Conyza canadensis: Green Extraction Method of Bioactive Compounds and Evaluation of Their Antifungal Activity

Synthetic fungicides are a common treatment for post-harvest diseases in fruits, although demand is increasing for alternatives such as biopesticides. The aim of this work was to investigate the presence of naturally occurring antifungal compounds in Brazilian specimens of the weed Conyza canadensis. Two compounds [(4Z)-lachnophyllum lactone and (4Z, 8Z)-matricaria lactone] were isolated and their antifungal activities were evaluated against eight postharvest disease fungi. Aspergillus niger, Cladosporium sp., and Penicillium digitatum proved susceptible to the treatment (minimum inhibitory concentrations varying from 32 to 64 mu g mL(-1)). These fungi are common postharvest pathogens of fruits and vegetables, causing rots and secreting mycotoxins. A green and sustainable extraction method employing pressurized hot water was developed and optimized (100 degrees C, 4 x 1 min cycles). Yields of 1.46 and 0.24 mg g(-1) were obtained for (4Z)-lachnophyllum lactone and (4Z, 8Z)-matricaria lactone, respectively. The extract could be applied directly to fruits and vegetables in postharvest treatments.