Roselle (Hibiscus sabdariffa) seed oil is a rich source of gamma-tocopherol

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 gamma-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 (k(232)) and 270 nm (k(270)), 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 beta-sitosterol (71.9%), campesterol (13.6%), Delta-5-avenasterol (5.9%), cholesterol (1.35%), and clerosterol (0.6%). Total tocopherols were detected at an average concentration of 2000 mg/kg, including alpha-tocopherol (25%), gamma-tocopherol (74.5%), and delta-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.