• Journal of Applied Biological Chemistry
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• v.48 no.2
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• pp.65-74
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• 2005

Fungicidal, insecticidal, and mosquito larvicidal activities of piperidine alkaloids, pipernonaline and piperoctadecalidine, and isobutylamide alkaloids, pellitorine, guineensine, pipercide, and retrofractaminde A, derived from Piperaceae fruits were studied. Pipernonaline and piperoctadecalidine showed potent fungicidal activities against Puccinia recondita with 91 and 80% control values at 500 ppm. Against Phytophthora infestans, pipernonaline showed strong fungicidal activity with 91 and 80% control values at 1,000 and 500 ppm. $LD_{50}$ values of pipernonaline and piperoctadecalidine against Plutella xylostella were 125 and 95.5 ppm, respectively, and that of piperoctadecalidine against Tetranychus urticae was 246 ppm. Against larvae of Aedes aegypti and Culex pipiens pallens, $LD_{50}$ values of pipernonaline were 0.35 and 0.21 ppm, respectively. Highest larvicidal activities of pipercide and retrofractamide A were found against A. aegypti, A. togoi, and C. pipiens pallens. $LD_{50}$ values of pipercide and retrofractamide A were 0.10 and 0.039 ppm against A. aegypti, 0.26 and 0.01 ppm against A. togoi, and 0.004 and 0.028 ppm against C. pipiens pallens, respectively. Based upon these results and earlier findings, bioactive components derived from Piperaceae fruits may be valuable for development of useful lead product of possibly safer fungicidal, insecticidal, and mosquito larvicidal agents.

• Journal of Microbiology and Biotechnology
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• v.23 no.8
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• pp.1107-1115
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• 2013

The Cyt1Aa protein of Bacillus thuringiensis susbp. israelensis elaborates demonstrable toxicity to mosquito larvae, but more importantly, it enhances the larvicidal activity of this species Cry proteins (Cry11Aa, Cry4Aa, and Cry4Ba) and delays the phenotypic expression of resistance to these that has evolved in Culex quinquefasciatus. It is also known that Cyt1Aa, which is highly lipophilic, synergizes Cry11Aa by functioning as a surrogate membrane-bound receptor for the latter protein. Little is known, however, about whether Cyt1Aa can interact similarly with other Cry proteins not primarily mosquitocidal; for example, Cry2Aa, which is active against lepidopteran larvae, but essentially inactive or has very low toxicity to mosquito larvae. Here we demonstrate by ligand binding and enzyme-linked immunosorbent assays that Cyt1Aa and Cry2Aa form intermolecular complexes in vitro, and in addition show that Cyt1Aa facilitates binding of Cry2Aa throughout the midgut of C. quinquefasciatus larvae. As Cry2Aa and Cry11Aa share structural similarity in domain II, the interaction between Cyt1Aa and Cry2Aa could be a result of a similar mechanism previously proposed for Cry11Aa and Cyt1Aa. Finally, despite the observed interaction between Cry2Aa and Cyt1Aa, only a 2-fold enhancement in toxicity resulted against C. quinquefasciatus. Regardless, our results suggest that Cry2Aa could be a useful component of mosquitocidal endotoxin complements being developed for recombinant strains of B. thuringiensis subsp. israelensis and B. sphaericus aimed at improving the efficacy of commercial products and avoiding resistance.