Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68 Page 69 Page 70 Page 71 Page 72 Page 73 Page 74 Page 75 Page 7671 IREC Farmers' Newsletter No. 195 ­ – Rice R&D 2016 grow to $305 billion by the year 2020. The unique composition of rice bran protein, coupled with its low allergenicity compared with many other cereal and legume proteins, represents a unique opportunity for the rice industry. Rice bran protein could be developed into high-valued bioactive ingredients for functional food and nutraceutical supplements to replace some of the standard prescription drugs for managing a range of diseases and health conditions. About the project This RIRDC-funded project, with in-kind support from SunRice, was initiated with the aim of developing rice bran protein- based bioactive ingredients that can be used in functional food, nutraceutical and pharmaceutical products. The project was conducted in three phases. In the first phase, four different types of proteins, namely albumin, globulin, prolamin and glutelin, were sequentially extracted from rice bran using a modified Osborne procedure developed in the project. The extracted proteins were hydrolysed (broken down to component molecules with water) using four commercial protease preparations, Alcalase, Neutrase, Flavourzyme and Protamex. These enzymes were selected for their hydrolytic efficiency and safety because they have been widely used in the food industry. The hydrolysates (the products resulting from hydrolysing the proteins) were analysed for their antioxidant, antidiabetic and antihypertensive activities. In the second phase, the rice bran protein hydrolysates were separated into three fractions based on the molecular weight of the peptides: small, medium and large. The bioactivities of each fraction were measured. The fractions with the highest activities were purified and isolated and the bioactivities of the isolated fractions were also measured. Finally, the isolated fractions with the highest bioactivities were analysed to determine the peptide sequences present in them. The peptides found were then searched against the bioactivity database BIOPEP to identify peptide sequences that have been reported to have antioxidant, antidiabetic and antihypertensive activities. In the third and final phase, the rice bran proteins went through an artificial digestion procedure that mimics the human digestion process. The proteins were first subjected to amylase digestion for five minutes, followed by pepsin digestion for two hours and pancreatic digestion for another hour under carefully controlled conditions that mimic digestion during chewing (and passage to the stomach), in the stomach and the small intestine. The protein hydrolysates (digests) were also subjected to fractionation and isolation and characterised for their bioactivities as described previously. Key findings The analysis found that the hydrolysates of rice bran proteins possess significant in vitro antioxidant activities as well as capacity to block the activities of physiologically important enzymes. These enzymes are closely linked with conditions such as diabetes and hypertension (high blood pressure). Two enzymes found in digestive fluid, α-amylase and α-glucosidase, are responsible for the digestion of starch, with resultant release of glucose. The released glucose is rapidly absorbed by the body, leading to a sugar rush in the blood after a starchy meal, which can be dangerous for diabetic patients. Blockage of these two enzymes is a key strategy in diabetic care. In this project, the α-amylase and α-glucosidase inhibition capacities of albumin and glutelin hydrolysates produced by Protamex and Alcalase were found to be particularly strong (Figure 1), comparable in magnitude to those of the standard antidiabetic drug, acarbose. When the amount of the former that can be safely consumed is taken into consideration, this demonstrates that these hydrolysates have the potential to be developed into an alternative to diabetes management drugs such as acarbose in the form of dietary or nutraceutical supplements. Angiotensin converting enzyme, or ACE, is an enzyme involved in the regulation of blood pressure. Put simply, persistently high ACE activity in the blood will lead to high blood pressure, and several blood pressure-lowering drugs, such as captopril, work because of their capacity to block ACE. The ACE-inhibition effects of rice bran protein hydrolysates are not as potent as that of captopril, but they are still quite significant (Figure 2), because we can consume thousands of times more of rice bran protein without any side effects as is the case with drugs such as captopril. Antioxidants play a crucial role in health because they mitigate oxidative stress in our body. Oxidative stress can cause damage to body tissues and interfere with physiological functions and processes leading to various diseases. A slow, steady accumulation of oxidative “debris” in the body contributes to the development of a number of chronic diseases including inflammation, autoimmune disorders, diabetes, cardiovascular diseases and cancer. Antioxidants can mitigate such oxidative stress by acting as scavengers that rid the body of the toxic chemicals. Phenolic compounds in fruits and vegetables are well known antioxidants. We assessed the antioxidant activities of rice bran hydrolysates using several methods, and found the activities are very strong (Figure 3). This shows that these protein hydrolysates can provide health benefits in similar ways as phenolic compounds do. When rice bran proteins were subjected to an in vitro simulated human digestion, the resultant digests (hydrolysates) are also found to exhibit significant antioxidant, α-glucosidase and ACE-inhibitory activities. This means that consumption of rice bran proteins can potentially lead to generation of bioactive peptides in the digestive tract with substantial health benefits. The α-glucosidase inhibitory activities of the simulated human digests of rice bran proteins, and albumin and glutelin in particular, are especially strong, comparable to that of the standard diabetic drug acarbose. This suggests that rice bran protein supplements or a diet rich in these proteins could potentially have a significant role in managing this prevalent disorder. The bioactivities of peptides derived from rice bran proteins are strongly influenced by their molecular sizes. Peptides with smaller molecular weight have much greater activities than the larger peptides. The net charge of peptides also affects the biological activities of the hydrolysates and peptides, but the effects are not as prominent as that of molecular size. Analysis identified a large number of peptide sequences in the most active peptide fractions and subsequent search of the peptide sequences against the BIOPEP database revealed that most of them contained sequences with antioxidant, α-glucosidase or ACE-inhibition activities. Several of the bioactive sequences appeared multiple times in different peptides in the hydrolysate fractions. Implications for the rice industry The findings of the project have several significant implications for the rice industry, the general public, scientific community and relevant policy makers. For the rice industry, the findings signify a significant opportunity for developing rice bran-based functional food and nutraceutical products. Such products can potentially replace or supplement