Research On The Detection Method And Stability Of Resveratrol And Polydatin In Peanut

As a kind of polyphenolic substances, resveratrol is found as a plant antitoxin in grapeplants initially. Resveratrol was considered as one of the most effective anti-aging substancesin1998, which has significant antioxidant, anti-tumor effect, cardiovascular protection effectand phytoestrogens. Resveratrol is rich in polygonum cuspidatum, grapes, peanuts and otherplants.There are four main forms of resveratrol: cis-resveratrol,trans-resveratrol,cis-polydatinand trans-polydatin.Its thermal instability and photo instability limite its pharmacologicaleffects. This paper focuses on the content of four existing forms of resveratrol in peanuts andpeanut products and investigates its optical and thermal stability.First, the method of solid-phase extraction column pretreatment was optimized and ahigh-performance liquid detection method of resveratrol and polydatin was established inpeanut samples. Solid phase extraction column filler, solvent extraction and HPLC elutiongradient optimization were optimized. Solid phase extraction column was C18and Al2O3mixed filler, and the best ratio was1:1; extraction solvent was80%ethanol solution.Underthese conditions,the recoveries of trans-resveratrol, cis-resveratrol, trans-polydatin andcis-polydatin were95.7%,93.4%,97.6%and107.4%. Flow rate was0.5mL/min; detectionwavelength was285nm and308nm; column temperature was30℃; mobile phase A wasultra pure water and acetic acid (94:6), mobile phase B was acetonitrile.The separation carriedout with16%B for13min, and then the column was flushed with a7-min gradient to32%B,and then turned to80%B for4min, keep for6min, turned to16%B for3min,the initialconditions were then restablished for2min before another sample was injected.Under thiscondition, best separation of the four targets was obtained.Second, on the basis of the detection method which has been established, the contents ofpolydatin and resveratrol were investigated in parts of peanut varieties,commercial peanutbutter and peanut oil.The results showed that total resveratrol was ranged from0.164μg/g to1.866μg/g in18kinds of peanut.Trans-resveratrol and trans-polydatin were detected in allpeanut varieties, polydatin content was greater than resveratrol in most of the peanutsvarieties.Cis-resveratrol and cis-polydatin were detected in only a small portion of peanutvarieties.The content of total resveratrol in peanut butter was significantly higher thanresveratrol in peanuts, its range was from1.492μg/g to1.912μg/g, the reason for thedifference was estimated to the moisture content difference and the peanut skin of peanutsamples. The content of cis-resveratrol and cis-polydatin in peanut butter were higher thanthat in peanut. There were certain factors that made resveratrol and polydatin cis-transisomerization occur. The content of total resveratrol was ranged from0.114μg/g to0.526μg/g in peanut oil, its content was less than the total overall scope of resveratrol in peanuts.Refining peanut oil did not contain resveratrol and polydatin.Each step of refining had a lossof resveratrol, and after sweetening the resveratrol disappeared.Third, resveratrol and polydatin’s storage stability at different temperatures wasstudyed, the results showed that cis-resveratrol, trans-resveratrol, cis-polydatin andtrans-polydatin had different thermal instability, in which the stability of trans-resveratrol and trans-polydatin was higher.Stored for ten days at60℃, its content changed to95%of theoriginal. Cis-resveratrol and cis-polydatin had poorer light stability. Stored for ten days at60℃, its content became to60%-80%.Fourth, resveratrol and polydatin’s stability under different illumination wavelengths ofultraviolet light was analysisd.The results showed that there was big different influence usingdifferent wavelengths of UV light. After365nm UV irradiation, the total amount ofresveratrol and polydatin remained unchanged, only the cis-trans isomerization occurred. Bothconversion rates of trans-resveratrol and trans-polydatin were higher than cis-resveratrol andcis-polydatin. After254nm UV irradiation, the cis-trans isomerization occured and the totalresveratrol reduced.After254nm UV irradiation, three new substances were produced inresveratrol solution and two new substances in glycosides solution. After254nm UVirradiation, three new substances produced by resveratrol were:3,4’,5-trihydroxy-diphenylacetylene, resveratrol oxidation products and resveratrol dimer.After254nm UV irradiation,polydatin transformed into2,5′,7-trihydroxy-phenanthryl-beta-D-glucopyranoside and2,5′,7-trihydroxy-diphenylacetylene-beta-D-glucopyranoside.