Biological Activities And Chemical Profiles Of Pyroligneous Acids From Walnut Shell

Biological activities and chemical profiles of pyroligneous acids from walnut shell were investigated. Seperation technology of organic acids and phenols contained in pyroligneous acids was conducted. Attempts were made to further separate phenols by chromatographic method. The results were reported as follows:(1) Three kinds of pyroligneous acids were prepared from walnut shell at different temperature ranges (90–150°C, 151–310°C, 311–550°C). The antioxidant activities and chemical profiles of the acids were investigated respectively. The results showed that the chemical constituents of pyroligneous acids were similar, mainly phenols, organic acids, ketones, and furan derivatives. However, the contents of each constituent in three acids varied. All the pyroligneous acids exhibited antioxidant activity, but with different levels. The acid collected from311-550°C had the highest relative content of phenolic showing the strongest antioxidant activity.(2) Taking the pyroligneous acids collected from the whole temperature ranges as materials, methods of separating organic acids and phenols were probed by extraction method based on the differences of acidity between these two groups of components in the acids. Optical solvents used in the extractions were obtained. Antimicrobial and antioxidant activities of the fractions were examined to provide supplemental evidence for the separations. It was found that ethyl acetate was a satisfactory solvent to enrich all th organic components from the pyroligneous acids. The fraction extracted by 5% NaHCO3 had a high content of organic acids and exhibited the highest antimicrobial activity with the inhabiting rate more than 90% to Alternaria solani, Botrytis cinerea and Glomerella cingnlata. When the concentration of this extract was 20mg?mL-1, its inhabiting rate was up to 50% to Alternaria solani, Verticillium dahliae, Botrytis cinerea and Glomerella cingnlata and their EC50 were 10.7529, 16.3994, 9.5618 and 18.5111 mg?mL-1, respectively. When the concentration decreased to 5 mg?mL-1, it had strong antibacterial activity to Bacillus subtilis, Bacterium prodigious sand Staphylococus aureus and their diameter of the inhabited rings were 16.00mm, 15.33mm and 10.17mm, separately. While the concentration increased to 20 mg?mL-1, its antibacterial activity was enhanced, the diameter of the inhabited rings were more than 20mm. After the pyroligneous acids were ectracted by 5% NaHCO3, the optimal solvent to extract organic acids, the moter liquid was further subjected to extraction by Na2CO3 and NaOH with different basicities to extract phenols. Every fraction showed a certain degree of antibacterial activity. And the optimal solvent was 4% NaOH, which had the highest content of phenolic compounds (1334.374 mg/L), 1.64 times more than that of the mother liquid. The antioxidant activity of the four fractions was positively correlated with the content of phenolic compounds. Their values of scavenging activities of DPPH were higher than 85%. And when the equivalent concentration of FeSO4 was 45.30mg/L, their inhibitory rates on linoleic acid oxidation were up to 91.02%. On the other hand, the fraction extracted by 6% NaOH solution had the strongest reducing power to molybdenum ions and the content of active compounds of 1g sample was equal to 1424mg ascorbic acid. The fraction extracted by 4% NaOH solution was further purified by chromatographic method.The fraction F1 had the highest content of phenolic compositions and strongest antioxidant activity among the four fractions collected, stronger than those of mother liquid.