Comparative Pharmacognostic and Chemical analyses of Eucalyptus camaldulensis Dehnh and Eucalyptus citriodora (Hook)

J.A. Ibrahim, B. Mustapha, J.I. Ogah, H.O. Egharevba

Abstract


Eucalyptus camaldulensis and E. citriodora are two Eucalyptus species that are very rich in essential oil and are often used in ethnomedicine for the treatment of different ailments. However, the leaves of E. camaldulensis and E. citriodora are very similar in structure and can be very difficult to distinguish when dry or in fragments. Hence, comparative phytochemical screening, elemental, pharmacognostic and GCMS analyses were carried out on the leaves and leaves extracts of two Eucalyptus species harvested from a garden in order to establish some distinguishing physicochemical and pharmacognostic characteristics. The leaf essential oils of the two species were extracted by hydro-distillation and analyzed on GC-MS. The results of phytochemical screening revealed presence of saponins, carbohydrates and sterols in both species. Elemental analysis indicated that the levels of the elements in the two samples differ. Chromium (Cr) was below detectable limit in the two samples while Pb, Mn, Zn, Fe, Cu and Mg were detected and quantified. Only Eucalyptus citriodora showed the presence of flavonoids.  Tannins, alkaloids and anthraquinones were not detected in the two Eucalyptus species. The dry-leaf moisture contents were 9.5% and 9.7% for camaldulensis and citriodora, respectively. The GC-MS analyses of the hydro-distilled essential oils from both plants showed 57 and 39 components for camaldulensis and citriodora, respectively. 35 and 18 components were identified respectively from the two species. However, only seven (7) components were common to the two species, which include 4-terpineol (16.30% and 19.32%), Spathulenol (15.01% and 4.65%), Thymol (4.50% and 1.66%), α-terpineol (1.59% and 3.98%), caryophyllene (0.10% and 3.93%), viridiflorol (0.20% and 2.06%) and phytol (0.30% and 2.21%), respectively. Citronellol and its acetate and isopulegol and its acetate were absent in E. camaldulensis and were appreciably present in E. citriodora. α-Eudesmol was appreciably present in E. camaldulensis but absent in E. citriodora. Citronellol, isopulegol and α-eudesmol may be the distinctive marker compounds between the two species. The microscopic characters of the leaves revealed useful diagnostic parameters for the species. The information obtained from this study, is important not just for establishing morphological or phytoconstituents differences necessary for identification and authentication purposes, but also for monograph development, standardization and pharmaceutical reference as possible source of lead/ hit compounds in drug development or as raw material in drug excipients. 

Keywords: Eucalyptus camaldulensis; Eucalyptus citriodora; Essential oil; GC-MS; Pharmacognostic 


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Chemical Society of Nigeria