Health Benefits of Black/Purple Rice
Purple rice, also identified as black rice or purple-black rice, refers to a range of different types of rice which belong to the species Oryza sativa L. Purple rice is ancient rice that originated from Hanzhong, Shanxi in China. Unpolished purple rice dons a hard surface with a white inner area, and contains purple black pigments (mainly due to anthocyanin) in the unpolished seed coat. Consumption of purple rice is common in Asia, and particularly Japan. In ancient times, purple rice was known for its ability to prolong youthfulness and life in general, and offer curative effects on anemia.
During the Chinese Ming period, purple rice was included in the Li Shi Zhen (a medical herb cuisine) due to its ability to promote vitality, pulmonary function and strengthen organs such as the spleen, liver, intestine, and stomach.
A number of studies have suggested that the consumption of purple rice could be associated with health effects. The health benefits are due to high amounts of fibre and contained phytochemicals which include tocotrienols, tocopherols, vitamin E complex, vitamin B complex, y-oryzanol, and phenolic compounds. Key secondary metabolites in purple rice include cyanidin-3-O-glucoside, anthocyanins, and peonidin-3-O-glucoside which are found in the pericarp and aleurone layers of the seeds (Pereira-Caro et al., 2013).
The purple pigment of purple rice is formed by anthocyanin which is known to possess antioxidant properties, scavenging for oxygen radicals generated in the body. This is critical for the prevention of carcinogenesis, aging, and general health promotion.
General functions and health benefits of purple rice extract
Animal studies suggest that the consumption of anthocyanins contained in black/purple rice by dyslypidemic rats on high fat diet will reduce platelet hyperglyceridemia, hyperactivity, maintaining optimum platelet function. A study conducted by Pereira-Caro et al. (2013) identified a variety of flavones and flavonols, carotenoids, anthocyanins, y-oryzanol in dehulled Japanese purple rice (Shen et al., 2009).
A number of studies have investigated functions and health benefits of purple rice, and some interesting facts have been established. According to analysis done by Oryza Oil & Fat Chemical Co., LTD, a Japanese food company, purple rice extract has the following functions and health benefits.
- Inhibition of carbohydrate absorption
The inhibition of carbohydrate absorption was evaluated using a-amylase (amylolytic enzyme) derived from swine pancreas and a-glucosidase ( disaccharidase) derived from rat intestine. The evaluation showed that purple rice extract has the ability to inhibit the activity of a-amylase and a-glucosidase.The inhibition of carbohydrate absorption is critical in the maintenance of a healthy body weight and metabolic function. High intake of carbohydrates is associated with an increased risk of major metabolic conditions such as cardiovascular disease, diabetes, arthritis, and gouts. The consumption of purple rice may therefore be associated with a reduced risk to these conditions (ORYZA OIL & FAT CHEMICAL CO., LTD.).
- Blood glucose control
Purple rice extract was able to inhibit the activity of carbohydrate degradation enzymes that result in an increase in blood glucose. The evaluation was conducted after glucose loading in normal rats. The inhibition was found to be more marked in sucrose, than starch, as assessed by glucose loading tests. This function confers an important health benefit, as abnormally high levels of glucose in the blood (pre-diabetic state) increases the risk of diabetes. Therefore, purple rice consumption may be beneficial in controlling blood glucose levels. A sucrose loading test conducted on 2 healthy males and 7 healthy females showed that purple rice extract has the ability to significantly inhibit glucose loading. This confers a health benefit by ensuring that blood glucose levels do not rise above acceptable limits (ORYZA OIL & FAT CHEMICAL CO., LTD.).
- Antioxidant activity
Reactive oxygen species (superoxide, hydroxy radical) are generated in the body resulting cell damage, which could in turn trigger carcinogenesis, inflammation, in addition to contributing to the aging process and certain mental disorders. Reactive oxygen species cause wrinkles, spots, and freckles on the skin. Purple rice exhibits SOD-like activity and DPPH radical scavenging activity which are very important in the prevention of lifestyle-related disorders that result from active oxygen (Ichikawa et al., 2001).
Purple rice extract has also exhibited the ability to increase reduced vitamin C levels. Reduced vitamin C (L-ascorbic acid) has strong antioxidant activity but it is usually oxidized into oxidized vitamin C without antioxidant activity. The action of purple rice extract could therefore result in the stabilization of reduced vitamin C and, therefore, enhance its contribution to antioxidant activity (ORYZA OIL & FAT CHEMICAL CO., LTD.).
Purple rice promotes healthy skin through various actions on enzymes involved in different skin processes.
the primary phytochemical components in Purple Rice, and their Known Health Benefits:
- Promotion of healthy skin through elastase inhibition
Elastin is a key protein for elastic tissues such as the skin. The protein is found in high amounts in the skin and its degradation has been associated with reduced skin elasticity and the formation of sags and wrinkles. An analysis conducted by Oryza Oil & Fat Chemical Co., LTD showed that purple rice extract has the ability to inhibit elastase (an enzyme involved in elastin degradation) and thereby ensuring healthy skin through maintenance of healthy amounts of elastin. A number of commercial skin products incorporate purple rice to help achieve a healthier and younger looking skin .
- Promotion of healthy Skin through collagenase inhibition
Collagen, an extracellular structural protein, accounts for about 90% of the skin dermis, where it is found distributed in all layers. In addition to maintaining skin strength, collagen is also needed for elasticity. Collagenase enzyme degrades collagen in the skin, resulting in the formation of sags and wrinkles, a common aging phenomenon of the skin. Purple rice extract has shown the capacity to inhibit collagen degradation by collagenase. This is useful in the maintenance of adequate amounts of collagen in the skin and, hence reducing the rate at which wrinkles and sags are formed (Shen et al., 2009).
- Promotion of healthy skin through hyaluronidase inhibition
Hyaluronic acid plays a crucial role in cell formation and protection, water retention in tissues, formation and integrity of the skin tissue, and maintenance of flexibility in the skin. Reduction in the level of hyaluronic acid reduces moisture content and tension of the skin tissue, resulting in the formation of sagging skin and age spots. Hyaluronic acid formed in the body is quickly degraded by hyaluronidase. Purple rice extract has shown the ability to prevent the degradation of hyaluronic acid by inhibiting the action of hyaluronidase. This helps maintain adequate amounts of hyaluronic acid needed for healthy skin tissue.
Many of the phytochemicals contained in purple rice have been clinically associated with health benefits.
Anthocyanins are mainly located in the pericap of the purple rice. Main anthocyanins detected in purple rice include cyanidin-3-O-glucoside (89.0% of total anthocyanins) and peonidin-3-O-glucoside (9.3%) in addition to fiveminor components (<2%) which were derivatives of cyanidin,peonidin, and pelargonidin. Studies indicate that Anthocyanins may possess ant-inflammatory and anti-carcinogenic activity, obesity control, and cardiovascular disease control and diabetes alleviation properties (He & Giusti, 2010).
- Flavone and flavonol glycosides
Small quantities of flavones and flavonol glycosides have also been detected in purple rice. Flavone and flavonol compounds that are mainly detected include apigenin-6/8-C-pentoside-8/6-C-hexoside (44% of total), quercetin-3-O-glucoside (29%), quercetin-3-O-rutinoside (16%), luteolin-6/8-C-arabinosyl-6/8-C-glucoside (8%), and isorhamnetin-3-O-glucoside (3%) (Pereira-Caro et al., 2013). These compounds are known to possess antioxidant, anti-inflammatory, ant-cancer, and antibacterial properties, and may also be helpful in the prevention of cardiovascular disease (Ichikawa et al., 2001).
Key carotenoids found in the Japanese purple rice include xanthophylls, lutein, and zeaxanthin. Carotenoids may be helpful in reducing the risk of a number of diseases, and particularly eye disease and certain cancers.
- Y- Oryzanol
Purple rice contains significant amounts of y-oryzanol. This compound has been found to exhibit strong antioxidant properties both in vivo and in vitro. Generally, the phytochemicals contained purple rice possesses significant health benefits, including the ability to suppress carcinogenesis in several human cancer models, and the ability to reduce oxidative stress by enhancing the potent free-radical scavenger, superoxide dismutase.
He, J., & Giusti, M. M. (2010). Anthocyanins: natural colorants with health-promoting properties. Annu Rev Food Sci Technol. , 1:163-87.
Ichikawa, H., Ichiyanagi, T., Xu, B., Yoshii, Y., Nakajima, M., & Konishi, T. (2001). Antioxidant activity of anthocyanin extract from purple black rice.Journal of Medicinal Food, 4(4), 211-218.
ORYZA OIL & FAT CHEMICAL CO., LTD. (n.d.). Purple Rice Extract. Retrieved September 4, 2015, from http://www.oryza.co.jp/: http://www.oryza.co.jp/html/english/pdf/kuro-e.pdf
Pereira-Caro, G., Watanabe, S., Crozier, A., Fujimura, T., Yokota, T., & Ashihara, H. (2013). Phytochemical profile of a Japanese black–purple rice.Food chemistry, 141(3), 2821-2827.
Shen, Y., Jin, L., Xiao, P., Lu, Y., & Bao, J. (2009). Total phenolics, flavonoids, antioxidant capacity in rice grain and their relations to grain color, size and weight. Journal of Cereal Science, 49(1), 106-111.
FDA Disclaimer: This product is a nutritional supplement and as such is not meant to treat, prevent, mitigate or cure any disease.