [13]. Studies have shown that the transcription and translation of inducible nitric oxide synthase (iNOS) and inflammatory factor cyclooxygenase (COX-2) require the regulation of the nuclear transcription factor (NF-κB). Anthocyanin from black rice husk can significantly inhibit the physiological function of the nuclear transcription factor (NF-κB) and effectively reduce the plaques formed by atherosclerosis, thereby inhibiting inflammation [14]. Black rice anthocyanins can regulate the imbalance between interferon-γ and interleukin-4, thereby effectively reducing the infiltration of inflammatory cells into body tissues [15].

Anthocyanin in black rice significantly increases tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) by inhibiting the activation of aminopeptide endopeptidase in rat adipose tissue, thereby accelerating translocation of glucose transport. The overall content of oxidized glutathione and malondialdehyde, a lipid peroxide product, in the blood of rats fed anthocyanin was significantly lower, Anthocyanin supplementation in the diet can effectively improve the sensitivity of experimental mice to insulin, indicating an insulin-sensitizing effect of anthocyanins [16]. Anthocyanin extract can significantly inhibit the release of foot amine and the internal calcium uptake of cells, and significantly reduce the expression of interleukin 6 and tumor necrosis factor α protein, thereby significantly inhibiting the allergic reaction of experimental rats [17].

5 Other effects

Black rice Anthocyanin can effectively prevent cardiovascular disease, chronic disorders, degenerative diseases [18] and atherosclerosis [19]. It also has a significant protective effect on peroxidation damage to vascular endothelial cells caused by oxidized low-density lipoproteins [20], photochemical damage to the retina [21], and CCl4-induced subacute liver injury [22]. In addition, the alcoholic extract of black rice husk (anthocyanin) can inhibit tyrosinase activity, thereby inhibiting the synthesis of melanin and reducing skin pigmentation. Black rice anthocyanin can reduce skin pigmentation [23], lower the glycemic index, and prevent obesity and diabetes [24].

6 Conclusion

In recent years, with environmental degradation and changes in people's lifestyles, the incidence of modern chronic diseases such as hyperlipidemia, hyperglycemia, coronary heart disease and cancer has continued to rise. Currently, about 45% of the population in China is in a sub-healthy state. Two-thirds of the population in China uses rice as their staple food, and the research and development of functional rice will be of great practical significance. Anthocyanin is a flavonoid compound.  an important active substance in rice, not only gives it an excellent color, but also has physiological activities such as anti-oxidation, lowering blood lipids, antibacterial, anti-inflammatory and anti-cancer. Effective intake of Anthocyanin through eating black rice in the daily diet has become an effective means for people to achieve “food supplement” and “diet therapy”, and is playing an increasingly important role in the field of functional food development and research.

References:

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