Study On The Purification And Properties Of Procyanidins From Peanut Skins

Peanut skins,a byproduct of peanut oil and protein processing,are rich in procyanidins.And the chemical composition of procyanidins from peanut skins are different with that of grape seeds,which might provide a breakpoint for the development of procyanidins products in peanut skins.Focusing on the purification,chemical composition and functional evaluation of procyanidins in peanut skins,main research contents are shown as follows:Firstly,optimization of procyanidins purification from peanut skins by macroporous adsorption was done.At the same time,the residual amount of AFB1 in procyanidins products was determined with high performance liquid chromatography-mass spectrometry/mass spectrometry(HPLC-MS/MS).Based on adsorption rate,desorption rate and static adsorption kinetics of the resin,AB-8 resin was selected as the adsorption material for procyanidins preparation in peanut skins.The optimum purification conditions were 0.5 mL/min of sample loading flow rate and 1.0 mL/min of desorption flow rate.And the best eluent was 20% and 40% ethanol solution.The result showed that the purity and recovery rate of procyanidins in peanut skins eluted with 20% ethanol were 98.19±1.66% and 29.41±0.64%,respectively.And there was no AFB1 was detected.The purity and recovery rate of procyanidins in peanut skins eluted with 40% ethanol elution was 86.17±0.64% and 50.31±1.15%,respectively.The content of AFB1 was 3.6 ?g/kg.Both the content of AFB1 were much lower than the national standard(20 ?g/kg).Secondly,the chemical composition of procyanidins in peanut skins was determined with ultra performance liquid chromatography-quadrupole-time of flight-mass spectrometry(UPLC-Q-ToF/MS).The result showed that: 20% ethanol elution of procyanidins in peanut skins mainly consisted of three B-type dimers,two A-type dimers and five A-type trimmers,the proportion of them were 7.54%,41.72% and 50.73%,respectively.And 40% ethanol elution of procyanidins in peanut skins mainly consisted of three A-type dimers,three A-type trimmers and a A-type tetramer,the proportion of them were 51.73%,29.57% and 18.71%,respectively.Main components of procyanidins in peanut skins were A-type dimers and A-type trimers,the monomer of which were catechin and epicatechin.The procyanidins in grape seeds contained monomers,B-type dimers and B-type trimers.The monomer of them were(epi)catechin and their gallate.The polymerization degree of procyanidins from both peanut skins and grape seeds was below 3,which meant that it can be absorbed by human gastrointestinal tract easily.Finally,the functional properties of procyanidins in peanut skins were studied,compared with commercially available grape seeds procyanidins.The conclusion was that: the water solubility of procyanidins in peanut skins was 8.75% higher than that of commercially available grape seeds procyanidins.Procyanidins in peanut skins were insensitive to light and stable under weak acid conditions,and can exist with sodium benzoate and other commonly food additives,but are sensitive to temperature and unstable under alkaline conditions.It can react with Cu2+,Fe2+ and Fe3+ to produce flocculent precipitation.Generally procyanidins of peanut skins are more stable than that of grape seeds.The ORAC,ABTS,DPPH and FRAP values of the procyanidins in peanut skins were 12.42,8.65,7.29 and 3.82 mmol TE/g PC,respectively.The ORAC,ABTS,DPPH and FRAP values of the grape seed procyanidins were 11.35,7.91,7.34 and 4.31 mmol TE/g PC,respectively.The results showed that ORAC and ABTS methods were consistent with DPPH methods.No significant difference was shown between the two groups(p>0.05),while the FRAP showed there are significant differences between the two groups(p<0.05),the antioxidant activity of the former was lower than that of the latter.The results of cellular antioxidant activity assay(CAA)showed that the EC50 values of procyanidins in peanut skins and grape seeds were 24.90 ?g/mL and 19.29 ?g/mL,respectively,no significant difference was shown between the two groups(p>0.05),and the CAA activity of the two were similar.