Researches On Isolation,Purification And Bioactivities Of Sufu Peptides

In order to obtain the functional ingredients from sufu(the fermented soybean curd),we investigated the antioxidant components(peptides,isoflavones)and their relationship with antioxidant activities during the manufacturing of white sufu in this paper.On the basis of this,the peptides was extracted and purified from 45 days of sufu by water and then 80% ethanol,and their antioxidant activities and anticancer activities were subsequently confirmed by vitro experiment,which provided a theoretical basis for developing sufu functional products.Firstly,the samples of tofu(bean curd),pehtze,salted pehtze and those taken on day 15,30 and 45 from the dressing mixture were harvested for analysis.The changes contents of protein(including protein hydrosates)and isoflavones and their correlation with antioxidant activities were studied.The results showed that the protein gradually degraded into small molecule peptides and amino acids during the manufacture process of sufu,and the isoflavone glucosides were completely converted into aglycones.At the same time,the correlation analysis showed that the antioxidant activities(FRAP and ABTS)of sufu had a strong correlation with water-soluble protein,especially 500-1000 Da peptides(<0.01).Secondly,the water-isolating peptide fractions P1 and P2 were obtained by water extraction and purified by Sephadex G-15 from water protein extract(WP),while the ethanolextracting component EP was obtained from the water extaction residue with 80% ethanol.As a result,P1 and P2 contained more than 97% of protein(peptides),while the EP contained about 80% of peptides with 17.86% of fat.In addition,the isoflavone contents of P1 and P2 was less than that of EP,which was 2.09mg/g dry weight,1 to 1.5-fold higher than that of waterextracting component.After isolation and purification from WP,the antioxidant activities of P1 and P2 were enhanced,while EP was almost as strong as WP.Besides,P1,P2 and EP showed great inhibitory on MCF-7 and HepG2 tumor cells compared with normal cell LO2.After treated peptide solution(500 ?g/m L of P1,P2 and EP),the cell shrank and the chromosomal DNA of the nucleus was highly concentrated and agglomerated to produce apoptotic bodies.Finally,the molecular weight of the bioactive peptides were also identified by LC-MS.It was found that the highest peptide peak in P1 was 943.53 and the amino acid sequence was PheAsn-Lys-Thr-Ser-Ser-Phe-Asn.Another peptide peak with 2088.02 Da in EP was also identified as Val-Ser-Ile-Ile-Asp-Thr-Asn-Ser-Leu-Gle-Asn-Gln-Leu-Asp-Gln-Met-Pro-Arg.Thirdly,the water-extracting fraction DP1,DP2 and the ethonal extraction fraction DEP were obtained by two-step extraction of defatted sufu just as full-fat sufu.The main components and their antioxidant and anticancer activities were also analyzed.The results showed that the defatting treatment did not change the composition and bioactivies of the water-extrating peptide components(DP1and DP2).However,the bioactive components,antioxidant activities and the inhibitory on the tumor cells(HepG2 and MCF-7)of defatted ethanol extraction DEP were significantly decreased compared with EP.In addition,the LC-MS results indicated that the target peaks in defatted sufu peptides(DP1,DP2 and DEP)were enriched after defatting.At last,the peptides with molecular weights of 943.53 Da and 2088.02 Da were identified in DP1 and DEP,respectively,which were the same as P1 and EP.Finally,our studies demonstrated that sufu peptides have a significant correlation with antioxidant activities and the bioactive peptides obtained by different extraction methods have in vitro antioxidant activity and anticancer activity.