Wally M. Blaney

Behavioral and electrophysiological study of antifeedant mechanisms associated with polyhydroxy alkaloids

Eleven polyhydroxy alkaloids of plant origin were tested for anti-feedant effects against larvae of the lepidopteransSpodoptera littoralis, Spodoptera frugiperda, Heliothis virescens, andHelicoverpa armigera. Data from behavioral and electrophysiological investigations were correlated to reveal information on the mode of action of the antifeedants. The pyrrolidine DMDP was an effective antifeedant for all four species, whereas the piperidines fagomine and XZ-1 and the pyrrolizidine alexine were all ineffective as antifeedants. The activity of the pyrrolidines CYB-3 and DAB-1, the piperidines DNJ, DMJ, and BR1, and the bicyclic octahydroindolizine castanospermine varied among species. The investigation focuses on the structural similarities between some of the alkaloids and some common phagostimulatory sugars and illustrates a neural interaction involving the neurons that are differentially responsive to alkaloids and sugars. InS. littoralis, the neurons responding specifically to the alkaloids DMDP, DAB-1, and castanospermine and to the sugars fructose, sucrose, and glucose are more active when the compounds are applied singly than when an alkaloid and a sugar are applied together. The implications for the occurrence and functioning of different sugar receptor sites are discussed.

Neo-clerodane insect antifeedants from Scutellaria galericulata

Abstract Four neo-clerodane diterpenoids have been isolated from aerial material of Scutellaria galericulata . Three compounds, jodrellin T, 14,15-dihydrojodrellin T and galericulin, are novel structures. The fourth, jodrellin B has been previously isolated from Scutellaria woronowii . Jodrellin B is amongst the most potent neo-clerodane antifeedants so far described, 14,15-dihydrojodrellin T is also active. Chemical structures were rigorously determined by spectroscopic methods.

Synthesis of biologically active drimanes and homodrimanes from (−)-sclareol

Abstract Three drimanes, polygodial (2), albicanyl acetate (3) and 7-oxo-8,12-drimen-11-al (5), and two homodrimanes, 13,14,15,16-tetranorlabd-7-en-12,17-dial (6) and 7-oxo-13,14,15,16-tetranorlabd-8(17)-en-12-al (7), were synthesized from (−)-sclareol (1), and their antifeedant, antitumor and antimicrobial properties tested. In most cases, 6 and 7 were found to be more active than 2.

Insect antifeedant activity associated with compounds isolated from species ofLonchocarpus andTephrosia.

The antifeedant activity of a series of 21 chalcones, flavanes, and flavanones isolated from the generaLonchocarpus andTephrosia (Leguminosae) was assessed by behavioral and electrophysiological bioassays against larvae ofSpodoptera littoralis andS. exempta. The antifeedant activity is related to the molecular structure of the compounds, and possible modes of interaction with the insect taste receptors are discussed.

The structure of two new clerodane diterpenoid potent insect antifeedants from Scutellaria woronowii (Juz); Jodrellin A & B

Abstract Two new clerodane diterpenoids isolated from Scutellaria woronowii (Juz) were shown to be the most potent clerodane antifeedants yet discovered. Their structures were rigorously determined by 1 H, 13 C, nuclear Overhauser difference 1-D, 1 H COSY 2-D n.m.r. and mass spectroscopy.

Insect antifeedants from azadirachta indica (part 5): Chemical modification and structure-activity relationships of azadirachtin and some related limonoids

Abstract Chemical modification of the potent insect antifeedant and growth-disruption agent azadirachtin (1) and the related limonoids 3-tigloyl azadirachtol (6) and salannin (27) have permitted an exploration of the biological activity of these compounds. General comments are made regarding the structural dependency of the antifeedant effect.

Bioactive sesquiterpenes from Santolina rosmarinifolia subsp. Canescens. A conformational analysis of the germacrane ring

The hexane extract of aerial parts of Santolina rosmarinifolia subsp. canescens afforded eight new sesquiterpenes in addition to known compounds. Their structures were determined by spectroscopic methods and chemical transformations. The conformational analysis of the germacrane constituents was carried out by spectroscopic methods, including NMR at varying temperature and by molecular mechanics calculations. The antifeedant, antibacterial and antitumoral activity of selected compounds has been tested.

The identification and characterization of resistance in wild species of Arachis to Spodoptera litura (Lepidoptera: Noctuidae)

Fourteen wild species of Arachis (Leguminosae) were investigated under field and laboratory conditions to evaluate their effect on the survival and development of the larvae of Spodoptera litura (Fabricius). All of the species studied were observed to be resistant compared to the susceptible control, Arachis hypogaea (genotype TMV2). Overall, the mortality and development of larvae recorded in the field were similar to those recorded for larvae on excised leaves of the same species in the laboratory. When neonate larvae were exposed to excised leaves of A. batizogaea, A. kemph-mercadoi, A. appresipila, A. paraguariensis, A. stenophyla and A. villosa mortality was greater than 94% compared to less than 20% on TMV2. Third stadium larvae lost weight when exposed to both field plants and excised leaves of eight of the wild species, whereas larvae feeding on TMV2 gained weight. When third stadium larvae were fed pulped leaves they gained more weight than when exposed to intact leaves, except in the case of A. chacoensis and Arachis spp. 30007. A penetrometer was used to determine the relative toughness of the leaves. The leaves of most of the wild species were shown to require a greater biting effort for feeding than the leaves of TMV2. There was a negative correlation between toughness of whole leaves and larval development. Observations of larval behaviour indicated that, overall, larvae were deterred from feeding on the leaves of the wild species. Diets containing the chemical extracts of dried leaves of A. kemph-mercadoi, A. paraguariensis, A. appresipila, A. chacoensis, A. glabrata and A. pseudovillosa resulted in low larval weight gain. The physical quality of the leaves and foliar chemicals are implicated as being responsible for the observed resistance. The implications and potential applications of these results are discussed.

Effect of Clerodane‐Type Diterpenoids Isolated from Salvia spp. on the Feeding Behaviour of Spodoptera littoralis

Twenty-nine clerodane-type diterpenoids isolated from species of Salvia growing in Mexico, or analogues of them, were tested for antifeedant activity against Spodoptera littoralis larvae using behavioural and electrophysiological bioassays. Eight of the compounds showed potent antifeedant activity in choice and no-choice bioassays and these compounds also stimulated dose-dependent responses from neurones in the lateral styloconic sensilla of S. littoralis.

Neo-clerodane diterpenoid insect antifeedants from Ajuga reptans cv catlins giant

Abstract Three new neo -clerodane diterpenoids (14,15-dehydroajugareptansin, 3β-hydroxyajugavensin B and 3α-hydroxyajugamarin F4), have been isolated from aerial parts of Ajuga reptans cv Catlins Giant, together with the known compound, ajugareptansin. The structures were determined by 1 H and 13 C NMR spectroscopy and MS. Insect antifeedant testing of all four compounds revealed that 14,15-dehydroajugareptansin had significant activity against sixth stadium larvae of Spodoptera littoralis .