Ethno-botanical survey, Chemical Composition and in vitro Antimicrobial activity of Essential oil from the root bark of hazomalania voyronii (jum.) Capuron (hernandiaceae)

  Microbial infectious diseases constitute a major public health problem worldwide. The emergence of multidrug resistance among several pathogenic organisms to drugs commonly used to treat such diseases is a great challenge today. The renewed interest that is given to indigenous medicinal plants as alternative sources of antimicrobials is due to the enormous chemical and structural diversity of plant derived secondary metabolites. Hazomalania voyronii is widely used in Malagasy Traditional Medicine as an herbal remedy to treat incurable wounds and bacterial infections.  The Aim of the study was to evaluate the chemical composition and antimicrobial activity of essential oil from the root bark of H. voyronii. An ethno-botanical survey was conducted in the south of Madagascar from Novembre to December 2011 according to the principles laid out in the Declaration of Helsinki and the Nagoya protocol. Twenty five traditional healers were interviewed about medicinal plants used in folk medicine to treat wounds and bacterial infections. The most cited plant H. voyronii in this category (use value= 0.59; Informant consensus factor= 0.35) was collected and identified at the Department of Botany, Tsimbazaza Zoological and Botanical Park, Antananarivo, Madagascar. Essential oil was isolated from the root bark of this plant species by hydro-distillation. Antimicrobial activities were carried out using agar disc diffusion and micro-dilution broth methods with Gram-positive and Gram-negative bacteria as models. The chemical compositions of the essential oils were determined by Gas chromatography-Flame Ionization Detector (GC-FID) and Gas chromatography-Mass spectrometry (GC/MS). Analysis of the root barks essential oil of H. voyronii (Jum.) Capuron by GC-FID and GC/MS enabled the identification of 28 compounds corresponding to 92.2% of the total essential oil composition. Based on functional groups classification, the essential oil from the root bark of the H. voyronii contained 13.4% of monoterpens hydrocarbons, 0.08% of sesquiterpens hydrocarbons, 36.6% of oxygenated monoterpens and 42.2% of oxygenated sesquiterpens. The major compounds were (-) Spathunelol (42.3%), Eucalyptol (22.0%), Limonene (10.3%), Borneol (10.2%), Myrtenal (2.0%), Perrylaldehyde (1.3%) and α-pinene (1.4%). The essential oil from the root bark of H. voyronii originated from Madagascar showed bactericidal activity (MBC/MIC ≤ 4). The ability of essential oils in this study to display antimicrobial activity may represent a rational explanation for the use of this plant species for wounds healing and treatment of bacterial infections by Malagasy traditional healers. Further studies involving the evaluation of both cytotoxicity of this oil toward human cells and the role of the lead molecules in the antimicrobial activity of the essential oil and combinational studies with conventional drugs are in progress.