A B S T R A C TThe epicuticular waxes have significant economic and ecological importance. Based on this, the objective of this study was to evaluate the influence of the chemical composition of waxes in gall formation intensity in Croton spp. of the semi-arid region using a multivariate analysis. Intact leaves were used, and mature seven Croton species (Croton adamantinus, C. argyrophyllus, C. blanchetianus, C. glandulosus, C. grewioides, C. heliotropiifolius, C. urticifolius) were subjected to two successive extractions with dichloromethane and, then the chromatographic analysis (TLC and GC). The Principal Component Analysis (PCA) showed that there is a grouping of the species with high intensity of galls (C. adamantinus, C. argyrophyllus, and C. blanchetianus) according to the chemical similarity of the waxes and shown to be more defined by the fatty acids. However, C. urticifolius presents inserted in this group but does not contain galls. The n-alkanes C25 and C27 were instrumental in the absence of galls on C. glandulosus. Alcohols were responsible for explaining the low-intensity galls on C. grewioides while the alkanes C22, C32 and C33 and fatty acids C16:0 and C18: 0 were responsible for explaining the low-intensity galls on C. heliotropiifolius. Therefore, it was found that the presence of fatty acids and n-alkanes of long chains were prevalent in the chemical profile of the waxes of these species, thus indicating that the fatty acids likely components associated with the susceptibility of plants to galling. Keywords: Principal Component Analysis, caatinga, chromatography, cuticular lipid, galls. R E S U M OAs ceras epicuticulares têm grande importância econômica e ecológica. Com base nisso, o objetivo deste estudo foi avaliar a relação da composição química das ceras na intensidade de formação de galhas em Croton spp. de região semiárida por meio de uma análise multivariada. Foram utilizadas folhas íntegras e maduras de sete espécies de Croton (Croton adamantinus, C. argyrophyllus, C. blanchetianus, C. glandulosus, C. grewioides, C. heliotropiifolius, C. urticifolius) que foram submetidas a duas extrações sucessivas com diclorometano e, em seguida, às análises cromatográficas (CCD preparativa e CG). As Análises dos Componentes Principais (PCA) mostraram que há um agrupamento das espécies que apresentam alta intensidade de galhas (C. adamantinus, C. argyrophyllus e C. blanchetianus) em função da semelhança química das ceras epicuticulares, mostrando serem mais definidos pelos n-alcanos e ácidos graxos. Contudo, C. urticifolius apresenta-se inserido neste grupo embora não contenha galhas. Os n-alcanos C25 e o C27 foram determinantes na ausência de galhas em C. glandulosus. Os alcoóis foram responsáveis por explicar a baixa intensidade de galhas em C. grewioides, enquanto

The present study evaluated the chemical composition of the leaf essential oil of Myrcia loranthifolia from Atlantic Forest and Dry Forest of Brazil. The oil showed a mean yield of 0.23–0.33%. From 26 to 32 compounds were identified by GC–MS depending on the geographical origin of the plant. (E)–Caryophyllene (47.80%) and germacrene D (10.07%) predominated in the oil of samples from the Atlantic Forest. In Dry Forest, the main constituent identified in the oil was also (E)–caryophyllene, but it was detected in a lower concentration (15.59%). Cis–calamenene (11.40%), the second major constituent found in the oil of plants from Dry Forest, was not identified in samples from the Atlantic Forest. The qualitative and quantitative differences found may be due to local abiotic factors or inherent to genetic characteristics of the plants. The essential oil of M. loranthifolia constitutes one of the largest sources of (E)–caryophyllene yet unexplored.