natural-products-in-plant-pest-management

230 R.N. Kharwar and G. Strobelonly a few products from endophytic microbes for which total synthesis hasbeen successfully accomplished.Phomopsichalasin, a metabolite from an endophytic Phomopsis sp., representsthe first cytochalasin-type compound with a three-ring system replacingthe cytochalasin macrolide ring. This metabolite exhibits antibacterialactivity in disc diffusion assays (at a concentration of 4 μg/disc) against Bacillussubtilis, Salmonella gallinarum and Staphylococcus aureus. It also displays amoderate activity against the yeast Candida tropicalis (Horn et al., 1995).An endophytic Fusarium sp. isolated from Selaginella pallescens collectedin the Guanacaste Conservation Area of Costa Rica was screened for antifungalactivity. A new pentaketide antifungal agent, CR377, was isolatedfrom the culture broth of the fungus and showed potent activity againstC. albicans in agar diffusion assays (Brady and Clardy, 2000). Colletotricacid, a metabolite of Colletotrichum gloeosporioides, an endophytic fungus isolatedfrom Artemisia mongolica, displays antibacterial activity against bacteriaas well as against the fungus Helminthsporium sativum. Antimicrobialproducts have been identified from another Colletotrichum sp. isolated fromArtemisia annua, a traditional Chinese herb that is well recognized for itssynthesis of artemi sinin (an antimalarial drug) and its ability to inhabitmany geographically different areas. Not only did the Colletotrichum sp.found in A. annua produce metabolites with activity against human pathogenicfungi and bacteria, but also metabolites that were fungistatic to plantpathogenic fungi (Lu et al., 2000).A novel antibacterial agent, guignardic acid, was isolated from the endophyticfungus Guignardia sp.; the organism was obtained from the medicinalplant Spondias mombin of the tropical plant family Anacardiaceae found inBrazil. The compound was isolated by UV-guided fractionation of the fermentationproducts of this fungus and is the first member of a novel class ofnatural compounds containing a dioxolanone moiety formed by the fusionof 2-oxo-3-phenylpropanoic acid and 3-methyl-2-oxobutanoic acid, whichare products of the oxidative deamination of phenylalanine and valine,respectively (Fig. 11.6; Rodriguez-Heerklotz et al., 2001).Another antibacterial compound javanicin is produced by endophyticfungus Chloridium sp., under liquid- and solid-media culture conditionsOOOH 3 CO –CH 3OFig. 11.6. Guignardic acid from Guignardia sp. obtained from Spondias mombin, anAnacardiaceaeous plant in Brazil.