Chemical and Biological Investigations of Essential Oils from Stem Barks of Enantia Chlorantha Oliv. and Polyalthia Suaveolens Engler. & Diels. from Cameroon

Abstract

The chemical composition and in vitro bioactivities of essential oils obtained by hydrodistillation of barks of Enantia chlorantha and Polyalthia suaveolens, two Annonaceae from Cameroon were investigated. Chemical analyses by GC and GC-MS showed that for both plants sesquiterpenes are predominant, the main constituents being 1,5-epoxysalvial-4(14)-ene (12.8%), caryophyllene oxide (13.4%), humulene epoxide II (8.1%) and spathulenol (7.0%), for E. chlorantha; β-caryophyllene (16.0%), germacrene D (8.5%), epi-α-cadinol (8.3%), caryophyllene oxide (7.3%), salvia-4(14)-en-1-one (7.3%) and 5-cadinene (6.0%) for P. suaveolens. Evaluation of the antiradical scavenging activity by the 1,1-diphenyl-2-picryhydrazyl (DPPH) method indicated that the P. suaveolens essential oil was more active (SC₅₀= 0.71 g/L) than that from E. chlorantha (8.0 g/L). In both cases, the essential oils were less efficient than BHT, taken as a reference (8.8 10-³g/L). In vitro microbiological screening revealed that E. chlorantha essential oil presents a significant activity against the three bacterial strains, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus (with a maximum activity > 90% at 2 mg/mL) and six fungal strains, Candida albicans, Microsporum canis, Trychophyton rubrum, Fusarium moniliforme, Aspergillus flavus and Aspergillus niger (with a maximum activity > 75% at 2 mg/mL). The volatile extract of P. suaveolens is globally less efficient, as it does not inhibit the growth of either S. aureus or A. flavus.