%0 Journal Article
%T Effects of Quinizarin and Five Synthesized Derivatives on Fifth Larval Instar Midgut Ecdysone 20-Monooxygenase Activity of the Tobacco Hornworm Manduca sexta
%A Christopher A. Drummond
%A Maria Teresa Molina
%A Sandra Taliansky
%A Carl R. Breidenbach
%A Carmen F. Fioravanti
%J International Journal of Zoology
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/261512
%X The plant allelochemical, quinizarin (1,4-dihydroxy-9,10-anthraquinone), and five anthraquinones that were synthesized from quinizarin, namely, 1,4-anthraquinone; 2-hydroxy-1,4-anthraquinone; 2-methoxy-1,4-anthraquinone; 9-hydroxy-1,4-anthraquinone; and 9-methoxy-1,4-anthraquinone, were assessed as to their effects on the essential, P450-dependent ecdysone 20-monooxygenase system of the insect model Manduca sexta (tobacco hornworm). This steroid hydroxylase converts the arthropod molting hormone, ecdysone, to the physiologically required 20-hydroxyecdysone form. M. sexta fifth larval instar midgut homogenates were incubated with increasing concentrations (10£¿8 to 10£¿3£¿M) of each of the six anthraquinones followed by ecdysone 20-monooxygenase assessments using a radioenzymological assay. Four of the five anthraquinones exhibited ¡¯s of about to £¿M. The most effective inhibitors were 2-methoxy-1,4-anthraquinone and 1,4-anthraquinone followed by 9-hydroxy-1,4 anthraquinone and 9-methoxy-1,4-anthraquinone. At lower concentrations the latter anthraquinone stimulated E20M activity. Quinizarin was less inhibitory and 2-hydroxy-1,4-anthraquinone was essentially without effect. Significantly, these studies make evident for the first time that anthraquinones can affect insect E20M activity, and thus insect endocrine regulation and development, and that a relationship between anthraquinone structure and effectiveness is apparent. These studies represent the first demonstrations of anthraquinones affecting any steroid hydroxylase system. ¡°This paper is dedicated with admiration to the legacy of Dr. Stan L. Smith, without whom this work and studies like it would not have been initiated.¡± 1. Introduction Ecdysone 20-monooxygenase (E.C. 1.14.99.22, E20M) is the insect cytochrome P450-dependent steroid hydroxylase responsible for the conversion of the arthropod molting hormone ecdysone (E) to its more active metabolite, namely, 20-hydroxyecdysone (20E) [1, 2]. The nature, regulation, and molecular biology of E20M were elucidated predominantly employing the tobacco hornworm, Manduca sexta, as the model [3¨C8]. Indeed, the developmental impact of E20M was made evident in midgut tissue of the M. sexta fifth larval instar where E20M activity increases 50-fold between days four and five of the stadium and this increase is inextricably tied to the onset of wandering stage behavior [1, 8, 9]. Moreover, the timing conferred by pulses of 20E was found to be critical to all stages of insect development [1, 10]. The E20M system, therefore, represents a crucial target in terms of
%U http://www.hindawi.com/journals/ijz/2014/261512/