Investigation of Bioactive Compounds, Free Radical Scavenging Activities, Cytotoxicity, and Anti-Inflammatory Properties of Thai RD43 Rice Extracts for Use as Novel Cosmetic Ingredients

This study investigated the bioactive compounds, antioxidant, anti-inflammatory, and cytotoxic activities of ethanolic extracts from white and brown RD43 rice, and evaluated the stability of a topical emulsion formulation containing the selected extract. Extraction with 70% ethanol by maceration yielded a higher extract percentage from brown rice than from white rice. Both extracts contained phenolic acids, flavonoids, and γ-oryzanol; however, the brown rice extract exhibited significantly higher levels of total phenolics, flavonoids, γ-oryzanol, and phenolic acids. Consequently, the brown rice extract showed superior antioxidant activity, with DPPH radical scavenging activity (IC₅₀=1.90±0.05 mg/mL), ferric reducing antioxidant power (374.12±2.75 mg TE/g of extract), hydroxyl radical scavenging activity (223.77±3.27 mg TE/g of extract), and superoxide radical scavenging activity (176.42±6.01 mg TE/g of extract). Cytotoxicity evaluation demonstrated that both extracts were non-toxic to normal human dermal fibroblast (NHDF) cells. Furthermore, the brown rice extract significantly inhibited nitric oxide production in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages (p<0.05), indicating anti-inflammatory activity. Due to its superior biological activities, the brown rice extract was incorporated into a cream formulation, which exhibited acceptable physicochemical characteristics and preliminary stability during storage. These findings suggest that RD43 brown rice extract is a promising natural source of bioactive compounds with antioxidant and anti-inflammatory properties and has potential for application as a functional ingredient in cosmetic formulations aimed at protecting the skin against oxidative stress and inflammation.