Location: Natural Products Utilization ResearchTitle: Phytotoxic furanocoumarins from the shoots of Semenovia transiliensis Regel & Herder Author
Submitted to: Natural Product Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2012
Publication Date: 10/1/2012
Citation: Sondhia, S., Duke, S.O., Green III., S., Gemejiyeva, N.G., Mamonov, L.K., Cantrell, C.L. 2012. Phytotoxic furanocoumarins from the shoots of Semenovia transiliensis Regel & Herder. Natural Product Communications. 7(10):1327-1330. Interpretive Summary: Weeds are known to cause enormous losses due to their interference in agro-ecosystems. Because of environmental and human health concerns, worldwide efforts are being made to reduce the heavy reliance on synthetic herbicides that are used to control weeds. The decline in the number of new synthetic herbicides derived from traditional screening programs and the increasing evolution and spread of weed resistance to synthetic herbicides provides impetus for natural products as important alternatives for herbicide development. Some plant secondary metabolites possess a wide diversity of bioactivity, including phytotoxicity. These phytochemicals might be used directly or as a template for new synthetic pesticides. We have screened a number of crude extracts from plants native to the Republic of Kazakhstan against A. stolonifera and L. sativa. Based on such preliminary screening of crude extracts for phytotoxicity, the methanolic/dichloromethane extract of S. transiliensis was selected for further investigation. In this paper we systematically examine S. transiliensis for phytotoxic activity. Our results show that S. transiliensis is rich in furanocoumarins, which are probably involved in various aspects of the chemical ecology of the species. Bergaptin and xanthotoxin were the most active of the compounds, with moderate activity. Unfortunately, the general cytotoxicity of furanocoumarins makes them an unlikely candidate for pesticide discovery.
Technical Abstract: Discovery of novel, natural herbicides has become important to manage increasing weed resistance to synthetic herbicides and environmental issues. The systematic bioassay-guided fractionation and purification of the methylene chloride/methanol extract of the shoots of Semenovia transiliensis led to the isolation of several phytotoxic compounds. Lactuca sativa L. (lettuce, a dicot) and Agrostis stolonifera L. (bentgrass, a monocot) bioassays were used to identify and isolate the phytotoxic fractions. A number of furanocoumarins compounds isolated from S. transiliensis shoots were phytotoxic to both test species. These included psoralen, isopsoralen, heratomin, isopentenyloxyisobergapten, imperatorin, bergapten, xanthotoxin, heraclenin, and heraclenol. All the active secondary metabolites isolated from the shoots of S. transiliensis were furanocoumarins. Identification of the furanocoumarins was accomplished using mass spectrometry and one- and two-dimensional NMR techniques. Phytotoxic activity of isolated compounds was evaluated in a dose–response manner from 0.3 to 1000 µM. In general, all of the compounds were more active on A. stolonifera than L. sativa. Bergaptin and xanthotoxin were the most active of the compounds, with moderate activity at 100 µM. Imperatorin and xanthotoxin inhibited growth of Lemna paucicostata Hegelm. 50% at 29 and 60 µM, respectively. Our results show that S. transiliensis is rich in furanocoumarins, which are probably involved in various aspects of the chemical ecology of the species. Unfortunately, the general cytotoxicity of furanocoumarins makes them an unlikely candidate for pesticide discovery.