Secretory structures and chemical composition of the essential oil from leaves of Myrsine leuconeura Mart. (Primulaceae)

Abstract

Myrsine leuconeura Mart. is used by ethnic groups in Brazil to treat infections of the urinary tract, but the chemical profile and morphological characteristics of this medicinal plant have not yet been reported. We have identified the secretory structures of the leaves of this species and determined the influence of geographic site and season of harvesting on the accumulation and chemical composition of the essential oil. A histochemical study was performed using optical and scanning electron microscopy, while essential oils were obtained by hydrodistillation of dried leaves and analyzed by gas chromatography/mass spectrometry. The leaf oils were composed mainly of sesquiterpenes (93.9–96.6%), bicyclogermacrene (12.2–14.7%), (E)-caryophyllene (10.6–14.4%), α-guaiene(7.7–10.1%), spathulenol (6.9–9.6%) and δ-cadinene (6.7–7.2%) being the major constituents. Although site and season of collection did not influence the qualitative composition of the leaf oil, the accumulation of (E)-caryophyllene varied as a function of air temperature and rainfall. The secretory structures in M. leuconeura leaves were identified as peltate-type glandular trichomes, secretory canals, oil cells and mucilage cells. Essential oils were stored in solitary cells and secretory canals, most especially in the latter, but not in the glandular trichomes. This is the first report on the accumulation of essential oils in leaf epidermal cells in the genus Myrsine.