Extraction, Purification And Anti-oxidation Of Proanthocyanidins From Rapeseed Shell

Proanthocyanidins (PC), also known as condensed tannins, are polymeric compounds, which are widely distributed in plant kingdom. It acts as an antioxidant, removes free radicals, and reduces risk of chronic diseases such as cardiovascular disease and cancer. Therefore in recent years much emphasis has been put on studies of proanthocyanidins which are mostly from grape seed and pine bark. But at present few reports are found on the research of the rapeseed shell proanthocyanidins (RSPC). This paper has studied the extraction, purification and anti-oxidation activity of RSPC, Research results are as follows:1) Rapeseed shell contains 11.72% water,9.23% protein,10.93% fat,3.76% tannins,2.45% phytic acid,10.89μmol/g glucosinolates, and 2.98% proanthocyanidins. The PC contents of free form, bounded with protein and fiber in the rapeseed shell were 1.52%,0.67% and 0.79% respectively. Therefore rapeseed shell can be considered as a new resource of proanthocyanidins.2) Based on single factor tests, the main factors affecting the extraction of proanthocyaindins were studied. Then a predictive polynomial quadratic model was set up by means of central composite design to optimize the extraction parameters of RSPC. The optimal conditions of extraction by ultrasonic wave were concluded as follows:granularity of rapeseed shell 60 mesh, concentration of ethanol 54%, solid-liquid ratio 1:12, pH 5.0, the time of ultrasonic treatment 23 min, extracting for 3 times. Under this condition, the extraction yield reached to 91.13%.3) After handling with 2 times volume of petroleum ether and 3 times volume of chloroform, the PC content reached to 56.75%. Experiments of 6 kinds of macroporous adsorption resin adsorbing and desorbing RSPC showed that HPD750 was the most appropriate resin in all for the preliminary purification of RSPC, the optimal condition of purification was:concentration of RSPC was 3 mg/mL, pH 5.0, the adsorptive velocity was 2 mL/min; ordinal elution with 90 mL 60% EtOH, desorptive velocity was 2 mL/min. Under this condition, the content of PC of the vacuum frozen drying products reached to 96.2%.4) Compared with Vc, RSPC has stronger capacity in the experiments on deoxidization capacity, savenging HO·,O2-·and DPPH·free radicals. Only in the experiment on inhibitory effects on the oxidation of liposome peroxidation system, the BHT showed a stronger capacity than RSPC. RSPC showed no significant difference with grape seed proanthocyanidins in the above experiements. All proved that the RSPC had strong anti-oxidation ability, and it is a kind of good and pure natral anti-oxidant.