Maryla Szczepanik

Feeding deterrent activity of terpenoid lactones with the p-menthane system against the Colorado potato beetle (Coleoptera: Chrysomelidae).

Abstract Feeding deterrent activity of some enantiomeric pairs of terpenoid lactones with the p-menthane system was tested against larval and adult Colorado potato beetle (Leptinotarsa decemlineata Say). The lactones were synthesized from optically pure isomers of pulegone and isopulegol. Monoterpene ketones and alcohols with the p-menthane system were weak antifeedants toward both Colorado potato beetle developmental stages. The introduction of the lactone moiety and an accessory functional group (hydroxy or ketone group) into the p-menthane skeleton increased feeding deterrent activity of the compounds. Our results show a correlation between chemical structure and antifeedant activity and indicated that the sensitivity of Colorado potato beetle to the tested lactones depends on the chiral centers configuration and the developmental stage of insects tested.

Terpenoid lactones with the p-menthane system as feeding deterrents to the lesser mealworm, Alphitobius diaperinus

The application of antifeedants, often in combination with other methods within integrated pest management (IPM) strategies, has proven to be a good way to control insect pests. Little is known about compounds that have antifeedant activity against the lesser mealworm, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae). The antifeedant properties of optically pure isomers of pulegone and isopulegol and some enantiomeric pairs of bicyclic terpenoid lactones with the p‐menthane system, derived from these isomeric starting compounds, were studied in choice and no‐choice tests with the lesser mealworm. The original monoterpenes and γ‐spirolactones were weak feeding deterrents to larvae and adults of A. diaperinus. The δ‐hydroxy‐γ‐spirolactones showed significant activity against adults, but substituting the hydroxy group with a ketone group considerably reduced the deterrent activity of the resulting δ‐keto‐γ‐spirolactones. The bicyclic γ‐hydroxy‐δ‐lactones with condensed rings and with the (1S,6R,8R)‐(+) and (1R,6S,8S)‐(–) configuration of the chiral centres, and δ‐hydroxy‐γ‐lactone (1S,4S,6S)‐(+) were very strong antifeedants to both larvae and adults. The hydroxy groups and the configuration of the chiral centres of the molecules were very important features for determining the antifeedant activity of the lactones tested. Generally, the compounds studied were better antifeedants to adults than to larvae.

Structure-related antifeedant activity of halolactones with a p-menthane system against the lesser mealworm, Alphitobius diaperinus Panzer.

BACKGROUND Feeding deterrent activity of synthetic halogen lactones against larvae and adults of the lesser mealworm, Alphitobius diaperinus Panzer, in laboratory choice and no-choice tests was studied. The compounds were synthesised from racemic and enantiomerically enriched (ee = 91-98%) cis- and trans-piperitols, which were obtained from (±)-piperitone. RESULTS Structure-activity relationship studies identified several synthetic halolactones with a very strong feeding deterrent activity. The most active were the enantiomeric chlorolactones with chiral centre configurations (1S,4S,5R,6R) and (1R,4R,5S,6S) and their racemic mixture. The racemic bromo- and iodolactones obtained from cis-piperitol and saturated lactones with a chiral centre configuration (1R,4S,6R) were also very good antifeedants in comparison with piperitone. Most of the studied compounds were better antifeedants against adults than against larvae-among the 21 compounds, only one bromolactone with a chiral centre configuration (1S,4R,5R,6R) was a weaker deterrent for adults. CONCLUSION Chemical transformation of the piperitone molecule by the introduction of a lactone function and a halogen atom strongly changed its antifeedant properties against the lesser mealworm. Optimum activity is dependent on the presence of a chlorine atom at C-5 of the cyclohexane ring. The activity of bromo- and iodolactones depended strongly on the chiral centre configuration and the halogen substituent.

Chemical composition and insecticidal activity of Thuja occidentalis and Tanacetum vulgare essential oils against larvae of the lesser mealworm, Alphitobius diaperinus

The chemical composition of the essential oils (EOs) of Thuja occidentalis L. (Cupressaceae) and Tanacetum vulgare L. (Asteraceae), obtained by steam distillation, and their insecticidal activity against larvae (10 and 20 days old) of the lesser mealworm, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae), were studied. The activity of the oils was compared with the activity of their major components, α‐ and β‐thujone. Isolation, identification, and quantification of the volatile compounds were performed using a gas chromatograph (GC) coupled to a mass spectrometer (MS). The major components of T. occidentalis EO were the monoterpenoid ketones α‐thujone (69.8%), β‐thujone (9.5%), and fenchone (7.8%). The monoterpenoid alcohols terpinene‐4‐ol and p‐cymene‐8‐ol, and the diterpenoid beyerene were only present in low amounts (<3.0%). All other compounds occurred in traces. In contrast to the thuja oil, the main compounds found in the EO of T. vulgare were β‐thujone (61.0%), camphor (13.0%), and trans‐chrysanthenyl acetate (6.5%). The insecticidal activity of both EOs and pure monoterpenes incorporated into a diet as acetone solutions at a concentration of 10 mg ml−1 depended on the age of A. diaperinus larvae. Young larvae displayed a higher sensitivity toward the tested chemicals than older ones. The survival of 10‐day‐old larvae, their body mass gain, and pupation rate were affected. The growth and development of the older larvae were similar to those of the control. In all tests, there were no significant differences between the activities of the EOs and their major components.

Synthesis of β-damascone derivatives with a lactone ring and their feeding deterrent activity against aphids and lesser mealworms

Starting from β-damascone, six new lactones were obtained. The Claisen–Johnson rearrangement of allylic alcohol and halolactonization of γ,δ-unsaturated acid were the key steps of the presented synthesis. The structures of the new derivatives were determined by spectroscopic data. The antifeedant activity of β-damascone towards two insect species with different feeding habits and food preferences, i.e., the peach-potato aphid Myzus persicae (Sulz.) and lesser mealworm, Alphitobius diaperinus Panzer, was studied, as well as the biological consequences of structural modification of the starting substrate. The successive structural modifications of β-damascone that resulted in the greatest antifeedant activity towards M. persicae were the incorporation of a lactone moiety and concomitant presence of bromine in the side chain. All β-damascone derivatives with a lactone moiety deterred the feeding of adults and larvae of A. diaperinus. Halo-δ-lactones were more active than halo-γ-lactones, and A. diaperinus adults were more sensitive to the compounds studied than larvae.

Synthesis and Antifeedant Activity of Racemic and Optically Active Hydroxy Lactones with the p-Menthane System.

Two racemic and two enantiomeric pairs of new δ-hydroxy-γ-lactones based on the p-menthane system were prepared from racemic and optically active cis- and trans-piperitols. The Johnson-Claisen rearrangement of the piperitols, epoxidation of the γδ-unsaturated esters, and acidic lactonization of the epoxy esters were described. The structures of the compounds were confirmed spectroscopically. The antifeedant activities of the hydroxy lactones and racemic piperitone were evaluated against three insect pests: lesser mealworm, Alphitobius diaperinus (Panzer); Colorado potato beetle, Leptinotarsa decemlineata (Say); and peach-potato aphid, Myzus persicae (Sulz.). The chemical transformation of piperitone by the introduction of a lactone moiety and a hydroxy group changed its antifeedant properties. Behavioral bioassays showed that the feeding deterrent activity depended on the insect species and the structure of the compounds. All hydroxy lactones deterred the settling of M. persicae. Among chewing insects, the highest sensitivity showed A. diaperinus adults.

Chemical composition, antimicromicrobial activity and insecticidal activity against the lesser mealworm Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) of Origanum vulgare L. ssp. hirtum (Link) and Artemisia dracunculus L. essential oils

BACKGROUND Essential oils (EOs) from Artemisia dracunculus L. and Origanum vulgare L. ssp. hirtum were obtained and the qualitative and quantitative chemical composition of the extracts was investigated. The insecticidal activity of EOs against the larval stages of Alphitobius diaperinus (Panzer) was studied. Moreover, the antimicrobial activity of these oils against pathogens transmitted by this pest was also investigated. RESULTS The obtained results indicate the possibility of using Greek oregano EO with a high content of carvacrol as a feed additive in poultry nutrition. The use of the Greek oregano oil at 1% (w/w) dose showed stronger reduction of body weight gain of stage IV larvae. Their body mass was only 10.92% of the control. Moreover, EOs from O. vulgare strongly inhibited the growth of tested bacterial strains as well as Candida albicans. CONCLUSION Greek oregano EO may be a good alternative to antibiotic growth promoters and coccidiostats whose use in feeding farm animals has been prohibited since January 2006 under European Union directives. The introduction of O. vulgare L. ssp. hirtum EO into the premises of farm and poultry houses may help to improve sanitary conditions and control of the lesser mealworm inhabiting these buildings.

Alkyl-Substituted δ-Lactones Derived from Dihydrojasmone and Their Stereoselective Fungi-Mediated Conversion: Production of New Antifeedant Agents.

A chemoenzymatic method was applied to obtain optically pure alkyl-substituted δ-lactones. First, chemical Baeyer–Villiger oxidation of dihydrojasmone (1) was carried out, affording two new alkyl-substituted δ-lactones: 3,4-dihydro-5-methyl-6-pentyl-2H-pyran-2-one (2) and 5-methyl-6-pentyl-1,13-dioxabicyclo[4.1.0]heptan-2-one (3). In the next step, fungal strains were investigated as biocatalysts to enantioselective conversion of δ-lactones (2) and (3). The fungal cultures: Fusarium culmorum AM10, Fusarium equiseti AM15 and Beauveria bassiana AM278 catalyzed the stereoselective hydration of the double bond of lactone (2) (ee = 20%–99%) while Didymosphaeria igniaria KCh6670 proved to be the best biocatalyst for the reduction of carbonyl group in the epoxylactone (3) (ee = 99%). In both cases, chiral oxyderivatives were obtained in low to high yields (7%–91%). The synthetic lactones (2), (3) and its derivatives (4), (5) were tested for their antifeedant activity towards larvae and adults of lesser mealworm (Alphitobius diaperinus Panzer) and peach potato aphid (Myzus persicae [Sulzer]) and some of them were active towards studied insects.

Microbial Hydrolysis of Racemic β-Aryl-γ-ethylidene-γ-lactones and Antifeedant Activity of the Products against Alphitobius diaperinus Panzer

Hydrolysis of (±)-β-aryl-γ-ethylidene-γ-lactones by fungal strain Aspergillus ochraceus AM370 afforded (−)-(S)-γ-ethylidene-γ-lactones 2a–d and (+)-(R)-γ-ketoacids 3a–d. Enantiomeric purity of the unreacted lactones was strictly related to a size of an aryl substituent at C-4 of γ-lactone ring, with the highest ee (77%) obtained for the (−)-(S)-γ-ethylidene-γ-lactone possessing unsubstituted benzene ring (2a) and the lowest one (15%) determined for the (−)-(S)-γ-ethylidene-γ-lactone with bulky 1,3-benzodioxole system (2d). Lactones 2a–d, both racemic and enantiomerically enriched, as well as products of their hydrolysis showed varying degrees of feeding deterrent activity against lesser mealworm, Alphitobius diaperinus Panzer, which depended on the structure of the compound and the developmental stage of the lesser mealworm. In the case of adults, more active were γ-lactones 2a–d, compared with ketoacids 3a–d. Only in the case of lactone 2a was the effect of configuration of stereogenic center on the activity found. Particularly strong deterrents against this stage (T > 180) were racemic and (−)-(S)-γ-ethylidene-γ-lactone with p-methoxysubstituted phenyl ring (2c).