Estudos químicos e anatômicos em espécies de Myrtaceae e Asteraceae e primeiros registros de coléteres em Myrtaceae / Chemical and anatomical studies in Myrtaceae and Asteraceae species and first report of colleters in Myrtaceae

Cleber José da Silva

This paper presents data on the chemical composition and antibacterial activity of volatile oils fron three Myrtaceae genera (Callistemon, Kunzea and Melaleuca) grown in Brazil, and one species of the Asteraceae family (Sphagneticola trilobata), ruderal and used in folk medicine. The volatile oils of Myrtaceae species were investigated for its chemical composition. They were characterized by a high content of monoterpenoids of which 1,8-cineole (88.0%, 65.0% and 77.0% for M. hypericifolia, C. viminalis and C. citrinus respectively), terpinen-4-ol (47.0% and 49.8% for M. thymifolia and C. polandii respectively) and α-pinene (54.5% for Kunzea ericoides) were the major components. The oil from M. linariifolia was characterized by a high concentration of methyleugenol (87.2%). The Myrtaceae’s volatile oils were investigated for its antibacterial activity against Gram-positive and Gram-negative bacteria using both disc diffusion and broth microdilution methods. The results showed disagreement among the diffusion and microdilution techniques. The antimicrobial activity essential oils tests of the can be hindered by the oil volatility, its water insolubility and its chemistry complexity. The microdilution method results showed a strong antibacterial activity of the essential oils tested. Anatomical and histolochemical investigations of the S. trilobata secretory structures in leaves and stems, and the seasonal variation, antibacterial and phytotoxicity activity of volatile oils were carried out. Histochemical techniques enabled specific location of the site of essential oil accumulation in the internal and external structures (canals and thricomes, respectively). Histochemical analysis showed that the secretory trichomes produced steroids. The S. trilobata essential oil exhibited significant suppression on germination and radical growth of seeds in Allium cepa and shows a great antimicrobial activity against Gram-positive and Gram-negative bacteria tested. The highest yield was obtained from plants collected in winter, when occured low temperature and precipitation. The essential oil was characterized by a high percentage of hydrocarbon sesquiterpenes, hydrocarbon monoterpenes and low levels of oxygenated sesquiterpenes. The major components were Germacrene D (11,9%-35,8%), α-felandrene (1,4%-28,5%), α-pinene (7,3%-23,8%), E-caryophyllene (4,6%-19,0%), bicyclogermacrene (6,0%-17,0%), limonene (1,8%-15,1%) and α-humulene (4,0%-11,6%). The percentage of most of the individual constituents present in S. trilobata volatile oil changed significantly during the months. This is the first report of occurrence of colleters in the Myrtaceae family. Species of the Leptospermoideae and Myrtoideae subfamily were studied from the standpoint of morphology, anatomy and histochemistry of colleters. The colleters of Myrtaceae not present the typical anatomical composition of a column of parenchyma cells surrounded by a secretory epidermis. A specific nomenclature is proposed based on this singularity and in the morphological description of Myrtaceae colleters, classifying them into three types: petaloid colleters, which occurs only in the Leptospermoideae subfamily; euriform colleters and conic colleters, which occur in the two subfamilies. The secretion analysis by electrophoresis method (SDS-PAGE) revealed the proteins absence in the Myrtaceae colleter’s secretion in two species analyzed.

Estudos químicos e anatômicos em espécies de Myrtaceae e Asteraceae e primeiros registros de coléteres em Myrtaceae / Chemical and anatomical studies in Myrtaceae and Asteraceae species and first report of colleters in Myrtaceae

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