Insect antifeedant activity

A SN reaction-based domino route to clerodane diterpenoid tanabalin (2-488) [258] has been described by Watanabe s group (Scheme 2.111) [259]. This natural product is interesting as it exhibits potent insect antifeedant activity against the pink bollworm, Pectinophora gossypiella, a severe pest of the cotton plant The domino sequence towards the substituted trans-decalin 2-487 as the key scaffold is induced by an intermolecular alkylation of the (5-ke toes ter 2-484 with the iodoalkane 2-483 followed by an intramolecular Michael addition/aldol condensation (Robin-... 

Figure 1. Clerodanes with insect antifeedant activity.

Limonoids are C2(, nortriterpenoids deriving from a C30 triterpene precursor. The best known limonoids are the Azadirachta indica (neem tree) antifeedant azadirachtin (C50L C40 C6 -C60(epoxide methylene cross-link) furan) and the Citrus species (Rutaceae) bitter antifeedant limonin (G50L G40 G6 G6 C50L(epoxide)-furan). Limonin gives a delayed bitter taste to Citrus fruit. The limonoids are typically bitter compounds with insect antifeedant activity... 

Insect Antifeedant Activity. It has been recognized that iminosugars such as 1-deoxynojirimycin 2, homonojirimycin 85 (Figure 9.29) and deoxymannojirimycin 59 markedly affect the maturation and feeding behavior of a number of economically significant pest insects,... 

Tetranortriterpenoids.—The cytotoxic or insect antifeedant activity shown by various tetranortriterpenoids ensures that the isolation and structure determination of these often complex molecules continue to attract attention. A detailed examination of the seeds of Azadirachta indica (Meliaceae) has yielded the further tetranortriterpenoids (76)—(81). The stereochemistry of 7-acetylneotrichilenone (78)... 

Darwish el al. (1980) described the insect antifeedant activity of quaternary derivatives of some commercially available heterocyclic secondary amines. The most active members of this series, tested against Leptinotarsa decemlineata, were compounds 4 and 5. 

In summary, the Delphinium diterpene alkaloids cardiopetamine (30) and 15-acetylcardiopetamine (27) are potent insect antifeedants active on two insect species with different feeding adaptations (a polyphagous Lepidopteran and an oligophagous Chrysomelid beetle), suggesting a potential broad range of antifeedant action for this class of compounds [20]. 

In a previous paper [1], we reviewed the isolation of quassinoids, alkaloids, and fatty acids from Simaroubaceous plants during the period 1972-1988 and discussed their biological activities, such as antitumor, antimalarial, and anti-inflammatory agents as well as insect antifeedants, amoebicides, and herbicides. This review will add new quassinoids isolated from Simaroubaceous plants from 1988 onwards and their biological activities, for example, antitumor, anti-tumor-promotor (= inhibitor against TPA-induced EBV-EA activation), anti-HIV, anti-tuberculosis, and insect antifeedant activities. Furthermore, the stability of quassinoids, lower activities of degradation products, and the synthesis of fluorinated quassinoids are also described. 

Teucrium species are used in folk medicine as diuretic, diaphoretic, carminative, astringent, stimulant and tonic, antiseptic, antipyretic and antiinflammatory agents. T. cubense [92] for example is used against stomach aches and as an amoebacide. Teucjaponin A(32) obtained from T. japonicum [33] was shown to be antifeedant for the larve of Prodenia litura. Its threshold concentration for inhibitory activity was about 400 ppm in the leaf disk test. Generally neo-clerodane diterpenes posses insect antifeedant activity and they are used as antifungal, antitumor and antibacterial agents [56,63]. The antitumor activity of T. bicolor [52] was reported. The antifeedant activity of neoclerodanes is mentioned in a... 

The insect antifeedant activity of root bark powders and ethanol extracts of C. angulatus against the cruciferous leaf beetle, Colaphellus bowringi was recorded in 1936 and since then a body of work on the activity of the extract against several insect species has been carried out [128]. This finding prompted several scientific groups to initiate an extensive research on this species to extract the active components. 

The first scientific paper dealing with a non-alkaloid sesquiterpene polyol ester showing insect antifeedant activity was published by Wakabayashi et al. [128], who reported that celangulin (1), isolated from the ethyl ether extract of Chinese bittersweet root bark, exhibited activity against Spodoptera frugiperda (Noctuidae, Lepidoptera) larvae. Thus, addition of the compound in the diet at a concentration of 5 and 10 ppm, the average body weight of larvae was reduced to 61% and 37%, respectively. 

In the course of a search for novel insect antifeedant and insecticidal compounds, Tu et al. isolated compound 11 (50% death rate) from Celastrus gemmatus Loes and compound 12 (49% antifeedant rate) from Celastrus rosthornianus Loes, which showed effects against the larvae of P. rapae [133, 134], Celastrus flagellaris have also yielded sesquiterpenes with insect antifeedant activity and a preliminary test of the Me2CO solutions of compounds 13 and 14 (500 mg/1) against M. separata... 

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