Evaluation of Chemical, Nutritional and Antioxidant Characteristics of Roselle (Hibiscus sabdariffa L.) Seed

Background and Objectives: Roselle (Hibiscus sabdariffa L.) is one of the valuable plants grown in tropical and subtropical regions such as some parts of Iran. Roselle calyces are commonly used to make  herbal tea as well as a natural food color additive. However, Roselle seeds are usually discarded as by–products, while they can be used as a source of nutritious and functional compound. Therefore, in the current study, some of the chemical and nutritional characteristics of Iranian Roselle seed were investigated. In addition, the effects of different extracting solvents on seed extraction yield, total phenol content (TPC) and antioxidant activity (scavenging ability) of the extracts were evaluated. Materials and Methods: Some chemical and nutritional properties of Roselle seeds such as moisture, protein, total fiber and lipid contents were determined. Also, fatty acid composition of the oil was determined using gas chromatography. The effects of different solvents including acetone, methanol and water, on yield, TPC (Folin–Ciocalteu assay) and antioxidant activity (DPPH and ABTS methods) of Roselle seeds were also investigated. Results: The results showed that the Roselle seeds are the main sources of protein, lipid and fiber (26.62±0.03%, 21.03±0.02% and 19.81±0.01%, respectively). Linoleic (41.06±0.7%), oleic (27.07±0.01%) and palmitic (21.9±0.03%) acids are the main fatty acids in the Roselle seeds oil. The maximum yield (20±0.02%), related to aqueous extract, however, higher TPC (201±0.02 mg GAEs/100 g) and antioxidant activity (DPPH, 94.15±0.2%; ABTS, 75.91±0.03%) were observed in acetone extract. Conclusions: According to the results, Roselle seeds are a good source of protein, fiber and oil, which contains unsaturated fatty acids especially linoleic acid. In addition, the acetone extract showed the highest TPC and antioxidant activity among other extracts.