Study On Extraction, Purification And Activity Of Phenolics From Rapeseeds

Rape of cruciferous crops, is the world’s third-largest oil crops, which is widely distributed in China, as well as Canada, India, Poland, France, Pakistan, and other countries. Acreage of rape in China is more than7million hectares, and output has been up to more than12million tons, ranking the first in the world. The industrial application in comprehensive utilization of rapeseed is not enough. For the human demand, more scientific researches of comprehensive utilization of rapeseed are needed. The phenolics extraction of rapeseed was studied in this article, with the optimal extraction process of phenolics from rapeseed determined; the best purification condition of macroporous adsorption resins of phenolics from rapeseed was studied in order to improve the purity of phenolic material of rapeseed. In vitro antioxidant activity of phenolic compounds of rapeseed was invaluated. In addition, inhibition of phenolic compounds of the rapeseed on plant pathogenic bacteria (Rhizoctonia cerealis, Alternaria sonali, Ahernaria brassicae) was also determinated, and their minimum inhibitory concentration was received. The main studies are as follows:(1) The optimum extraction process of phenol extraction from rapeseed was studied. Whole rapeseed was broken as raw materials. In the base of single factor experiments, four factors (ethanol concentration, extraction time, temperature, and times) which exerted larger effects on phenol extraction were filtered out by Plackett Burman test. Response surface analysis was used to optimaze extraction process and got the best extraction parameter:ethanol concentration was65%; extraction temperature was70℃; extraction time was50min; ratio of sample to solution was1:8(m:v); hydrochloride content was0.04%; oscillator speed was200r/Min; and extracted for3times. After optimization, the rate of phenolics extraction was75.39%, close to the result of predictive models, which provided theoretical basis for phenolics extraction of rapeseed.(2) The best purification conditions of rapeseed phenolic compounds were studied. Filter test of eight kinds of different types of macroporous resin proved that HPD100with strong adsorption and desorption capacity on rapeseed phenolics, was suitale to apply to purification of phenolics from rapeseed. The optimum conditions of adsorption and desorption was determined by study of HPD100dynamic curve of adsorption and desorption on rapeseed phenolics:loading solution concentration was3.5mg/mL; injection velocity was3mL/min; volume fraction of ethanol was60%; elution speed was2mL/min; and elution volume was100mL. After purification, the purity of rapeseed phenolics increased from3.79%to35.48%. It indicated that HPD100macroporous resin was better in purification of phenolics from rapeseed than others, which could significantly increase the purity of the extraction phenolics.(3) In vitro antioxidant activity and antimicrobial activity of phenolic compounds were studied. The antioxidant activity of rapeseed phenolics was determined by the reducing capacity, ability of scavenging ABTS+·free radical,ability of scavenging DPPH free radical, and ORAC methods. Reducing capability increased according to the concentration of phenolics,When the concentration was about45ug/mL, rapeseed phenolics redecring capacity was equal to Vc. Scavenging ability of rapeseed phenolics on ABTS+·,DPPH free radical enhanced with the increase of the concentration. Under the same concentration, scavenging ability of rapeseed phenolics on ABTS+·, DPPH free radical were lower than Vc. The ORAC value of rapeseed was2.26mmol trolox/g DW, and its total antioxidant activity was lower than that of tea. This showed rapeseed phenolic compounds possessed moderate antioxidant capacity, with potential application prospects.Rapeseed phenolics had the certain inhibition on phytopathogenic bacteria, and inhibitory effects remarkably increased with the increase of concentration. The minimum inhibitory concentration (MIC) of rapeseed phenolics on Alternaria sonali was around0.8mg/mL; MIC on Rhizoctonia cerealis was around0.6mg/mL, and MIC on Ahernaria brassicae was around1.5mg/mL. When the concentration of rapeseed phenolics reached6mg/mL, the inhibition rates on three kinds of phytopathogenic bacteria were over80%. This provided a new aspect for the development of biological pesticides.