Studies On Antioxidant Properties And Structure Of Proanthocyanidins From Larch Bark

The influence of degrease by petroleum ether at extracting proanthocyanidins from larch bark was analysed, the extracts were then purified by macroporous resin, membrane filtration and solvent extraction, and antioxidant properties, stability and structure of proanthocyanidins from larch bark were also studied..Proanthocyanidins from larch bark was extracted by supercritical carbon dioxide fluid extraction (SFE) and ultrasonic-assisted extraction (UE), which has higher content of proanthocyanidins, total phenol, total flavonoids and yield. The contents were higher in UE than that of the SFE, and the contents of proanthocyanidins of defatted extracts were higher than the nondefatted extract. Moreover, the yield of the defatted extracts was lower than the nondefatted extract.The adsorption and desorption on4kinds of macroporous adsorption resins (AB-8, HPD-100, HPD-400A and HPD-700) were tested as a means of purifying the proanthocyanidins from crude extract of larch bark. Experiments results showed that AB-8resin was the best adsorbent resin. Kinetics of adsorption and isothermal adsorption curve was studied. Proanthocyanidins from larch bark was purified by nano filtration and ultrafiltration. The optimum technological condition by examining different molecular weight and input concentration was molecular weight cut off100000and input concentration was10mg/mL. The contents of proanthocyanidins, total phenol and total flavonoids from larch bark were improved by extracted with ethyl acetate.Scavenging DPPH radical activity and anti-lipid peroxidation of Proanthocyanidins from larch bark before and after purification were studied; the results showed that Proanthocyanidins from larch bark has high antioxidant properties. Scavenging DPPH radical activity and anti-lipid peroxidation were improved after the purified, and showed a high effect as compared to vitamin C. The stability of proanthocyanidins from larch bark was also studied under diffident temperature. pH. light and metal ions. The result showed that:Proanthocyanidins from larch bark was stable under a low temperature or acidic condition; light can make the content of Proanthocyanidins decreased, and the stability decreased with the increase of light intensity; the metal ion as Ba2+had the most preserving effect for the stability of Proanthocyanidins, although the metal ions as Cu2+, Fe3+and Fe3+had the most destructive effect for the stability.The structures of proanthocyanidins from larch bark were analysised by two-dimensional infra-red (2D IR) correlation spectroscopy and high-performance liquid chromatography (I IPLC).The result showed that the IR spectra of proanthocyanidins from larch bark were similar to the IR spectra of proanthocyanidins standard; proanthocyanidins from larch bark rich in catechins, and the constituents are very complex.