13-Deoxyitol A, a new insecticidal isoryanodane diterpene from the seeds of Itoa orientalis
A new isoryanodane diterpene, 13-deoxyitol A (1), together with a known isoryanodane diterpene, itol A (2), was isolated from the methanol extract of the seeds of Itoa orientalis. Its structure was determined by spectroscopic means. Compounds 1 and 2 showed antifeedant and contact toxic activities against various insect pests.
[Show abstract] [Hide abstract] ABSTRACT: Background Destructive impacts of insecticides on non targeted populations necessitate the development of an eco friendly pest control method. Streptomyces spp. are rich source of bioactive secondary metabolites which may provide valuable alternatives to chemical insect-control agents as they can be less toxic and readily biodegradable. Because of its potent biocontrol attributes, ethyl acetate extract of Streptomyces hydrogenans DH16, a soil isolate, was tested to assess its anti-insect potential against polyphagous noctuid, Spodoptera litura.ResultsThe secondary metabolites in the ethyl acetate extract of S. hydrogenans DH16 exhibited larvicidal and growth inhibitory activities. The results indicated that highest concentration of 1600 ¿g/ml was significantly effective as 70% larval, 66.66% prepupal and 100% pupal mortality was noticed. The metabolites also prolonged the larval developmental period. The LC50 and LC90 values were 1337.384 and 2070.516 ¿g/ml, respectively for the insect. Negative effects of S. hydrogenans were also observed on development of the insect. Significant decline in adult emergence, adult longevity, fecundity and % hatching was recorded at higher concentrations along with morphological abnormalities as compared to control. Significant decrease in relative growth and consumption rate, efficiency of ingested and digested food and increase in approximate digestibility in larvae reared on diet supplemented with ethyl acetate extract accounts for the toxic as well as anti-nutritive nature of extract.Conclusion Secondary metabolites in the fermentation broth from S. hydrogenans were toxic to the larvae at higher concentrations whereas lower concentrations significantly reduced the reproductive potential of S. litura. Therefore, these metabolites show considerable potential for incorporation in pest management programmes as new biopesticidal formulation.0Comments 1Citation
- "Natural products obtained from plants and microorganisms have been used for insect control . Azadirachtin (complex limonoids), a natural compound isolated from Indian neem tree, Azadirachta indica A. Juss (Meliaceae), is known to have lethal effects on more than 400 insect species  and many workers have used azadirachtin as positive control121314 . Recently, microbial insecticides have attracted considerable attention  because they are more specific, have low relative cost and are more eco-friendly161718. "
[Show abstract] [Hide abstract] ABSTRACT: Background Considerable attention has been paid to actinomycetes, especially the secondary metabolites obtained from Streptomyces species, as the best alternatives to chemicals as biological control agents for polyphagous pests such as Helicoverpa armigera and Spodoptera litura. On the basis of their novel biocontrol attributes, novel polyketide metabolite isolated from marine Streptomyces sp. AP-123 exhibited significant antifeedant, larvicidal and growth inhibitory activities against polyphagous pests. Results Leaf disc no-choice method was used for the insect bioassay. The polyketide metabolite presented significant antifeedant activities against H. armigera (78.51%) and S. litura (70.75%) at 1000 ppm concentration. The metabolite also exhibited high larvicidal activities against H. armigera (63.11%) and S. litura (58.22%) and the LC50 values were 645.25 ppm for H. armigera and 806.54 ppm for S. litura. The metabolite also prolonged the larval–pupal duration of the insects at all the tested concentrations. Conclusions The activities of the polyketide metabolite were concentration dependent for both the insects therefore it could be used as an agent to prepare new pesticidal formulations.0Comments 10Citations
- "Fortunately, biopesticides have been gaining increased attention and interest among those concerned with developing environment friendly and safe integrated crop management, with compatible approaches and tactics for pest man- agement . Natural products derived from plants and microorganisms have been used for insect control . Azadirachtin, a natural compound isolated from neem Azadirachta indica, is considered superior over other compounds since it has wide range of biological activities. "
- "Azadirachtin , a natural compound isolated from neem Azadirachta indica , is considered superior over other compounds since it has wide range of biological activities. In the past many workers have used azadirachtin as positive control (Koul et al., 2005; Tewary et al., 2006; Tang et al., 2009; Jeyasankar et al., 2011 ). Bacterial and viral-based insecticides controlled different pests (Nagarkatti, 1982 ). "