Bioactive essential oils from the Cameroonian rain forest: A review - Part II

Eighty-nine essential oil analyses carried out on Cameroonian plant material by gas chromatography are reviewed, and structures of sixty one main oil compounds are presented. Plant samples had been collected all over the rainforest area and further northwards, covering forty plant species belonging to ten families. For these plants, common names, traditional use as well as bioactivity and toxicity of their essential oils in vitro and in vivo are compiled. Data show that oils from leaves, bark, roots, fruit, rhizome or seeds display their own one to four main essential oil components. Each of them contributing more than 10% to over 90% of the oil´s volume, which sums up to species-unique essential oil fingerprints and decreasing similarity of these fingerprints with increasing phylogenetic distance between species. This review article shows that the environmental factor include, temperature, rainfall (Littoral region), humidity (Center, South, East and West regions) and solar radiation (Adamaoua, North and Far-north regions) as well as the soil nutrients influence the secondary metabolite composition of the plants. Bioassays valorized traditional use of a good number of oils, for example against the dermatophytic fungus Trichophyton rubrum being twice as effective as amphothericin B®; against the chloroquine resistant Plasmodium falciparum; against cancer cell lines; and against a variety of human pathogen bacteria, being up to ten times as effective as ciproxin®, lidaprim®, tetracycline hydrochloride® and lidaprim®. Importantly, in an experiment employing the stored product beetle Callosobruchus maculatus, the leaf oil of Lippia adoensis (Verbenaceae) indicated neurotoxicity, so that preparations should be applied with care. Follow up work may focus on bioassays with commercial pure compounds, with the goal to improve effectivity and doses calculation for traditional essential oil medicines and agricultural products.