Concurrent extraction and transformation of bioactive phenolic compounds from rapeseed meal using pressurized solvent extraction system

Sinapoylcholine (sinapine), rich in rapeseed (Brassica napus L) meal, can be hydrolyzed into sinapic acid and further transformed into canolol under proper circumstance. These sinapic derivatives are excellent bioactive compounds. This work thus reported a novel approach by means of pressurized solvent extraction (PSE) that enables a simultaneous efficient extraction and transformation of sinapine into canolol. With the total phenolic yield and DPPH scavenging activity of the extract as indexes of extraction efficiency, operation time/temperature and solvent property/dosage were found to have profound effects. The transformation of sinapine to canolol was largely governed by the operational temperature and NaOH concentration in solvent. The best extraction efficiency (92.53 and 66.68 mg sinapic acid equivalent/g rapeseed meal in terms of total phenolic yield and DPPH scavenging activity) was achieved with 60% methanol, 200 degrees C, and residence time 20 min, which was of >300% of the Soxhlet extraction (100 degrees C for 12 h). The maximal yield of canolol (7.23 mg/g rapeseed meal) was obtained with 100% methanol, 200 degrees C, and 5 min with addition of 1% NaOH in methanol (w/v). This study demonstrates that PSE could be an effective approach that enables both extraction and transformation of phenolic compounds in rapeseed meal; which might find general application in extraction and transformation of natural bioactive compounds from agricultural residues. (C) 2016 Elsevier B.V. All rights reserved.