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Roselle (Hibiscus sabdariffa) Seed Oil Is a Rich Source of γ-Tocopherol

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ABSTRACT:  The antioxidant potential of roselle (Hibiscus sabdariffa L.) extracts was studied. Different plant organs, including seeds, stems, leaves, and sepals, were analyzed with respect to their water-soluble antioxidant capacity, lipid-soluble antioxidant capacity, and tocopherol content, revealing that roselle seeds are a good source of lipid-soluble antioxidants, particularly γ-tocopherol. Roselle seed oil was extracted and characterized, and its physicochemical parameters are summarized: acidity, 2.24%; peroxide index, 8.63 meq/kg; extinction coefficients at 232 (k232) and 270 nm (k270), 3.19 and 1.46, respectively; oxidative stability, 15.53 h; refractive index, 1.477; density, 0.92 kg/L; and viscosity, 15.9 cP. Roselle seed oil belongs to the linoleic/oleic category, its most abundant fatty acids being C18:2 (40.1%), C18:1 (28%), C16:0 (20%), C18:0 (5.3%), and C19:1 (1.7%). Sterols include β-sitosterol (71.9%), campesterol (13.6%), Δ-5-avenasterol (5.9%), cholesterol (1.35%), and clerosterol (0.6%). Total tocopherols were detected at an average concentration of 2000 mg/kg, including α-tocopherol (25%), γ-tocopherol (74.5%), and δ-tocopherol (0.5%). The global characteristics of roselle seed oil suggest that it could have important industrial applications, adding to the traditional use of roselle sepals in the elaboration of karkade tea.

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