Botanical fungicides: natural and semi-synthetic ceveratrum alkaloids

✍ Scribed by Oros, Gyula; Ujváry, István

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 187 KB
• Volume: 55
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199903)55:3<253::aid-ps926>3.0.co;2-6

✦ Synopsis

The practical potential of the main bioactive principles of sabadilla, a botanical insecticide prepared from the seeds of Schoenocaulon officinale, and related semi-synthetic ceveratrum alkaloids in controlling phytopathogenic bacteria and fungi was explored. Evaluating 35 compounds belonging to this group of steroid alkaloids revealed antimicrobial eþ ects against Erwinia, Corynebacterium, Fusarium, Glomerella and Plasmopara species. Signiücant activities were displayed against the sunýower downy mildew fungus, Plasmopara halstedii. The ceveratrum alkaloids are thought to interact with the cell membrane, disrupting its integrity and/or altering its function. In contrast to commercial fungicides aþ ecting either the parasitising thallus or the asexual spores of P. halstedii, ie, only a single developmental stage, the alkaloids tested disrupt its life cycle at several points in hostdependent and host-independent stages. Among the natural alkaloids, cevacine and cevadine were the most eþ ective against sunýower downy mildew and the activity of the semi-synthetic oleoyl veracevine and cevagenine was comparable to that of metalaxyl. Sunýowers showed good tolerance to these highly active natural and semi-synthetic ceveratrum alkaloids. Our results indicate that the modest anti-oomycete activity of the natural sabadilla components can be greatly improved by appropriate structural modiücations and thus establish the ceveratrum alkaloids as potential antifungal agents with a novel mode of action.