Spice fixed oils as a new source of γ-oryzanol: nutraceutical characterization of fixed oils from selected spices

γ-Oryzanol is an important group of nutraceuticals that play a key role in addressing metabolic disorders. This study, for the first time, examined volatile-free spice fixed oils (FOs) as an alternate plant source for γ-oryzanol and other nutraceuticals (phenolics, flavonoids, phytosterols, and tocopherols) using HPLC, HR-MS and NMR. The in vitro antioxidant activities of FOs were also analysed. The selected spices were Alpinia galanga, Cinnamomum zeylanicum, Trigonella foenum-graecum, Foeniculum vulgare and Myristica fragrans. The major polyphenols and flavonoids quantified were gallic, protocatechuic, vanillic, syringic, para-coumaric, ferulic, rutin, trans-cinnamic, and quercetin. T. foenum-graecum FOs recorded high levels of ergosterol (48.56 mg/100 g) and stigmasterol (247.36 mg/100 g). The fucosterol levels were high in A. galanga (268.31 mg/100 g) FOs, whereas C. zeylanicum FOs showed high content of β-sitosterols (7037.77 mg/100 g). C. zeylanicum and T. foenum-graecum FOs recorded high α-tocopherol content (47.55 and 15.96 mg/100 g respectively). C. zeylanicum FOs showed high levels of three ferulates, namely, cycloartenyl ferulate, 24-methylene cycloartenyl ferulate and β-sitosteryl ferulate, whose contents were 89.42, 170.23 and 50.23 mg/100 g respectively which was confirmed by HRMS with a molecular mass (m/z) of 601.45, 615.47, and 589.45 respectively. Further, γ-oryzanol ferulates in C. zeylanicum FOs were confirmed by ¹H-NMR analysis. The acidified methanolic extractives of FOs showed high free radical scavenging activity and antioxidant potential. These spice FOs have excellent antioxidant activities, and are novel potential functional ingredients against lifestyle disorders.