Morphological and chemical composition of the essential oil of the leaf of Schistostephium heptalobium

Abstract

The morphology of Schistostephium heptalobium was investigated by using electron microscopical examination. The scanning electron microscope revealed that the leaves of this plant are characterized by short, multicellular glandular trichomes and long hairy-fibrous tubular non-glandular trichomes. These trichomes are associated with crystal-like deposits. The Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDX) showed that, Fe, Al, K, Mg and Si are the major components of the crystals-like deposits. The area of the non-glandular trichomes where these crystals-like substances are produced showed Al, Ca, K, Mg, Mo, Na, Pi and Si as major residue when analysed by SEM-EDX. However, the SEM-EDX analysis of glandular trichome sac and the content of the sac showed different results. The anatomical investigation also showed that the ends of the non-glandular trichomes are fibrous and have a tubular base while the glandular trichomes contain cuticular sac. The sac contains by products which are referred to as essential oil. These by-products are regarded as the first line of defence in this plant. Hydro-distillation of fresh leaves of S. heptalobium yielded 2.5% (v/v) of the essential oil. The GC-MS analysis of the oil revealed that the essential oil of S. heptalobium is characterized by α-pinene, sabinene, myrcene, α-phellendrene, 1.8-cineole, γ-terpinen, α-thujone, cis-sabinene hydrate, camphene, terpinen-4-ol, α-terpineol, 2-cyclohexen-1one, geranial, phenol, neryl acetate, β-caryophyllene, β-selinene and caryophyllene oxide. Key words: Glandular trichomes, non-glandular trichomes, SEM-EDX analysis, essential oil composition, Schistostephuim heptalobium.