Comparative Evaluation of Potential Phytochemicals in Brain, Husk and Endosperm of Red Rice Found in Kerala

Abstract

Rice is the dominant cereal crop in most Asian countries and staple food for more than half of the world’s population. Rice plays a key role in the energy needs of people in the developing countries due to non- affordability of other sources. In India rice is considered a part of the tradition. Thus whole rice being a rich source of carbohydrates, antioxidants such as poly phenolics, - oryzanol, E-vitamines can be utilized as an excellent functional food component. Daily intake can contribute 328-361 kcal and along with it the prevention of chronic diseases such as heart disease, obesity, Type II diabetes and cancers. Thus studies on coloured rice varieties are important as they have higher content of phytonutrients compared to the colourless varieties. The present study concentrates on the phytochemical distribution in the bran, husk and short and long grain endosperm of the traditional red rice variety found in Kerala, which is commonly known as ‘matta‘ rice. The microscopical characters were observed and the major features such as aleurone grains and oil globules present in the bran layer, the lignified cells, the cuticle and schlerenchymatous cells in the husk and rice starch were observed. The physicochemical analysis was done to study the bulkiness and flow property of the rice bran and rice husk. The successive solvent extraction of the four portions were carried out using hexane toluene pet ether chloroform ethyl acetate acetone methanol ethanol water done and the bound phenolics from the rice flour (long grain and short grain) was done. These extracts were subjected to various phytochemical tests and thin layer chromatographic evaluation. Comparing the results it was able to study the distribution of major secondary and primary metabolites present in the different portions of red rice. Also five potential extracts were selected and the phytoconstituents present in them were catogorized. These five extracts were subjected to HPTLC profiling along with comparison with four reference standards such as rutin, tocopherol, gallic acid and sterol were done. Rf values for some compounds were found. Tocopherol which is found normally in higher level in normal rice bran was not detected in the red rice bran. This may be due to the leeching of vitamins during the storage of the rice bran or may be due to its action against the degradation that might have occured in the test sample.The methanol extracts, especially that of the husk showed a higher concentration of phenolics and flavonoids. Thus their total phenolic content and total flavonoid content were assessed in bran, husk and endosperm. Two antioxidant methods such as DPPH radical scavenging activity and the ABTS radical scavenging method were done for the methanolic extracts. Husk showed a significant phenolic content. The water extracts prepared by two methods, i.e., successive solvent extraction and by using simulated gastrointestinal pH both were assessed for total phenolic content and DPPH radical scavenging activity. Bound phenolics extract did not give significant activity and also the short grain water extract. The antimicrobial assay was carried out for the methanolic extract of red rice husk. In the anti bacterial assay an increase in the activity was observed with the increase in the concentration. The antifungal activity was absent in the methanolic extract of red rice husk. Newertechnologies could be used to isolate phytonutrients and prepare a wide range of value added products. The increasing interest in natural antioxidants in the food and medicinal industries owing to the toxicity related with the usage of synthetic antioxidants can be exploited to increase the utilization of various benefits of ‘matta’ rice by products in industries.