The Antioxidant And Antiproliferative Activities Of Phenolics Extracted From Buckwheat

Phenolic compounds extracted from hulls, brans and flours of Fagopyrum esculentum Moench and Fagopyrum tartaricum L. Gaerth were screened for the content and antioxidant activity. On the basis of the above considerations, the composition, cellular antioxidant activities and antiproliferative activities of phenolic compounds extracted from two tartary buckwheat brans were investigated.(1) The extracts from hulls, brans and flours of ten buckwheat(Fagopyrum esculentum Moench three varieties and Fagopyrum tartaricum L. Gaerth seven varieties) were screened for free and bound phenolic content or total phenolic content (TPC), as well as1,1diphenyl-2-picryl hydrazyl (DPPH) free radical scavenging activity and reducing power. The results indicated that free phenolics were the predominant form in buckwheat hulls (the percentage of free phenolic to total phenolic was79.7%), brans (the percentage of free phenolic to total phenolic was92.89%) and flours (the percentage of free phenolic to total phenolic was94.07%); The content and antioxidant activit of phenolic extracted from Fagopyrum tartaricum L. Gaerth were generally higher than that of Fagopyrum esculentum Moench. Fagopyrum tartaricum L. Gaerth brans had the highest average TPC (24.87mg GAE/g dwb); Buckwheat hull and bran showed higher phenolic content and antioxidant activity than buckwheat flour.(2) RP-HPLC-DAD/ESI-TOF-MS was used to identify phenolic compounds in Fagopyrum tartaricum L. Gaerth bran harvested from Youyang County, Chongqing municipality (FGl) and Xichang City, Sichuan province (FG2). Thirteen phenolic compounds were detected both in FG1and FG2, including catechins,(-)-epicatechin-3-(3"-O-methyl) gallate, caffeic acid hexose, protocatechuic acid, catechin-glucosidederivatives, vitexin, chlorogenic acid, dicaffeoylquinicacid derivatives,3-O-methylgallic acid, myricetin, rutin, isoquercitrin and quercitrin. The result is that flavonoids were the main phenolic compounds of tartary buckwheat bran.(3) The phenolics extracted from FG1and FG2brans were evaluated by oxygen radical absorbance capacity (ORAC) and cellular antioxidant activity (CAA) assays. Both of free and bound phenolic extracted from FGl and FG2exhibited potent chemical antioxidant activity, and the ORAC value of FG2(106.8±0.2μmol TE/g DW) was higher than that of FG1(75.3±5.8μmol TE/g DW)(p<0.05)。However, only the free phenolics showed effective cellular antioxidant activity and the CAA valuse of FG1and FG2were34.5±1.8μmol of QE/100g and46.4±5.8μmol of QE/100g respectively(PBS wash);39.8±2.4μmol of QE/100g and53.8±2.5μmol of QE/100g respectively (PBS no wash).The bound phenolics showed no cellular antioxodant activity within non-cytotoxic concentrations.(4) The phenolics extracted from FG1and FG2brans showed potent anti-proliferative activity against human liver cancer cells (HepG2) and human colon cancer cells (Caco-2) within non-cytotoxic concentrations in a dose-dependent manner. In the antiproliferative experiment of HepG2cells, the EC50values of FG1and FG2were16.2±0.2mg-mL"1and17.4±0.2mg-mL-1respectively; In the antiproliferative experiment of Caco-2cells, the EC50values of FGl and FG2were22.3±0.4mg-mL-and14.5±0.2mg-mL-1respectively. The result indicated that the free phenolics of FG1and FG2exhibited significantly inhibitory effects against HepG2and Caco-2cells. To the contrary, the bound phenolics of FG1and FG2did not show inhibitory effects against HepG2cells or show weak inhibitory toward Caco-2cells within non-cytotoxic concentrations.