Limonoids, Phenolics, and Furanocoumarins as Insect Antifeedants

Chapter 10

Limonoids, Phenolics, and Furanocoumarins as Insect Antifeedants, Repellents, and Growth Inhibitory Compounds

Downloaded by MICHIGAN STATE UNIV on March 1, 2013 | http://pubs.acs.org Publication Date: February 23, 1989 | doi: 10.1021/bk-1989-0387.ch010

James A. Klocke, Manuel F. Balandrin, Mark A. Barnby, and R. Bryan Yamasaki Native Plants, Inc. (NPI), University of Utah Research Park, Salt Lake City, UT 84108 Plants biosynthesize a dazzling array of structural types which exhibit an almost equally dazzling array of biological activities. In insects, various plant Compounds affect nerve axons and synapses (e.g., pyrethrins, nicotine, picrotoximn), muscles (e.g., ryanodine), respiration (e.g., rotenone, mammein), hormonal balance (e.g., juvenile andmoltinghormone analogs and antagonists ), reproduction (e.g., βasarone), and behavior (e.g., attractants, repellents, antifeedants). Some of these compounds have already been exploited in commercial insect control (e.g., pyrethrins, juvenile hormone analogs, attractants), while others offer a unique opportunity as sources and models of new insect control agents (1,2). Still others may be important components of host plant resistance mechanisms. This chapter will focus on the activity of certain plant compounds as insect antifeedant, repellent, and growth inhibitory compounds. Insect Antifeedants Antifeedants are substances which, when tasted by insects, result either temporarily or permanently, depending on potency, in the cessation of feeding (3). The existence of and potential for antifeedant compounds, both natural and synthetic, in practical insect control have been known for some time. For example, Bordeaux Piixture (copper sulfate, hydrated lime, and water), known for over 100 years, acts as a feeding deterrent to flea beetles, leaf hoppers, and the potato psyllid (Paratrioza çod95% o f u n t r e a t e d d i s k s w e r e e a t e n i n " c h o i c e " a s s a y s ( T a b l e I ) . I n f i e l d s t u d i e s c o n d u c t e d i.n o u r c o l l a b o r a t i o n w i t h a. m a j o r U.S. c h e m i c a l c o m p a n y , a z a d i r a c h t i n w a s f o u n d t o b e s y s t e m i c m c o r n a n d t o b e e f f e c t i v e a s a p r o p h y l a c t i c a g a i n s t S. lil^y^Çife t lb/ha. A z a d i r a c h t i n i s l e s s p o t e n t , a g a i n s t some o t h e r s p e c i e s o f insects. F o r example, a g a i n s t t h e Colorado potato b e e t l e , ^ P Î À n ^ t ^ J T ^ d e c e m l i n e a t a ( C h r y s o m e l i d a e ), 6 0 ug/cm/ o f a z a d i r a c h t i n r e s u l t e d i n - 5 % o f t r e a t e d [.«otalo l e a f d i s k s b e i n g e a t e n , w h i l e >50% o f u n t r e a t e d d i s k s w e r e e a t e n i.n " c h o i c e " a s s a y s (Table I ) . Two d e r i v a t i v e s o f a z a d i r a c h t i n , 2 2 , 2 3 - d i h y d r o a z a d i r a . c h t i n . a n d 2 , 3 , 2 2 , 2 3 - t e t r a h y d r o a z a d i r a c h t i η ( F i g u r e .1), w e r e p r e p a r e d a c c o r d i n g t o Yamasaki and Klocke (20) and t e s t e d a s a n t i f e e d a n t s a q a i n s t S. f r u g i p e r d a a n d L. d e c e m l i n e a t a . Similar t o our results w i t h t h e s e compounds a s g r o w t h i n h i b i t o r s a n d t o x i c a n t s t o t h e t o b a c c o budworm, H e l i o t h i s y i r x ^ c e n s ( N o e t u i d a e ) ( 2 0 ) , t h e s e t w o d e r i v a t i v e s were a s a c t i v e a s a z a d i r a c h t i n i t s e l f a s a n t i f e e d a n t s a g a i n s t S. f r i j g i r ^ r d a ( T a b l e I ) . H o w e v e r , a s a n t i f e e d a n t s a g a i n s t . L. d e c e m l m e a t a , t h e t w o d e r i v a t i v e s w e r e L e s s a c t i v e t h a n a z a d i r a c h t i n (Table I ) . Therefore, s t r u c t u r e - b i o a e t i v i t y r e l a t i o n s h i p (SAR) s t u d i e s i n v o l v i n g a z a d i r a c h t i n a s a n i n s e c t a n t i f e e d a n t s h o u l d be c o n d u c t e d w i t h s e v e r a l s p e c i e s o f j n s e e t s s i n c e t h e r e s p o n s e o f e a c h s p e c i e s t o i n d i v i d u a l d e r i v a t i v e s may differ. Some a t t e m p t s h a v e b e e n made t o d e f i n e t h e SAR o f a z a d i r a c h t i n as an a n t i f e e d a n t . F o r example, t h e furopyran moiety o f a z a d i r a c h t i n h a s b e e n s u s p e c t e d b y some? t o te t h e a c t i v e c e n t e r responsible f o r t h e antifeedant a c t i v i t y (21). However, P f J i e g e r a n d M u c k e n s t u r m ( 2 1 ) f o u n d n o a n t i f e e d a n t a c t i v i t y w i t h 9h v d r o x y d i h y d r o f u r o - 2 , 3 - p y r a n a g a i n s t , t h e E g y p t i a n c o t t o n l e a f worm, Spodoptera l i t t o r a l i s (Noctuidae). On t h e o t h e r h a n d , tey e t a l . (22) r e p o r t e d t h a t a n o v e l h y d r o x y d i h y d r o f u r a n a c e t a l , which represents a fragment o f a z a d i r a c h t i n , i s nearly as potent as a z a d i r a c h t i n a s a n a n t i f e e d a n t a q a i n s t S. J i t t o r a l i s . I n a d d i t i o n t o i t s a n t i f e e d a n t e f f e c t s , a z a d i r a c h t i n i s a. s l o w a c t i n g i n s e c t i c i d e because i t d i s r u p t s t h e hormonal b a l a n c e i n c e r t a i n s p e c i e s o f i n s e c t s w h e n i n g e s t e d (1_,23)» P r e l i m i n a r y d a t a in our laboratory indicate that azadirachtin inhibits the release o f i n s e c t b r a i n hormone ( p r o t h o r a c i c o t r o p i c hormone). 2

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O u r i n t e r e s t i n i n s e c t o v i p o s i t iona.1. r e p e i l e n t s s t e r n s f r o m r e c e n t i n v e s t i g a t i o n s i n our laboratory on t h e b i o l o g i c a l l y a c t i v e v o l a t i l e o i l o f the tarweed, ^ m i z o a i a f i t c h i i (Asteraceae) ( 2 4 ) . F r o m H. f i t c h i i v o l a t i l e o i l , we i s o l a t e d t h e n i o n o t e r p e n o i d , 1,8cineole (Figure 2). We f o u n d t h a t t h i s c o m p o u n d e x h i b i t s i n s e c t f e e d i n g a n d o v i p o s i t i o n a l r e p e l l e n t a c t i v i t i e s a g a i n s t t h e y e 1 .low f e v e r mosquito, Aedes a e g y p t i ( C u l i e i d a e )( 2 5 ) .

In Insecticides of Plant Origin; Arnason, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

INSECTICIDES OF PLANT ORIGIN

140

T a b l e 1. A n t i f e e d a n t A c t i v i t y o f A z a d i r a c h t i n a n d Two D e r i v a t i v e s i n " C h o i c e " L e a f D i s k A s s a y s A q a i n s t Sp::doptera f r u ^ i j ^ d a I^Et^PÎ.arsa d e c e m l i n e a t a


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P C ^ i s t h e m i n i m u m p r o t e c t i v e c o n c e n t r a t i o n o f c o m p o u n d (yg/'onr ) a t w h i c h 95% o f u n t r e a t e d l e a f d i s k s , a r eeaten i n a " c h o i c e " assay. to

P C ο i s t h e minimum p r o t e c t i v e c o n c e n t r a t i o n o f compound (yg/cm-) a t w h i c h o f t r e a t e d p o t a t o l e a f d i s k s , w h i l e >50% o f u n t r e a t e d leaf d i s k s , a r eeaten i na "choice" assay. 5



KLOCKE ET AL.

Limonoids, Phenolics, and Furanocoumarins

THYMOL

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P-CYMENE

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EUGENOL

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Figure 2. Chemical structures of the cxarpounds tested for mosquito ovipositional repellent activity.


INSECTICIDES OF PLANT ORIGIN

142


I n t h e p r e s e n t s t u d y r we h a v e e x p a n d e d o u r i n v e s t i g a t i o n o f biologically active plant v o l a t i l e o i l constituents to include s e v e r a l o t h e r n a t u r a l l y o c c u r r i n g compounds, namely eugenoJ, t h y m o l , c a r v a c r o l , and t r a n s - c i n n a m a I d e h y d e , on the b a s i s o f a v a i l a b i l i t y and known b i o l o g i c a l a c t i v i t y ( F i g u r e 2 ) , For example, eugenol i s used c o m m e r c i a l l y as an a t t r a c t a n t f o r the Japanese beetle, P o p i i l i a j a p o m c a (Scarahaeidae) (2). Thymo! a n d c a r v a c r o l a r e known a n t i s e p t i c and a n t h e l m i n t i c a g e n t s and t r a n s cinnama.Idehyde i s u s e d i n f l a v o r i n g ( 2 6 ) . p - C y m e n e was i n c l u d e d i.n t h i s s t u d y because o f i t s s t r u c t u r a l s i m i l a r i t y t o thymol and c a r v a c r o l , and Deet ( N , N - d i e t h y l - m - t o l u a m i d e ) , a c o m m e r c i a l l y a v a i l a b l e i n s e c t r e p e l l e n t , was i n c l u d e d a s a s t a n d a r d ( F i g u r e 2 ) . G r a v i d A. a e g y p t i f e m a l e s were? g i v e n a c h o i c e o f o v i p o s i t i n g o n p a p e r t o w e l i n g l i n i n g g l a s s c r y s t a l l i z i n g d i s h e s (70 χ 50 mm) c o n t a i n i n g e i t h e r t a p w a t e r o r one o f t h e t e s t compounds i n t a p w a t e r a t a c o n c e n t r a t i o n r a n g i n g f r o m 0 . 0 1 - 0 . 8 % w/v (25). Eggs l a i d i n t h e d i s h e s w e r e c o u n t e d and r e s u l t s a r e g i v e n i n T a b l e I I as t h e n u m b e r o f e g g s l a i d i n t h e t r e a t e d d i s h e s d i v i d e d b y the* n u m b e r o f e g g s l a i d i n t h e c o n t r o l d i s h e s , m u l t i p l i e d by 100 (T/C χ 1 0 0 % ) . F r o m T a b l e I I , i t i s a p p a r e n t t h a t , a s A. a e g y p t i o v i . p o s i t i o n a l r e p e l l e n t s , the r e l a t i v e a c t i v i t y of thymol-carvacrol - transc i n n a m a I d e h y d e - e u g e n o l >Deet. i , 8 - e i n e o i e > p - e y m e n e . E v e n at. t h e l o w e s t c o n c e n t r a t i o n t e s t e d ( 0 . 0 1 % ) , t h y m o l , c a r v a c r o l , and t r a n s cinnama Idehyde were e f f e c t i v e o v i p o s i t i o n a i repellents. Eugenol was l e s s e f f e c t i v e , y e t was a s a c t i v e a t 0 . 0 1 % «as Deet was a t 0.2%. 1 , 8 - C . i n e o i e was s l i g h t l y l e s s a c t i v e t h a n D e e t . In general, the o x y g e n a t e d a r o m a t i c compounds were more e f f e c t i v e t h a n t h e o x y g e n a t e d c y c l o a l i p h a t i c compound, 1,8-cineo.le. p-

Limonoids, Phenolics, and Furanocoumarins as Insect Antifeedants

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