PROANTHOCYANIDIN MICROCAPSULES - PREPARATION, PROPERTIES AND FREE-RADICAL SCAVENGING ACTIVITY

Microcapsules were prepared by interfacial cross-linking of grape proa nthocyanidin (GPO) with terephthaloyl chloride (TC). Using 5% TC, 30-m in reaction time and a stirring speed of 5000 rpm, batches were prepar ed from 10% GPO solutions in buffers pH 8, 9.8, and Il, respectively. Microcapsules were studied with respect to morphology (microscopy), si ze (laser diffraction technique), stability in water at 45 degrees C a nd, for stable batches, IR spectroscopy, degradation in human plasma, and free radical scavenging activity studied by electron paramagnetic resonance (EPR) using both extinction of the stable radical DPPH (2, 2 -diphenyl-picryl-hydrazyl), and scavenging of OH degrees (evaluated us ing 5,5-dimethyl-pyrrolidine-N-oxide; DMPO). All particles had a mean size < 10 mu m. Microcapsules obtained at pH 8 were unstable (yellow s upernatant after 8 days). Microcapsules obtained at pH 9.8 and 11 exhi bited a high stability (> 5 months). Using a stirring speed of 3000 rp m at pH II provided 15-mu m particles which gave a yellow supernatant after 3 weeks. The IR spectra of the two stable batches (pH 9.8 and 11 ) showed bands at 1736 and 1267 cm(-1) reflecting the formation of est ers. They were slowly degraded in plasma, and although less active tha n the initial GPO, they exhibited a significant antioxidant activity. The method appears to be an efficient means of stabilizing the polyphe nol without suppressing the free radical scavenging activity. (C) 1998 Elsevier Science B.V. All rights reserved.