Marmeleiros are popularly known for the medicinal properties ascribed to their essential oils. This research aimed to analyze the essential oil of leaves from three Croton species (Croton argyrophylloides, Croton jacobinensis, and Croton sincorensis), to verify whether the daily time and harvest season in the year may interfere with their essential oils performance and composition. From each species, 1,500g of green leaves were harvested in Viçosa do Ceará - CE, at 6am and 12pm, during both dry and rainy seasons. Essential oil extraction was conducted by the method of water vapor drag and chemical profile was analyzed by gas chromatography-mass spectrometry (GC/MS). The highest yield was obtained at 12pm in the dry season for C. argyrophylloides and C. jacobinensis, and at 6am in the rainy season for C. sincorensis. Bicyclogermacrene demonstrated higher relative abundance in C. argyrophylloides (28.09 to 30.59%), C. jacobinensis (25.2 to 30.14%), and C. sincorensis (23.86 and 21.71%), and the only exception was at 6am in C. sincorensis, where (E)-caryophyllene was the most abundant compound (25.34%). The yield and composition of the studied species were influenced by rainfall, temperature, and sunlight, presenting statistical significant differences between the different periods studied. The species produce constituents with specific biological properties; and therefore, they can be used as a natural source.

RESUMO -O presente estudo objetivou avaliar a fi totoxidez e o potencial alelopático dos hidrolatos de Croton argyrophylloides Muell. Arg., C. blanchetianus Baill., C. jacobinensis Baill., C. nepetaefolius Kunth., C. sincorensis Mart. ex Muell. Arg. e C. zehntneri Pax. et. Hoff m. na germinação de diásporos de alface e tomate. Realizaram-se observações diárias e medição do teste-padrão de germinação (TPG), da primeira contagem (1ª C) e índice de velocidade de germinação (IVG). A intensidade da atividade fi totoxica de cada espécie, variou em função da concentração, da espécie receptora e do fotoperíodo. C. argyrophylloides, C. blanchetianus e C. nepetaefolius apresentaram ação inibitória em todos os fotoperíodos. Foram observados alguns efeitos estimulantes para a C. sincorensis e C. argyrophylloides. No entanto, os resultados deste estudo fornecem indicações consistentes do potencial alelopático das espécies testadas. Palavras-chave: fi totoxidez, hidrolato, EuphorbiaceaeABSTRACT -Allelopathic potential of six species of the genus Croton L. in the germination of lettuce and tomato. This study aimed to evaluate the phytotoxicity and allelopathic potential of hydrolats of Croton argyrophylloides Muell. Arg., C. blanchetianus Baill., C. jacobinensis Baill., C. nepetaefolius Kunth., C. sincorensis Mart. ex Muell. Arg. and C. zehntneri Pax. et. Hoff m. in the germination of diaspores of lettuce and tomato. There were daily observations and measurement of the standard test of germination (TSG), fi rst count (1ª C) and germination speed index (GSI). The intensity of the phytotoxic activity of each species varied according to concentration, species and photoperiod. C. argyrophylloides, C. blanchetianus, and C. nepetaefolius were inhibited in all photoperiods. Some stimulating eff ects were observed for C. sincorensis and C. argyrophylloides. Nevertheless, the results of this study provide consistent indications of the allelopathic potential of tested species.