Chemical Compositions and Biological Activities of Pyroligneous Acids from Walnut Shell

Seven kinds of pyroligneous acids were collected at different temperature ranges (K7-1: 90 to 140 ºC; K7-2: 140 to 190 ºC; K7-3: 190 to 240 ºC; K7-4: 240 to 290 ºC; K7-5: 290 to 340 ºC; K7-6: 340 to 440 ºC; and K7-7: 440 to 480 ºC). The chemical compositions of the pyroligneous acids were determined by GC-MS. Moreover, the biological activities of pyroligneous acids were investigated by a foliar spray experiment of rape using the pyroligneous acids collected at 90 to 480 ºC. The physiological and chemical responses of pyroligneous acids, including the content of soluble protein and the superoxide dismutase (SOD) activity, were detected. The results of GC-MS analysis showed that the chemical profiles of pyroligneous acids varied with pyrolysis temperature. About 62 kinds of compounds belonging to 8 groups were identified, including ketones, phenols, organic acids, ester, benzene and its derivatives, aldehydes, alcohols, and sugar derivatives. Finally, the pyroligneous acids from walnut shell were applied in foliar spray for rape (Brassica campestris L.). The results demonstrated that pyroligneous acid from walnut shell with a low concentration significantly enhanced the content of soluble protein and the activity of SOD in rape leaves.