Abstract:

Pyroligneous acids were prepared throngh pyrolysis of apple tree branch at 3 temperature ranges. Chemical components of the pyroligneous acids were analyzed with GC-MS. Antimicrobial and antioxidant activities of the acids were tested. The results showed that pyroligneous acids derived with 3 temperature ranges were slightly different in chemical compositions, but significantly different in the contents of each chemical component. A total 45 compounds were identified from the pyroligneous acid collected from lower temperature range, 100～200 ℃ (AP₁), accounting for 91.26% of the total peak area. Phenols, organic acids, ketones, and furan derivatives in the pyroligeneous acids accounted for 51.33%, 18.50%, 8.98%, and 7.23%, respectively. A total 47 compounds were identified from the middle temperature range, 200～310 ℃ (AP₂), accounting for 95.35% of the total peak area. Their phenols, organic acids, ketones, and furan derivatives accounted for 24.69%, 40.05%, 7.52%, and 12.81%, respectively. The pyroligneous acids from the high temperature range, 310～500 ℃ (AP₃), had 47 compounds identified, accounting for 93.00% of the total peak area. Their phenols, organic acids, ketones, and furan derivatives accounted for 34.66%, 28.37%, 12.49%, and 6.93%, respectively. Organic acids had the highest content in AP₂, while phenols had the highest content in AP₁. All the pyroligneous acids from 3 temperature ranges exhibited antimicrobial and antioxidant activities, with different strengths. The antimicrobial activities of three pyroligneous acids were in an order of AP₂＞AP₃＞AP₁. AP₂ exhibited the strongest antimicrobial activity, significantly different from AP₃ and AP₁, and the range of EC₅₀ to plant pathogens was 2.43～5.27 mg·mL^-1. Antioxidant activities of three pyroligneous acids were all higher than those of BHT and ascorbic acid, and were in an order of AP₁AP₃＞AP₂ There existed a significant dose-effect relationship in the antioxidant activity. High antimicrobial activity of AP₂ and high antioxidant activity of AP₁ might be related to their high contents of organic acids and phenolic compounds respectively.

Key words: apple tree branch, pyroligneous acid, chemical component, antimicrobial activity, antioxidant activity