Antioxidant, Anti-Inflammatory, and Bone-Remodeling Modulatory Activities of Thai Pigmented and Non-Pigmented Rice Bran Oils Containing Tocols and γ-Oryzanol

Rice bran oil (RBO) is a rich source of lipophilic bioactive compounds that may contribute to antioxidant, anti-inflammatory, and bone-health-promoting activities. This study investigated the effects of RBOs containing tocopherols, tocotrienols, and γ-oryzanol derived from Thai pigmented and non-pigmented rice cultivars on oxidative stress, inflammatory responses, and bone-remodeling-related activities. The content of tocopherols, tocotrienols, and γ-oryzanol was determined by high-performance liquid chromatography (HPLC). Reactive oxygen species (ROS) production was determined in human fetal osteoblast (hFOB 1.19) cells where nitric oxide (NO) and inducible nitric oxide synthase (iNOS) production were evaluated in RAW264.7 cells. Following compositional profiling and correlation analyses of antioxidant and anti-inflammatory activities, three representative RBOs were subsequently evaluated for their effects on bone-remodeling-related activities in hFOB 1.19 cells through alkaline phosphatase (ALP) activity and the production of osteocalcin (OC), osteoprotegerin (OPG), and receptor activator of nuclear factor kappa-B ligand (RANKL). Additionally, calcification was investigated by Alizarin Red S staining. Pigmented RBOs, particularly Khao’ Hom Nil and RD69, contained higher levels of tocopherols, tocotrienols, and γ-oryzanol than non-pigmented RBOs. These oils significantly suppressed ROS, NO, and iNOS production, which correlated with tocopherol, tocotrienol, and γ-oryzanol content, while enhancing ALP activity, OC and OPG production, reducing RANKL levels and the RANKL/OPG ratio, and promoting matrix mineralization. Overall, pigmented RBOs represent promising natural sources of lipophilic bioactive compounds with potential antioxidant, anti-inflammatory, and bone-remodeling-related activities under in vitro conditions.