Evaluation of Antioxidant and Anti-Aging Activities of Thai Rice Germ Extracts

Aging in humans is a natural process characterized by the accumulation of oxygen-derived free radicals, leading to cellular and tissue damage and aging-related diseases. Bioactive compounds from plants, known for their antioxidant properties, can mitigate the effects of aging by scavenging these free radicals. The present study aimed to explore the antioxidant and anti-aging properties of commercial rice germ extracts. Fifteen types of extensively commercial rice germ (RG) products from Thailand were coded as RG1 - RG15. These products were assessed for phenolic content and antioxidant activity. The rice germ with the highest phenolic content and antioxidant activity was further investigated for anti-aging properties and endogenous antioxidant activities (SOD, CAT and GPx). Additionally, protein expressions related to longevity were analyzed using western blot analysis. Among the 15 RG products, RG1 exhibited the highest total phenolic content (21.07 ± 0.54 mg GAE/g dry weight) and significant antioxidant activities in ORAC, FRAP and DPPH scavenging assays, showing approximately 748.22 ± 20.30 µmol Trolox/g dry weight, 3.82 ± 0.10 mg GAE/g dry weight and 75.10 ± 0.19 % inhibition of free radicals, respectively, compared to RG2 - RG15. Consequently, RG1 was selected for further anti-aging and in vitro studies. The anti-aging assays demonstrated that rice germ extract significantly inhibited collagenase, elastase and hyaluronidase in a dose-dependent manner (62.5 - 500 µg/mL). The extract also enhanced endogenous antioxidant activities (SOD, CAT and GPx) in H2O2-treated cells in a dose-dependent manner. Moreover, RG1 extract induced the expression of longevity-related proteins such as AMPK, FoxO and SIRT, while reducing the expression of mTOR and Akt proteins. Rice germ extract has high phenolic content and provides antioxidant and antiaging activities. In addition, rice germ can inhibit aging-related enzymes via inducing endogenous antioxidants and the longevity-related protein expression. HIGHLIGHTS Rice germ extract exhibits exceptionally high phenolic content and powerful antioxidant activity, making it a potent agent against oxidative stress. Rice germ extract demonstrates anti-aging potential by enhancing endogenous antioxidant systems, promoting cellular protection and longevity. Rice germ extract regulates key longevity-related pathways by inducing AMPK, FoxO and SIRT proteins while suppressing the expression of mTOR and Akt, which are associated with aging and cellular stress. GRAPHICAL ABSTRACT