Characterization, biological activities and safety evaluation of different varieties of Thai pigmented rice extracts for cosmetic applications

The study aimed to evaluate the total phenolic and flavonoid contents, biological activities and safety of different varieties of Thai pigmented rice for cosmetic applications. Five different varieties of Thai pigmented rice included Sang-Yod (SY), Mun-Poo (MP), Hom-Nin (HN), Rice Berry (RB), and Luem-Pua (LP). The rice grains were extracted using 50% ethanol and dried under vacuum. The total phenolic and flavonoid contents of rice extracts were in the range of 128-322 mg GAE/g extract and 86341 mg CE/g extract, respectively. LP extract showed the highest values for the total phenolic and flavonoid contents. Based on the antioxidant activities, LP showed the highest radical scavenging activities both DPPH and ABTS assays. Concerning the antityrosinase activity, all rice extracts exhibited a weak performance. In contrast, all rice extracts strongly inhibited the formation of advanced glycation end products (AGEs), the activity of collagenase and elastase enzyme. The obtained results from UV scanning showed the potential of rice extract as a UV absorber. The cytotoxicity using human fibroblast cell indicated the safe use of all rice extracts for topical administration. At the concentration of 400 μg/mL, the cell viability was higher than 50% for all rice extracts and LP showed the highest cell viability compared to others. As a result, rice extracts are a promising ingredient for cosmetics, especially for the anti-aging application. 141 V. Teeranachaideekul et al. and have been incorporated into cosmetic formulations is rice extract. Rice (Oryza sativa L., Poaceae) is one of the world’s leading food crops. Rice is a staple food for several countries including Thailand. Thailand has a long tradition of rice production and is one of the world’s largest rice exporters8. Thailand has a large number of rice varieties which differ in grain length, color, texture, thickness, aroma and growing condition. Rice and rice bran extracts have been reported to have biological activities which have potentials to be used in pharmaceutical9-12, nutraceutical13, 14 and cosmetic industries15-17. Especially in the cosmetic field, rice extract has been used as a skin and hair conditioning agent. The major composition of rice extract are proteins, carbohydrates, lipids, mineral ash and water. Recently, it has been found that rice extracts contain strong antioxidants which are phenolic acids , flavonoids, anthocyanins, proanthocyanins, tocopherols, γ-oryzanol and phytic acid16, 18. Although there are multiple published works related to rice extracts and its potential used in cosmetics, they have thus far only focused on identifying the compositions and the biological properties in each rice variety individually16, 18. However, to the best of our knowledge, the comparison across different types of rice, especially in the cosmetic field