Chemical composition, nutritional value and antioxidant properties of Allium cepa L. Var. tropeana (red onion) seeds

Chem. anal. of Allium cepa L. var Tropeana (red onion) seeds showed high amts. of oil (20.4%), fiber (22.4%), crude protein (24.8%), calcium (175.0 mg/100 g), potassium (1010 mg/100 g), low amts. of sodium (11.2 mg/100 g) and 6 cysteine derivs., of which the S-propylmercapto-cysteine has never been reported in onion before. The antioxidant capacity of seed exts. contg. cysteine derivs. (SECCD), before and after boiling the seeds, and of cooking water exts. contg. cysteine derivs. (CWECCD), was also evaluated, by the ferric reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picrilhydrazyl (DPPH) assays. The exts. showed discrete antioxidant capacity which increased after boiling, although cooking methods caused significant losses of the cysteine derivs. in water.