Leaves and flower heads of P. brevipedunculata were submitted to four drying-air temperatures (room temperature, 40, 50 and 60 ºC). Room temperature (approximately 30 ºC) and higher temperature drying (50 and 60 ºC) had a deleterious effect on the essential oil content. The recommended drying-air temperature for the species is 40 ºC for it results in the same amount of essential oil observed in fresh cut plants. Overall, 13 components accounting for more than 92% of the total composition were identified. Citral was the major component, followed by α-pinene and limonene. The essential oil showed high toxicity against Artemia salina larvae.

Este trabalho foi realizado com o objetivo de caracterizar a natureza química dos compostos da humina extraída em solo de área degradada pela extração de argila, com vegetação espontânea de Brachiaria mutica (Forsk.) Stapf e revegetada com Acacia mangium Willd. Após extração e purificação, a humina foi submetida à transesterificação com metanol trifluorato de B (BF3-MeOH), obtendo-se as subfrações alifáticas e aromáticas. Essas subfrações foram submetidas à cromatografia gasosa (Shimadzu GC-17A) combinada com a espectrometria de massa (Shimadzu GC/MS-qp5050A). Na subfração alifática obtida da cobertura com A. mangium, os compostos identificados foram: hexadecanoato de metila, octadecanoato de metila, heptadecano e 2-hidroxidodecanoato de metila; já na área com B. mutica os compostos foram: 14-metilpentadecanoato de metila e nonadecanoato de metila. Na subfração aromática, os compostos identificados na cobertura com A. mangium foram os mesmos obtidos naquela com B. mutica, sendo eles: 14-metilpentadecanoato de metila, 1,2 benzenodioato de 2 etilexila e butila. A leguminosa arbórea A. mangium proporcionou mudanças na fração mais recalcitrante das substâncias húmicas (humina), extraída da cava de extração de argila, preservando maior diversidade de compostos alifáticos.

This study aimed at characterizing the chemical aspects of the humin compounds of a degraded clay extraction area covered with spontaneous vegetation of Brachiaria mutica (Forsk) Stapf or afforested with Acacia mangium Willd. After extraction and purification, humin was subjected to transesterification using BF3-MeOH (boron trifluorate methanol) to obtain the aliphatic and aromatic sub-fractions. These sub-fractions were analyzed by gas chromatography-mass spectrometry. The following compounds were identified in the aliphatic sub-fraction of the A. mangium site: methyl hexadecanoate, methyl octadecanoate, methyl 2-hydroxidodecanoate and heptadecano, on the other hand, in B. mutica site the compounds were: methyl 14-methylpentadecanoate and methyl nonadecanoate. In the aromatic sub-fractions the compounds identified in soil samples colleted in A. mangium site were the same as those identified in B. mutica: methyl 14-methylpentadecanoate, 2-ethylexila 1.2 benzenodioate and buthyl. The re-vegetation of degraded area with the leguminous tree A. mangium inmduced changes in the recalcitrant fraction of humic substances (humin), preserving the diversity of the aliphatic compounds.