Antioxidant properties of milled rice extract and rice bran oil from Dok Pradu red glutinous rice: cellular ROS attenuation by the milled rice extract in UVB-induced HaCaT cells

Dok Pradu red glutinous rice ( Oryza sativa L.) is a promising source of bioactive compounds. This study investigated the phytochemical composition and antioxidant functionality of two fractions derived from the same post-milling rice material: the milled rice extract and rice bran oil. The extract was enriched in phenolic compounds and anthocyanins, whereas the oil contained higher levels of lipophilic antioxidants, particularly γ-oryzanol and tocopherols. Accordingly, the extract exhibited greater total phenolic and flavonoid contents, ferric reducing antioxidant power, and radical-scavenging activity than the oil fraction. In UVB-induced HaCaT keratinocytes, the extract maintained cell viability above 80% and attenuated intracellular reactive oxygen species at 75 μg/mL. However, its effects on viability recovery, superoxide dismutase activity, and UVB-responsive gene expression were limited. These findings suggest that the milled rice extract exerts selective intracellular antioxidant activity under UVB stress, reducing ROS levels while showing limited modulation of downstream cellular responses.