Bioactivity of Sesquiterpene Constituents from Magnolia Grandiflora and Varthemia Iphionoides against Certain Food Borne Bacteria and Phytopathogenic Fungi

• Samir A. M. Abdelgaleil,(1), Maher M. Al-Dabbas(2), Soad M. Ahmed(1) And Fumio Hashinaga(2)
• (1)Pesticide Chemistry Department, Faculty of Agriculture (Elshatby), Alexandria University, Alexandria, Egypt
• (2)Department of Biochemistry and applied Biosciences, Faculty of Agriculture, Kagoshima University, 1-21-24 korimoto, Kagoshima 890-0065, Japan
• The Third International Conference onIPM Role in Integrated Crop management and Impacts on Environment and Agricultural Products. 26-29 November 2005, Giza, Egypt.

Abstract

Investigation of Magnolia grandiflora L. and Varthemia iphionoides (Boiss and Bl.) extracts resulted in the isolation of three sesquiterpenes. Chromatographic separation of the stem bark dichloromethane extract of M. grandiflora on silica gel open column followed by recrystallization yielded two sesquiterpene lactones; costunolide and parthenolide. The bioassay-guided fractionation of ethyl acetate extract of the whole aerial parts of V. iphionoides and further purification of the most antibacterial active fraction led to isolate an eudesmanolide sesquiterpene, selina-4, 11(13)-dien-3-on-12-oic acid. The structure of these three compounds and a parthenolide derivative, 1,10-epoxyparthenolide, was determined by spectroscopic methods. The isolated sesquiterpenes were examined in vitro for their antibacterial activities against six bacterial species (Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Escherichia coli, Bacillus cereus and Salmonella enteritides). Parthenolide and costunolide showed the highest antibacterial activity against all tested bacteria followed by 1,10-epoxyparthenolide, while selina-4, 11(13)-dien-3-on-12-oic acid showed the lowest activity. Parthenolide was the most potent against S. aureus, B. cereus and S. enteritidis with minimum inhibitory concentration (MIC) of 25 mg/l. On the other hand, the antifungal activity of the three sesquiterpene lactones was assessed using radial growth inhibition technique against six phytopathogenic fungi (Alternaria alternata, Helminthosporium spp., Nigrospora spp., Fusarium oxysporum, Fusarium culmorium and Rhizoctonia solani). Costunoilde displayed the strongest antifungal activity among the tested compounds against three fungi, Nigrospora spp., R. solani and Helminthosporium spp., with EC50 values of 0.48, 2.92 and 2.96 mg/l, respectively, while parthenolide exhibited the highest antifungal activity against A. alternata and F. culmorium (EC50 = 4.07 and 50.27 mg/l, respectively). This is the first report on the antibacterial and antifungal activities of these sesquiterpenes.