**3.1 Antioxidant activities**

*Phytochemicals in Human Health*

other health benefits [53, 54].

white rice [57].

flavanol content [50].

fatty acids but also occurs as a result of the high contents of γ-oryzanol, tocopherols, and tocotrienols that reveal strong oxidative stability along with a range of

The protein content present in rice bran of brown rice is characterized as a good source of protein that is nutritionally superior and hypoallergenic in nature. Rice bran is a rich source of essential amino acids such as lysine, which seems to be present in minute quantities in other cereal grains [55, 56]. The proteins in rice bran are highly digestible and can be utilized as an effective food ingredient. Rice bran is rich in dietary fiber, and, consequently, the rice bran by-products of rice processing are now often present in food commodities and functional foods that have been marketed for the ability to add dietary fiber to the diets of consumers and to offer health benefits in terms of daily nutrition. Additionally, brown rice possesses high contents of a variety of nutrients, such as fiber, vitamins, and minerals that are lost during the process of refining and milling in the production of white rice within the rice agro-industry. Notably, brown rice possesses four times as much dietary fiber as

White rice is a major source of energy nourishment for the world's population, especially in Asian countries. However, the carbohydrate content in white rice accounts for 80% of its makeup, which is considered a higher amount than wheat. Wheat is a popular grain among European countries and contains a lessor proportion of carbohydrates (approximately 50–70%) [58]. For this reason, there are concerns that white rice possesses a high glycemic content and that it may not be a suitable source of carbohydrates for people who have weight problems. It is interesting to note that white rice does not contain anthocyanins and proanthocyanidins, which are the important phytochemicals that are found in black rice and red rice, respectively, particularly in portions of rice germ and bran extracts. While total flavonols and phenolic compounds are observed to be significantly high in pigmented rice, nonpigmented rice such as white rice possesses a minute quantity of flavone/

**3. Pigmented rice and bioactivities that benefit health**

Phytochemicals found in pigmented rice (brown, black, purple, and red rice) are not present in white rice because many valuable phytochemicals, fiber, vitamins, and nutrients are lost during the processes of refining and milling [57]. Since brown rice contains higher dietary fiber and nutrients, previous studies have revealed that when compared to a white rice diet, a brown rice diet was found to significantly reduce weight, body mass index (BMI), and the circumference of the waist and hips, as well as to lower diastole blood pressure and inflammatory biomarkers such as C-reactive proteins (CRP). Arabinoxylan and β-glucan, prebiotics that are found in brown rice, are beneficial for human gut microbiota such as *Bifidobacterium* and *Lactobacillus*. They are considered as contributing factors in producing an anti-obesity effect [57, 59]. Moreover, in terms of their antidiabetic effects, brown rice was used as an intervention for preventing type 2 diabetes. This is likely because one of their components, ϒ-oryzanol, plays an important role in controlling high-fat diet-induced ER stress in the hypothalamus, which helps in reducing the preference for fatty foods [60]. ϒ-Oryzanol in brown rice has also been found to prevent the apoptosis of pancreatic β cells and to reduce levels of blood cholesterol [61]. Dietary rice brans that give brown rice its brown color also reveal potent anticancer activities through their antioxidant activity, as well as offering antiproliferation, immune modulation, and mucosal

**10**

protection [62, 63].

The antioxidant activities of black and red rice and their crude extracts have been studied, and the results demonstrated that the addition of the pigmented rice could increase antioxidant capacity, both in vivo and in vitro [64–66]. In a study involving the supplementation of diets with black rice pigment fractions, the diets that attenuated atherosclerotic plaque formation in apolipoprotein E-deficient mice [66] and the anthocyanin-rich extract of the black rice might play an important role in the enhancement of atherosclerotic plaque stabilization [8]. In another study, a mixture of brown and black rice improved the lipid profiles and antioxidant status in rats [67]. Another animal study also demonstrated that black rice bran pigment effectively escalated hepatic antioxidant enzyme activities including superoxide dismutase and glutathione peroxidase in high-cholesterol-fed rats [68]. In addition to the in vivo studies, in a cell culture experiment, superoxide anions and reactive oxygen species were significantly suppressed after black rice extract exposure in HepG2 hepatocellular carcinoma [17]. When the antioxidant activities of pigmented rice were compared with those of nonpigmented rice in several studies [30, 41], the results demonstrated that the extracts from pigmented rice displayed higher antioxidant activity than did the nonpigmented rice. In another study, the radical scavenging activities of the extracts from white, black, and red rice were tested. The highest activity was observed in red rice (2.77 μmol of Trolox or vitamin E equivalents/ml), followed by black (0.92 μmol) and white (0.26 μmol) [41, 42]. Polymeric proanthocyanidins play an important role as radical-scavenging components in red rice. The relationships between the antioxidant activities and the components of pigmented rice were explored [41, 69, 70]. The antioxidant activities correlated well with the content of polyphenols and phytochemicals that contribute to the intense color of the pigmented rice. Interestingly, some studies have shown that the antioxidant activity of black rice may be reduced by up to 53% during cooking [71–73].
