ABSTRACT
Alternaria brown spot (ABS), caused by the fungus Alternaria alternata pathotype tangerine, is one of the main phytosanitary problems for mandarin growers. About 15 applications per year of harmful fungicides are required for controlling ABS disease in citrus orchards. As chalcones seem to be less toxic to humans and environment than the commercial fungicides in use, this study initially aimed at synthesizing 137 chalcones through aldolic condensations between benzaldehydes and acetophenones. The resulting chalcones were screened for activity against A. alternata through a fungal growth assay that was carried out in 96-cell polypropylene plates, using the same concentration to all studied substances. The four active chalcones underwent conidia germination and mycelial growth, which confirmed the antifungal activity of the compounds. These chalcones were then poured onto Murcott tangor fruit that had been inoculated with conidia of the fungus. All four chalcones reduced the ABS progress to values significantly smaller (P0.05) than that observed for the control. Statistical calculations showed that the best results were afforded by two compounds, bearing a 2,4,5-trimethoxyphenyl group at position 3 of prop-2-enal and a 3-nitro- or 3-hydroxyphenyl group at position 1 of the aldehyde. Such compounds reduced the incidence of the disease in Murcott tangor fruit to values that did not differ statistically from those obtained with a commercial fungicide.
A mancha marron de Alternaria (MMA), causada pelo fungo Alternaria alternata patótipo tangerina, é um dos maiores problemas fitossanitários dos produtores de tangerina. Aproximadamente 15 aplicações de fungicidas de elevada periculosidade, por ano, são necessárias para o controle de MMA em várias plantações de citros. Como as chalconas parecem menos tóxicas para os seres humanos e para o ambiente que os fungicidas comerciais atualmente em uso, este estudo teve como objetivo inicial sintetizar 137 chalconas através da condensação aldólica de benzaldeídos com acetofenonas. As atividades das chalconas resultantes contra A. alternata foram avaliadas através do emprego de teste de crescimento fúngico em placas de polipropileno com 96 cavidades, empregando a mesma concentração para todas as substâncias estudadas. As quatro chalconas mais ativas foram submetidas a testes de germinação de conídios e de crescimento micelial, que confirmaram as atividades antifúngicas dos compostos selecionados. Estes foram então, aplicados em frutos de tangor Murcote que tinham sido inoculados com conídios do fungo. Todas as quatro chalconas reduziram o progresso de MMA a valores significativamente inferiores (P0.05) ao observado para o controle. Cálculos estatísticos mostraram que os melhores resultados foram obtidos para dois compostos, que tinham um grupo 2,4,5-trimetoxifenil na posição 3 do prop-2-enal e um grupo 3-nitro- ou 3-hidroxifenil na posição 1 do aldeído. Tais compostos reduziram a incidência da doença em frutos de tangor Murcote a valores que não diferiam estatisticamente do obtido com um fungicida comercial.
Subject(s)
Citrus , Chalcones , Alternaria , Fungicides, IndustrialABSTRACT
The synthetic n-alkyl esters of gallic acid (GA), also known as gallates, especially propyl, octyl and dodecyl gallates, are widely employed as antioxidants by food and pharmaceutical industries. The inhibitory effects of GA and 15 gallates on Herpes Simplex Virus type 1 (HSV-1) and Human Immunodeficiency Virus (HIV-1) replication were investigated here. After a preliminary screening of these compounds, GA and pentyl gallate (PG) seemed to be the most active compounds against HSV-1 replication and their mode of action was characterized through a set of assays, which attempted to localize the step of the viral multiplication cycle where impairment occurred. The detected anti-HSV-1 activity was mediated by the inhibition of virus attachment to and penetration into cells, and by virucidal properties. Furthermore, an anti-HIV-1 activity was also found, to different degrees. In summary, our results suggest that both compounds could be regarded as promising candidates for the development of topical anti-HSV-1 agents, and further studies concerning the anti-HIV-1 activity of this group of molecules are merited.