István Ujváry

Comparative topical pheromonotropic activity of insect pyrokinin/PBAN amphiphilic analogs incorporating different fatty and/or cholic acid components☆

This study presents a comparison of the topical pheromonotropic activity in the tobacco budworm moth of a series of amphiphilic pseudopeptide analogs of the insect pyrokinin/PBAN peptide class incorporating fatty acids of varying chain lengths. While the C16 analog fails to penetrate the moth cuticle, and the C12 only moderately so, shorter chain analogs transmigrate the moth cuticle readily with decreasing cuticle-retention properties. A cholic acid analog topically induces twice the maximal pheromone titer of injected native hormone. From a pest management perspective, these non-aromatic hydrophobic components are expected to be more environmentally benign than benzenoid components previously used in topical insect peptide analogs.

Transforming natural products into natural pesticides-experience and expectations

Dr. Istv~in Ujv~y, born 1953. Senior research scientist, Chemical Research Center, Hungarian Academy of Sciences (HAS), Budapest, Hungary. Dipl. Chemical Engineering (1977), Ph.D. in Organic Chemistry (1995) (both at the Technical U. of Budapest). 1977-82, research scientist, EGIS Pharmaceuticals, Budapest; 1982-99, senior research scientist, Plant Protection Inst., HAS; 2000-, senior research scientist, Chemical Research Center, HAS. Visiting scientist: 1984, Dept. of Zoology, U. of Washington, Seattle, WA; 1987-89, Dept. of Chemistry, U. of New York at Stony Brook, Stony Brook, NY; 1989-90, Dept. of Environmental Sciences, Policy and Management, U. of California, Berkeley, CA; 1996-97, USDAARS, College Station, TX, all USA. Research grants: from the HAS, Hungarian Scientific Research Fund, National Office of Technology and Development, American-Hungarian Joint Research Fund, European Union, IAEA. Past and current interests: chemistry and toxicology of synthetic and natural pest control agents; synthesis of radiolabeled insect hormones for receptor studies; insect pheromones and attractants; carboranecontaining compounds; environmental contaminants; BIOSTER database for drug design; drugs of abuse. Editorial board member of Pest Management Science. Awards: HAS Award for Young Investigators (1987). Author and co-author of over 70 research publications; inventor or co-inventor of 21 patents.

Identification of Sex Pheromone Composition of Click Beetle Agriotes brevis Candeze

Geranyl butyrate (GB) and (E,E)-farnesyl butyrate (FB) were identified in the pheromone gland extract of females of the click beetle, Agriotes brevis (Candeze) (Coleoptera: Elateridae) as the major sex pheromone components. Polyethylene vial dispensers containing 20–200 mg of a 1:1 mixture caught high numbers of beetles. Captures did not decrease even after 73 days of field exposure of dispensers. At sites where both Agriotes sputator L. and A. brevis were present, the above baits were selectively catching only A. brevis, despite the fact that GB is also the main pheromone component of A. sputator, suggesting that FB has a role in reproductive isolation. In the early part of the season, traps into which the insects could both crawl and fly captured more A. brevis than designs where the insects could only fly in. Trap design was not important later in the season. This indicates the need for future development of a trap suitable for use throughout the whole season.

Semi-natural products and related substances as alleged botanical pesticides †

Plants are a virtually inexhaustible source of structurally diverse biologically active substances. In some cases, however, xenobiotics or their biotransformed derivatives can also be found in extracts from botanical sources. Whilst it is not improbable that plants are able to biosynthesise such compounds, the fact that they have similar, or even identical, structures to those of synthetic materials used in practice indicates a problem in determining their origin and blurs the borderline between natural and man-made substances. The recent identification of a herbicide-like 1,3,5-triazine (halimedin) from an algal source illustrates the difficulty of separating a natural from a semi-natural product, the latter being defined as substance of apparently man-made origin that is re-isolated from natural sources. Additional literature reports shown here demonstrate that pesticide contamination can turn up in unexpected locations. Although these cases appear to be only curiosities, they have the potential of toxicological or ecological risks.

Simple and economic syntheses of some (Z)-7- and (Z)-9-alkenyl acetates, and of (E,Z)-7,9-dodecadien-1-yl acetate, the sex pheromone of the European grapevine moth, using aleuritic acid as a common starting material.

Short syntheses of (Z)-7-dodecen-1-yl acetate, (Z)-7-tetradecen-1-yl acetate, (Z)-9-dodecen-1-yl acetate, and (Z)-9-tetradecen-1-yl acetate from 7-hydroxyheptanal and 9-oxononanoic acid precursors obtained by oxidative cleavage of easily available aleuritic acid are reported. The key step in these syntheses is a stereoselective Wittig reaction between aldehyde and alkyl-phosphonium salt. Wittig-Horner type reaction of 7-hydroxyheptanal and diethyl cyanomethylphosphonate gave the α,β-unsaturated nitrile derivative which after protection of the hydroxyl group was reduced to the corresponding aldehyde. Wittig reaction of the latter, followed by acetylation, completed the synthesis of (E,Z)-7,9-dodecadien-1-yl acetate, the sex pheromone of the European grapevine mothLobesia botrana Schiff.

Geranyl hexanoate attracting male click beetles Agriotes rufipalpis Brullé and Agriotes sordidus Illiger (Col., Elateridae)

Abstract:  In field screening tests in Hungary, traps baited with geranyl hexanoate captured males of the click beetle Agriotes rufipalpis Brullé, whereas in Italy males of Agriotes sordidus Illiger (Col., Elateridae) were captured. Geranyl hexanoate‐baited traps could be very useful in rationalizing the control of these pests. Such traps can give useful information without making expensive and time‐consuming samplings of the soil layers in search of larvae. Traps can be effective also in describing swarming patterns and identifying the peak of male activity, thus yielding an estimate of the level of adult populations, making it possible to forecast future outbreaks and to concentrate agronomic and chemical control strategies against the pests most effectively.

Botanical fungicides: natural and semi-synthetic ceveratrum alkaloids

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 effects against Erwinia, Corynebacterium, Fusarium, Glomerella and Plasmopara species. Significant activities were displayed against the sunflower 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 affecting 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 host-dependent and host-independent stages. Among the natural alkaloids, cevacine and cevadine were the most effective against sunflower downy mildew and the activity of the semi-synthetic oleoyl veracevine and cevagenine was comparable to that of metalaxyl. Sunflowers 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 modifications and thus establish the ceveratrum alkaloids as potential antifungal agents with a novel mode of action.

Partial synthesis of 3-O-vanilloylveracevine, an insecticidal alkaloid from Schoenocaulon officinale.

3-O-Vanilloylveracevine has been synthesized for the first time in 70% overall yield by conversion of veracevine into its 3-O-(4-benzyloxy-3-methoxybenzoate) followed by catalytic hydrogenation. The insecticidal activity of the semisynthetic substance against three pest species is inferior to that of cevadine and veratridine, the major components of the insecticidal sabadilla alkaloid mixture.

An aggregation attractant for the sugar-beet weevil, Bothynoderes punctiventris

During our screening studies, attractiveness of a ternary mixture of synthetic Grandlure I [racemic cis‐1‐methyl‐2‐(1‐methylenethenyl)‐cyclobutane ethanol], Grandlure II [(Z)‐2‐(3,3‐dimethyl)cyclohexylidene ethanol], and Grandlure III–IV [(Z)‐ and (E)‐2‐ochtodenal; (Z)‐ and (E)‐(3,3‐dimethyl)cyclohexylidene acetaldehyde] for the sugar‐beet weevil, Bothynoderes punctiventris Germar (Coleoptera: Curculionidae), was observed in field‐trapping tests at several sites in Hungary and Serbia. The mixture attracted both males and females. Later tests revealed that of the components in the ternary mixture, only Grandlure III–IV were responsible for attraction, and the addition of Grandlures I or II in varying percentages had no influence on trap captures. Traps baited with 50–50 000 µg of Grandlure III–IV on rubber or polyethylene dispensers yielded high catches of weevils. When testing synthetic samples enriched in the respective geometrical isomer, Grandlure IV had a tendency of catching more weevils, but differences were not significant from lower catches by a 1:1 Z:E blend or Grandlure III. In gas chromatography–flame ionization detection/electroantennographic detection studies, antennae of both female and male weevils were more responsive to the (E)‐ than to the (Z)‐isomer suggesting a more important role for Grandlure IV. Efforts to verify the presence of Grandlure III or IV in volatiles collected from either sex of live sugar‐beet weevils or body washings with pentane remained inconclusive. Traps baited with Grandlure III–IV can now be used as sensitive and powerful trapping tools in the control of the sugar‐beet weevil.

Projuvenoids: Synthesis and biological evaluation of sulfenylated, sulfinylated, and sulfonylated carbamates

Applying the proinsecticide principle developed earlier for neurotoxic carbamate insecticides, a series of new N-sulfenylated, N-sulfinylated, and N-sulfonylated derivatives of fenoxycarb were synthesized and evaluated for juvenile hormone mimicking activity. Laboratory evaluations of the compounds using Pieris brassicae and Sitophilus oryzae, as well as field experiments using Bemisia tabaci, showed that several symmetrical biscarbamates with either a sulfenyl or sulfinyl bridge possessed higher activity than the parent carbamate. From the unsymmetrical compounds containing biologically inert derivatizing moieties, one of the sulfenylated biscarbamates also showed improved activity against P. brassicae. The changes in the biological activity of the sulfur-containing derivatives compared to that of the parent compound are attributed to the modified physicochemical characteristics, i.e., increased lipophilicity facilitating penetration, transport, as well as protection of the compound from metabolism.