title: Bioassay-directed isolation and identification of phytotoxic and fungitoxic acetylenes from Conyza canadensis.
abstract: Conyza canadensis (L.) Cronquist syn. (horseweed) is a problematic and invasive weed with reported allelopathic properties. To identify the phytotoxic constituents of the aerial parts, a systematic bioactivity-guided fractionation of the dichloromethane extract was performed. Three active enyne derivatives, (2Z,8Z)-matricaria acid methyl ester, (4Z,8Z)-matricaria lactone, and (4Z)-lachnophyllum lactone, were identified. The lactones inhibited growth of the monocot Agrostis stolonifera (bentgrass) and the dicot Lactuca sativa (lettuce) at 1 mg mL(-1), while the (2Z,8Z)-matricaria acid methyl ester was less active. In a dose-response screening of the lactones for growth inhibitory activity against Lemna paucicostata , (4Z)-lachnophyllum lactone was the most active with an IC50 of 104 μM, while the (4Z,8Z)-matricaria lactone was less active (IC50 of 220 μM). In a fungal direct bioautography assay, the two lactones at 10 and 100 μg/spot inhibited growth of the plant pathogenic fungi Colletotrichum acutatum , Colletotrichum fragariae , and Colletotrichum gloeosporioides . In a dose-response screening of the lactones against six different plant pathogenic fungi, (4Z,8Z)-matricaria lactone was more active than the commercial fungicide azoxystrobin on Col. acutatum , Col. fragariae , and Col. gloeosporioides at 30 μM and about as active as the commercial fungicide captan against Col. gloeosporioides , while (4Z)-lachnophyllum lactone was less active.
authors.affiliation: EMBRAPA Environment , C.P. 69, Jaguariúna, SP, 13820-000, Brazil.
authors.forename: Sonia C N
authors.initials: SC
authors.lastname: Queiroz
authors.forename: Charles L
authors.initials: CL
authors.lastname: Cantrell
authors.forename: Stephen O
authors.initials: SO
authors.lastname: Duke
authors.forename: David E
authors.initials: DE
authors.lastname: Wedge
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Nandula
authors.forename: Rita M
authors.initials: RM
authors.lastname: Moraes
authors.forename: Antonio L
authors.initials: AL
authors.lastname: Cerdeira
mesh_terms: D031703:Agrostis / Q000187:drug effects / Q000254:growth & development; D000480:Alkynes / Q000032:analysis* / Q000302:isolation & purification / Q000494:pharmacology; D000935:Antifungal Agents / Q000032:analysis* / Q000494:pharmacology; D029064:Araceae / Q000187:drug effects / Q000254:growth & development; D061046:Biological Control Agents; D005591:Chemical Fractionation; D020231:Colletotrichum / Q000187:drug effects / Q000254:growth & development; D035401:Conyza / Q000737:chemistry*; D007783:Lactones / Q000032:analysis; D018545:Lactuca / Q000187:drug effects / Q000254:growth & development; D010936:Plant Extracts / Q000032:analysis / Q000494:pharmacology; D053279:Polyynes / Q000032:analysis
chemical_list: C542189:(2Z,8Z)-matricaria acid methyl ester; D000480:Alkynes; D000935:Antifungal Agents; D061046:Biological Control Agents; D007783:Lactones; D010936:Plant Extracts; D053279:Polyynes