Abstract
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 µg 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 °C, 4 × 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.
Highlights
Postharvest diseases are the main factors responsible for fruit losses along the production chain.[1,2] These diseases are usually caused by fungal pathogens that are commonly controlled by the application of synthetic fungicides.[3]
Given the importance of developing new biopesticides and investigating their spectra of action, a recent survey showed promising results with the allelopathic plant Conyza canadensis (L.) Cronquist, which belongs to the Asteraceae family and is popularly known as horseweed.[7]
C. canadensis specimens collected in Brazil were extracted using dichloromethane, chloroform, and hexane, as described by Queiroz et al.,[7] in order to determine whether the compounds isolated from North American specimens were present in specimens growing in Brazil
Summary
Postharvest diseases are the main factors responsible for fruit losses along the production chain.[1,2] These diseases are usually caused by fungal pathogens that are commonly controlled by the application of synthetic fungicides.[3]. Given the importance of developing new biopesticides and investigating their spectra of action, a recent survey showed promising results with the allelopathic plant Conyza canadensis (L.) Cronquist, which belongs to the Asteraceae family and is popularly known as horseweed.[7] This plant is a potential source of bioactive compounds[8] and several studies have reported the fungitoxic effects of its essential oils,[9,10,11] the compounds responsible for such activity were not identified. Queiroz et al.[7] found three fungitoxic compounds in
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