Abstract: The aims of the study were to measure and compare the content of the bioactive compounds in natural rice bran oils (NRBOs) and investigate for anti-inflammatory activity through inhibition effect on nitric oxide (NO) and inducible nitric oxide synthase (iNOS) in RAW264.7 mouse macrophage cells. NRBOs were prepared from colored and non-pigmented rice in northern Thailand using the cold-press technique. The bioactive compound constituents in NRBOs, including tocotrienols, tocopherols, and γ-oryzanol were analyzed by reversed-phase HPLC. Then, anti-inflammatory activity was investigated through an inhibition effect on NO and iNOS production induced by combined lipopolysaccharide (LPS)-interferon-g (IFN-g) in RAW264.7 mouse macrophage cells. The results demonstrated that NRBOs prepared from purple rice, red rice and non-pigmented rice consist of δ, γ, and α-tocotrienol, δ, β, γ, and α-tocopherol, and γ-oryzanol. γ-Oryzanol, γ-tocotrienol, and γ-tocopherol were the major bioactive compounds in NRBOs. NRBOs prepared from purple rice bran exhibited higher concentrations of the bioactive compounds than red rice bran and non-pigmented rice bran, respectively. Khao¢ Gam Leum-Phua (KGLP) exhibited the highest amount of δ, γ and α-tocotrienol, δ, γ, β and α-tocopherol, and γ-oryzanol. Interestingly, all NRBOs inhibited NO and iNOS production by LPS/IFN-γ-stimulated RAW264.7 cells. Additionally, NRBO prepared from KGLP exhibited the highest inhibitory activity on NO and iNOS production. There may a potential use for pigmented NRBOs especially cultivated in mountainous areas which containing high amounts of tocotrienols, tocopherols, and γ-oryzanol, as a natural anti-inflammatory active ingredient in nutraceutical and cosmeceutical products.
Keywords: Natural rice bran oil, Tocotrienols, Tocopherols, γ-Oryzanol, Anti-inflammatory.