Chemical screening and antibacterial activity of essential oil and volatile fraction of Dictyopteris polypodioides

The genus Dictyopteris, comprising 35 species, is known by its characteristic marine fragrances which is mainly associated to aspecific chemical composition. Dictyopteris polypodioides (D. polypodioides), known as Dictyopteris membranacea (D. membrcrnacea), is distributed in several region of the world and characterized by a wide range of bioactive compounds. In the current research, the chemical composition and antibacterial activity of the volatile fraction (VF) and essential oil (EO) of D. polypodioides are reported in a comparative objective. The VF was prepared from the crude ether extract, whereas, the EO was made from the dried alga. The GC/MS analysis of the VF and the EO revealed the presence of 72 and 70 compounds accounting for 86.4% and 80.6% of the total composition respectively. The main constituents in both oils were 3-hexyl-4,5-dithiacycloheptanone and dictyopterene. The antibacterial activity of the VF and the EO were evaluated by liquid-broth dilution method, against six strains including Staphylococcus aureus, Agrobacterium tumefaciens, Salmonella typhimurium, Bacillus cereus, Micrococcus luteus and Escherichia coli. Kanamycin and chloramphenicol were used as antibiotics references. The EO has shown a high inhibitory effect against all the microorganisms tested as compared to the VF. Staphylococcus aureus and Agrobacterium avnefaciens were the most sensitive bacteria with respect to the EO, where the MIC was around 1519 mu g/mL This strong antibacterial activity of the EO is related to the presence of high content of sulfur compounds, known by their broad spectrum of biological activities.