Study On Extraction,Antioxidantion And Antibacterial Activity Of Polyphenols From Fruit Shell Of Carya Cathayensis

The fruit shell of Carya cathayensis is the by-product in Carya cathayensis processing. The majority of them are burnt or abandoned in actual production, which result in great pollution and waste. In recent years, some studies indicated that the phytochemicals in the fruit shell of Carya cathayensis are polyphenols, flavonoids, alkaloids, et al. But, there are almost no reports about the extraction of the active ingredients of the fruit shell of Carya cathayensis and its biological activity. Therefore, it is very meaningful to study the optimization extraction of polyphenols and its antioxidant and antimicrobial activties. The major findings were presented as follows:(1) This paper studied the influence of factors of solvent-material ratio, ethanol concentration, microwave power, microwave time on the yield of polyphenols. Based on single-factor experiment, the method of response surface analysis with3factors on the yield of polyphenols was adopted. The model obtained produced a satisfactory fitting of the experimental data with regard to polyphenols extraction (R2=0.969, P<0.01). The optimal conditions of microwave-assisted extraction were as follows:ethanol concentration56.0%, solvent-material ratio1:50, microwave power500W and time100S; the theory value of polyphenols was125.60mg/g, and the actual value of polyphenols was123.41mg/g. It showed a accuracy and reliability model.(2) The present study was designed to explore the antioxidant potential of petroleum ether, chloroform, ethyl acetate, n-butanol and water fractions of80%methanol extract of the fruit shell of Carya cathayensis by reducing power, DPPH·, hydroxyl radicals(·OH) and superoxide radicals(O2-·) assays. The results indicate that ethyl acetate fraction richest in phenolic and flavonoid contents had potent antioxidant activity in comparison with other fractions and the positive control (BHT).These findings have also shown excellent correlations between antioxidant activity and total phenolic contents and the correlation coefficients were r=0.895for RP; r=0.969for DPPH·; r=0.917for·OH; r=0.960for O2-· Hence, ethyl acetate fraction represents a source of potential antioxidants that could be used in pharmaceutical and food industry. (3) This paper studied the inhibition effects and stability of supercritial fluid extract from fruit shell of Carya cathayensis against5common food spoilage bacteria such as Staphylococcus aureus, Escherichia coil, et al. The results showed supercritial fluid extract had great inhibition effects against bacteria, and the extractive exhibited higher antibacterial activity against gram-positive bacteria than gram-negative bacteria. The effects to Staphylococcus aureus was the most significant, the MIC value and MBC value were3.125mg/mL and6.25mg/mL. Under slightly acidic condition or with Na2SO3synergistic effect, it would enhance its antibacterial effect; high temperature treatment could weaken antibacterial ability; the UV irradiation was almost no influence on it.