Separation, Purification And Characteristics Of Active Compounds Anthocyanins And Caffeoyl Conjugates In Purple Sweet Potato

In this experiment, we take the root of purple sweet potato Ayamurasaki as experimental material, and used microwave baking (MB) and acidified electrolyzed water (AEW) solution as the extraction solvent to get the crude extracts. We isolated and purified the crude extracts by means of macroporous resin (AB-8) adsorption, following ethanol-water eluting and got the purified extracts of purple sweet potato (PSP). Anti-tumor activity tests in vivo showed that the purified extracts can inhibit the growth of S180sarcoma in mice; the highest inhibition rate was close to80%. Besides that, purified extracts have strong protective effects on acute ethanol-induced liver injury in mice. Treatment with different doses of extracts could significantly decrease serum ALT, AST levels and increase liver SOD, GST, CAT and GSH levels of model mice. It indicated that the purified extracts of PSP may protect liver from suffering ethanol disease by increasing antioxidant capacity.We isolated and purified the main compounds from purified extracts by pre-preparative HPLC, and obtained ten compounds, Which including five red compounds and have strong absorbance at vis-spectrum530nm. According to the spectrum data of molecular ion peak and molecular fragments peak by MS and relevant reports, we inferred the5compounds were acylated cyanidin or peonidin glucoside compounds, which were cy-3-(6’’,’’’-dicaffeoylsoph)-5-glcc; cy-3-(6’’-caffeoyl-6’’’-feruloylsoph)-5-glcc; pn-3-(6",6"’-dicaffeoylsoph)-5-glcc; pn-3-(6’’-caffeoyl-6’’’-p-hydroxybenzoylsoph)-5-glcc; pn-3-(6’’-caffeoyl-6’’ feruloylsoph)-5-glcc. Those5anthocyanins compounds have different color values. Pn-3-(6"-caffeoyl-6"’-feruloylsoph)-5-glcc got the highest value that was147at530nm. It indicated that this compound was the most reddest, which has high reference value for new cultivar of purple sweet potato as green healthy food coloring.With LC-MS,1H-NMR and13C-NMR, the composition and structure of5non-red compounds were analyzed. We identified it as caffeoyl compounds, containing caffeoylquinic acid caffeoyl diglucoside compounds. According to previous reports,5-caffeoylquinic acid,3,5-dicaffeoylquinic acid and4,5-dicaffeoylquinic acid were combined with anthocyanins in purple sweet potato, but no separated structures. Whereas6-O-caffeoyl-β-D-fructofuranosyl-(2-1)-α-D-glucopyranoside and trans-4,5-dicaffeoylquinic acid were found in purple sweet potato Ayamurasaki for the first time.Antioxidant assay in vitro showed5caffeoyl compounds got the highest antioxidant activities, anthocyanins next, and thirdly purified extracts of purple sweet potato. The DPPH radical scavenging assay indicated these samples had strong scavenging activity. Their inhibition rates (IC50) were7.6μg/ml to12.4μg/ml.To sum up, the active compounds extracts of purple sweet potato had strong anti-tumor and liver protecting effect. Five red anthocyanins and five non-red caffeoyl compounds were identified through further purified and separated, and caffeoyl compounds had much stronger antioxidant activities and DPPH radical scavenging activity than others. Those results above in this paper is aimed at laying the groundwork for progress at purple sweet potato or its extracts as healthy food and green food coloring, healthy food and active compounds. Also it can provide basis of new functional breeding of purple sweet potato.