DOI: 10.5176/978-981-08-8119-1_BioTech2011_7
Authors: Dr. Smita Srivastava and Dr. A. K. Srivastava
Abstract:
Azadirachtin, a well known biopesticide, is a secondary metabolite conventionally extracted from the seeds of Azadirachta indica. Present study involves the production of azadirachtin under in vitro conditions by developing hairy roots of Azadirachta indica. The bio-efficacy analysis of the crude azadirachtin extract from the hairy roots demonstrated high amount of anti-feedant activity (antifeedant index (A.I) : 83.5 {6e6090cdd558c53a8bc18225ef4499fead9160abd3419ad4f137e902b483c465}
at concentrations as low as 0.05 {6e6090cdd558c53a8bc18225ef4499fead9160abd3419ad4f137e902b483c465} w/v in ethanol) against the desert locust Schistocerca gregaria (Forskal). The fact that azadirachtin is extremely liable to photodegradation due to the presence of light absorbing moieties in its chemical structure can limit its popular usage, despite having high bio-pesticidal activity.
Thus, in the present study, in order to extend the shelf life of azadirachtin, effect of various photostabilizers (tween-20, triton X-100, para-amino benzoic acid (PABA), anthraquinone, 8-hydroxy quinoline, ter-butyl hydroquinone) was investigated on the photo-stability enhancement of azadirachtin under controlled conditions (light: 5200 lux, temperature: 25 + 2 0C). These stabilizers generally prevent the pesticide molecule from photoexcitation through preferential light absorption or by energy and charge transfer from the excited pesticide molecule (upon photo energy absorption), thus, in either case, extending the shelf life of the photo-sensitive pesticide molecule. Azadirachtin in the presence and absence of the photostabilizers studied was found to follow a first order degradation kinetics. This was evident from the linearity of the plot between logarithmic concentrations of azadirachtin versus time with a regression coefficient value (R2) > 0.9. Hence, the effect of each stabilizer on the degradation of azadirachtin was evaluated on the basis of disappearance time DT50 (time taken to reduce the {6e6090cdd558c53a8bc18225ef4499fead9160abd3419ad4f137e902b483c465} azadirachtin to half of the original concentration in the sample).
Keywords: Azadirachtin; Hairy roots; Azadirachta indica; Antifeedant activity; Photodegradation; Photostabilizers; Disappearance time (DT50)
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