Extraction, chemical characterization, in vitro antioxidant, and antidiabetic activity of canola (Brassica napus L.) meal

Canola (Brassica napus L.) meal is a by-product after oil extraction from canola seed and is of relatively low value. This meal may have additional value in the biotechnology, food, and pharmaceutical industries if health-promoting useful bioactive compounds can be identified. Hence, seven canola meal extracts (CMEs) were generated using different organic solvents for two genotypes. HPLC and LCMS analyses were employed for the determination of the phenolic and antioxidant activity of meal extracts, including recovery of major biological compounds. When comparing genotype-1 with genotype-2, the latter had higher antioxidant activity in acetone extract (AE). This study also indicated seven major glucosinolates in CMEs in which water (WE) appeared to be the best solvent for the recovery of glucosinolates. Higher quantities of phenolic, glucosinolate, and antioxidant were present in genotype-2 compared with genotype-1. Using HPLC-DAD and LC-MS analysis 47 compounds were detected. We could identify 32 compounds in canola meal extracts: nine glucosinolates and twenty-three phenolic derivatives. Phenolic compounds in canola meal were conjugates and derivatives of hydroxycinnamic acid (sinapic, ferulic, and caffeic acids). Among phenolics, kaempherol as conjugate with sinapic acid was found; sinapine and trans-sinapic acid were the most abundant, as well as major contributors to the antioxidant and free radical scavenging activities of canola meal extracts. Some samples exhibited mild to moderate in-vitro antidiabetic activity in a Dipeptidyl Peptidase-IV inhibition assay.