Potent Insect Antifeedants from the African Medicinal Plant - American

12 Potent Insect Antifeedants from the African Medicinal Plant Bersama abyssinica ISAO K U B O and TAKESHI M A T S U M O T O

Downloaded by UNIV OF ROCHESTER on June 24, 2013 | http://pubs.acs.org Publication Date: April 26, 1985 | doi: 10.1021/bk-1985-0276.ch012

Division of Entomology and Parasitology, College of Natural Resources, University of California, Berkeley, C A 94720

The chemical investigation of pest insect control agents from the East African medicinal plant Bersama abyssinica (Melianthaceae) has led us to the i s o l a t i o n and characterization of four new bufadienolide steroids; abyssinin, abyssinol-A, -B, and -C. One of these, abyssinin, exhibits very strong antifeedant a c t i v i t y (PC =5µg/disk) against the cotton pest insect, Heliothis zea. This is one of the most potent antifeedants i s o l a t e d from botanical sources so f a r . 2D-COSY NMR was very useful i n the structural assignment of these insect antifeedants. 95

In the course of our search for pest insect control agents based on natural products our interests have focused upon plants which are not attacked by insects as these plants may produce defensive chemicals f o r deterring herbivory. An example i s the East African medicinal plant Bersama abyssinica (Melianthaceae), which i s widely used f o r various diseases such as dysentery, epilepsy and hemorrhoid. The extract from young twigs i s also drunk f o r the treatment of roundworm (1). In a preliminary experiment, using the l e a f disk bioassay wTth a glandless cotton c u l t i v a r (2), the root bark extract of EL abyssinica exhibited potent insect antifeedant a c t i v i t y against the important North American cotton insect pest Heliothis zea. The i s o l a t i o n of the active p r i n c i p l e s , guided by a l e a f disk TSToassay, produced the four bufadienolides a b y s s i n i n , abyssinol-A, - B , and -C as insect antifeedants. Their structures were established as (I), (II), (III) and (IV), respectively. The chemical components of abyssinica were previously examined by Kupchan (2). By monitoring the cytotoxic a c t i v i t y against KB tissue cultures four bufadienolides, (bersaldegenin 3-acetate (V), bersaldegenin 1,3,5-orthoacetate (VI), hellebrigenin 3-acetate (VII) and hellebrigenin 3,5-diacetate (VIII)) were isolated as active p r i n c i p l e s . However, none of these were detected by the bioassay methods used i n the present study. 0097-6156/85/0276-O183$06.00/0 © 1985 American Chemical Society

In Bioregulators for Pest Control; Hedin, P., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

BIOREGULATORS FOR PEST CONTROL


184


12.

KUBO AND MATSUMOTO

185

Insect Antifeedants

Isolation The fresh root bark (2 kg) of j * . abyssinica was c o l l e c t e d near Kakamega, Kenya, i n 1981, and extracted with aqueous methanol. The i s o l a t i o n scheme i s depicted in Figure 1. The crude extract was concentrated, and the residue was extracted with hexane, methylene c h l o r i d e , and ethyl acetate. The bioactive methylene chloride extract was chromatographed on s i l i c a g e l . A CHCI3-CH3OH (20 : 1) e l u t i o n gave crude abyssinin (200 mg). Further elution with CHCI3-CH3OH (10 : 1) gave a mixture of crude abyssinol A, B, and C (20 mg). This mixture was further separated by TLC ( S i 0 , CHCI3-CH3OH; 10 : 1) into the three fractions composed of crude abyssinol A, B, and C., r e s p e c t i v e l y . Each of the crude fractions of abyssinin, abyssinol A, B, and C s t i l l showed two spots with a c a . 1 : 1 r a t i o on TLC. The *H NMR spectra of these crude fractions indicated that each fraction contained two s t r u c t u r a l l y s i m i l a r compounds epimeric at C-17. The separation of these two components was troublesome because these were convertible to each other gradually under both normaland reversed-phase chromatographic conditions with a protic solvent such as methanol. Final p u r i f i c a t i o n of the crude of abyssinin was performed by f l a s h chromatography on s i l i c a gel using ether to give pure c r y s t a l l i n e abyssinin and 17-epiabyssinin. Similarly, pure abyssinol A, B, and C were separated from t h e i r C-17 epimers by s i l i c a gel TLC without the use of protic solvents. The ethyl acetate f r a c t i o n , which exhibited antimicrobial a c t i v i t y against B a d lus subtil i s other than antifeedant a c t i v i t y , was subjected to droplet counter current chromatography (DCCC) to g i v e , as the major compounds, g a l l i c acid (72 mg) and methylgallate (45 mg) as shown i n Figure 2.


2

Structure of abyssinin Abyssinin (I), M.P. 2 7 8 ° C (from EtOH), C27H30O8 (elemental a n a l y s i s ) , possess the following physical constants: Ε I - M S , m/z 482(M ), 454(M-C0), 439(M-C0CH3) and 422 (M-CH CÏÏC)rT); UV (EtOH) 228(ε 7700, s h . ) , 256 (ε 13400) and 296 nm (ε 7100, sh. ); CD (EtOH) 330(Δε+3.4) and 335 nmU +3.2, h . ); IR (CHCI3) 2850, 1735, 1724, 1710, 1643, 1630, 1545 and 1250 cm" . The C NMR data summarized in Figure 3a shows the presence of three CH3, six CH2, f i v e CH, three quaternary, six o l e f i n i c , and four carbonyl carbons. These r e s u l t s were based on a combination of; proton-noise decoupling (PND), continuous wave decoupling (CWD), and p a r t i a l l y relaxed Fourier transform (PRFT) techniques (4). The 400 MHz *H NMR data shown in Figure 3b were obtained mainly by 2D COSY techniques and by LIS experiments using Eu(fod)3. These spectral data showed abyssinin to be a bufadienolide type steroid (5-8) containing the following groups: an acetate ester (g), an aldehyde (b), and epoxide ( c ) , a quaternary methyl (d), a f u l l y substituted α-methoxy enone moiety (e), and an α-pyrone group ( f , x ax 296 nm, v 1710, 1630, 1545 cm" ) (see Figure 4 ) . The 2D NMR spectrum shown in Figure 5 indicates the three low f i e l d proton signals (7.30, 7.04 and 6.33 ppm) are coupled to each +

3

e

1

s

1 3

m

m a x

1


In Bioregulators for Pest Control; Hedin, P., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985. r

2

3

TLC (Si0 , CHCl -MeOH)

1

Abyssinol A (5 mg)

Abyssinol Β (3 mg)

Abyssinol (3 mg)

C

Abyssinol A Abyssinol Β Abyssinol C (containing their 17-epimers) I J I

17-Epiabyssinin (12 mg)

Flash column (Si0 . ether) 2

2

Column (Si0 , CHC^-MeOH)

Methylenechloride*

I

MeOH extract

3

T

C

2

Methyl gall ate (45 mg)

Ethyl acetate)

(Si0 , Petr. ether-

L

Gallic acid (72 mg)

ascending method)

2

Water

DCCC (CHCl -MeOH-H 0;7/13/8,

Ethyl acetate

(M«Hanthac«M)

Root bark (2 kg)

abyssinica

F i g u r e 1. I s o l a t i o n scheme f o r the f r e s h r o o t bark o f B. abyssinica.

Abyssinin (180 mg)

Oleanoic acid (300 mg)

I

1

n-Hexane

Bersama


73 Ο r

H n ο

co

m

*0

3

1

δ 73 m Ο c r


KUBO AND MATSUMOTO

Insect Antifeedants

F i g u r e 2. DCCC o f t h e e t h y l a c e t a t e e x t r a c t ( 1 . 2 g ) o f B. a b y s s i n i c a w i t h CHC1 -CH 0H-H 0 (7:13:8 v / v ) by t h e a s c e n d i n g method; 5 m l / f r a c t i o n . 3

3

2




21.4

Ilia [

1 3

C

NMR In CDCI3]

7.04(dd,9.8,2.5)

I

e.33(dd,e.e,0.8)

Illb [ H 1

ure 3.

13

MNR In C D C I ] 3

1 C NMR ( a ) and H NMR ( b ) d a t a f o r a b y s s i n i n .



Figure data.

4.

Groups c o n t a i n e d

8

b y a b y s s i n i n a s shown b y t h e

7

6

stacked plot

Figure

5.

189

Insect Antifeedants

KUBO AND MATSUMOTO

Two-diminsional

8

spectral

7 contour plot

NMR s p e c t r u m .


6 PPM


190

BIOREGULATORS FOR PEST C O N T R O L

other, and these signals were assigned to the protons on the α-pyrone moiety. The high f i e l d s h i f t of 22-H i n comparison with those of a l l known bufadienolides (6) i s probably due to a diamagnetic anisotropic e f f e c t caused by the C-16 carbonyl group. The broad s i n g l e t proton signal at 3.00 ppm was i d e n t i f i e d as 17-H by the presence of an a l l y l i c coupling (0.5 Hz) with 21-H (7.30 ppm). The contour plot shown i n Figure 6 also showed the presence of t h i s a l l y l i c coupling. S i m i l a r l y , a long-range coupling between the methyl s h i f t at 0.93 ppm and 17-H was observed in the 2D COSY spectrum shown in Figure 7, indicating their trans r e l a t i o n s h i p , and locating t h i s CH3 group at C-13. This relationship also confirmed the configuration of the α-pyrone ring to be β , and c i s to the I3-CH3. Upon c a t a l y t i c h y d r o g é n a t i o n (over 5 Pd/C i n ethanol), abyssinin absorbed two moles of hydrogen to give tetrahydroabyssinin (IX). Tetrahydroabyssinin (IX), C97H34O8,possessed the following physical properties: UY(EtOH), 248 nmU 9700); C0(10 dioxane/EtOH) 353Ue+3.4), 349 nm (Δε+3.2, s h . ) ; Ε Ι - M S m/z 486(M ); *H NMR(CDC1 ) 9.84(1H, s , 19-H), 4.62 (1H, t , J=l"3 Hz, 2 1 - H ) , 4.20(1H, dd, J=13, 4.5 Hz, 21-Hp), 3.78(3H, s , OCH3), 3.49(1H, d , J=3.5 Hz, 4-H), 3.41UH, b r . s , 3-H), 3.09(lH,dt,J=12, 4 H z , 6 - H ) , 3.02(1H, t d , J=10, 4Hz, 8-H), 2.74UH, ddd, J=15, 9, 6 Hz, 2 3 - H ) , 2.64(1H, dq, J=12, 4 Hz, 7 - H ) , 2.48(1H, d t , J=15, 6 Hz, 2 3 - H ) , 2.32 (1H, m, 20-H), 2 . 1 7 Î 1 H , ddd, J=12, 6, 3 Hz, 2 - H ) , 2.08 (1H, m, 6 - H ) , 2.03(3H, s , OCOCH3), 1.87(1H, d , 3 Hz, 17-H), 1.15(3H, +

3

a

e

a

e

e

e

a

s , I3-CH3).

The low f i e l d s h i f t U+0.22 ppm) of the I3-CH3 signal in going from I to IX, without any other group s h i f t i n g , supports the B-configuration of the pyrone group. A molecular model of I shows that the I3-CH3 group i s situated over the pyrone r i n g , and the s h i f t i s probably due to an anisotropic e f f e c t induced by a ring current of the pyrone moiety. The stereochemistry at position 17 i n I i s consistent with those of a l l bufadienolides known to date. The α-methoxy enone moiety ( x 256 nm, v 2850, 1770, 1643, and 1250 c n r ) , isolated from the contiguous proton systems, i s positioned on the D ring on the basis of biogenetic considerations of this class of steroids. The unusually low chemical s h i f t of the equatorial proton signal (2.70 ppm) at C-7 i s due to deshieldino by a through space e f f e c t of the methoxy group. Abyssinin (I) i s unstable i n a protic solvent such as ethanol, and epimerizes at C-17 to give a mixture of I and 17-epiabyssinin (X) (3:2). A s i g n i f i c a n t low f i e l d s h i f t U+0.41 ppm) of the C-13 CH3 signal in X vs I c l e a r l y shows that the configuration of the α-pyrone ring i s a. 17-Epiabyssinin (X) was also i s o l a t e d , and i t also epimerized to give an equilibrium mixture of X and I (2:3) i n ethanol. It i s presumable that X i s an a r t i f a c t . The aldehyde group and the acetate group must be located on the remaining quaternary carbons, C-10(51.3 ppm) and C-4(80.2 ppm) respectively. The addition of Eu(fod)3 to the CDCI3 solution spread out the congested spectrum, and induced large changes of i n the absorption due to proton 4-H. Since these s h i f t s showed complexation of the lanthanide reagent with the acetate oxygen, the configuration of the epoxide was established as a. max

m a x

1



12.

KUBO AND MATSUMOTO

191

Insect Antifeedants

F i g u r e 6.

Contour

plot.




F i g u r e 7.

Two-dimensional COSY spectrum.



12.

193

Insect Antifeedants

KUBO AND MATSUMOTO

The absolute configuration of abyssinin (I) was determined from CD studies of the tetrahydroabyssinin (IX) and i t s 3,4-bis ( £ - J M - d i m e t h y l a m i n o b e n z o a t e ) (XIII). Acid catalyzed epoxyhydrolysis of abyssinin (I) (7N H2SO4/THF, 5 0 ° C ) , followed by h y d r o g é n a t i o n (5 Pd/C., EtOH) afforded the tetrahydroglycol (XI) and i t s C-17 epimer (XII). In general, £ - N , N - d i m e t h y l a m i n o benzoates are prepared from by £ - N ^ , h [ - d i m e t T i y T a m i n o b e n z o y l chloride i n pyridine. Because the preparation and storage of t h i s reagent i s troublesome due to i t s r e a c t i v i t y with water, we prepared the more stable reagent £ - J Y , N - d i m e t h y l a m i n o b e n z o y l n i t r i l e , which reacts e a s i l y with most alcohols but not water (9). A solution o f p-N,N-dimethylaminobenzoyl n i t r i l e i n dry CH3CN was added to a UKJCTT solution o f tetrahydroglycol (XI), containing a c a t a l y t i c amount of quinuclidine and s t i r r e d a t room temperature f o r 17 h r . 3 , 4 - B i s ( £ - ] M - d i m e t h y l a m i n o b e n z o a t e ) (XIII) was p u r i f i e d d i r e c t l y from the reaction mixture by preparative TLC. The configuration of (XIII) was assigned by the *H NMR coupling constant (J=10 Hz) of the protons on carbon 3 and 4 (see Figure 8 ) . The negative f i r s t Cotton e f f e c t at 324.8 nm (Δε-38.4) i n Figure 8 showed the absolute stereochemistry o f abyssinin to be that as indicated i n structure ( I ) . This also establishes the absolute configuration of the bufadienolides that were isolated from the same source as antitumor agents: bersaldegenin 3-acetate (V), bersaldegenin 1,3,5-orthoacetate (VI), hellebrigenin 3-acetate (VII), and hellebrigenin 3,5-diacetate (VIII). Structure of Abyssinol A, B, and C The structures of these antifeedants were established mainly through the comparison o f t h e i r spectroscopic data with those of abyssinin ( I ) . *H NMR data (400 MHz) of these bufadienolides, summarized i n Table I, showed the c h a r a c t e r i s t i c signals of an α-pyrone ring and of a proton adjacent to an unsaturated carbonyl l i k e abyssinin. The signals (0.86-0.99 ppm) o f t h e i r C-13 methyl group suggest a β pyrone ring i n a l l three compounds, i n contrast to the chemical s h i f t o f the C-13 methyl group i n 17-epiabyssinin (1.34 ppm). Abyssinol A (II), m.p. 1 4 6 ° C (amorphous) has the following physical constants: IBEI-MS m/z 410(M ), 392(M -H 0), 364, 346 and 336, DCI-MS(NH ) 428Tl^ NH ) and 411(M +H), IR(CHC1 ) 3530, 2860, 1745, 1720, 1700, 1638, 1610, 1535, 1450, 1375 and 1305 c i r r i , UV(EtOH) 227U 12000) and 292U 7700) nm. The *H NMR of II i s quite s i m i l a r to that of abyssinin, except f o r the following: ( i ) the lack of the acetoxy methyl s i g n a l , ( i i ) the presence of a hydroxyl proton s i g n a l , ( i i i ) the lack of the methoxy methyl signal and (iv) the presence of an o l e f i n i c proton signal at 5.92 ppm. Together with the Ε Ι - M S data, ( i ) and ( i i ) indicate that δ β - a c e t o x y l group i n abyssinin should be replaced by a δ β - h y d r o x y l group, which i s also supported by the change i n the s h i f t ( Δ - . 4 1 ppm) of the proton attached to C-4. A molecular model of abyssinin shows that the C-4 proton i s close enough to the acetoxy-carbonyl group as to be subject to an a n i s o t r o p i c deshielding, although t h i s i s n ' t possible i n the case of II. Since the 5.92 ppm o l e f i n i c proton o f II i s coupled to the +

3

+

4

+

2

+

3




194



Me

OMe OAc

H-23

H-22

H-21

H-15 H-17 H-19

H-8

H-4

H-3

H-2

H-l

0.99(3H,s)

7.30(lH,brd,2.5) 7.02(lH,dd,9.5, 2.5) 6.32(lH,dd,9.6, 1.1)

3.05(lH,dddd, 11.7,11.7,2.9,1.8 5.92(lH,d,1.8) 3.14(lH,s) 9.83(lH,d,1.8)

3.53(lH,m) 3.08(lH,d,3.7)

Abyssinol A

0.91(3H,s)

3.83(3H,s)

3.59(lH,d,12), 3.33(lH,d,12) 7.29(lH,d,2.7) 7.04(lH,dd,9.6, 2.7) 6.32(lH,d,9.6)

2.98(lH,s)

4.23(lH,d,J=11.5,0H) 3.25(lH,brs.0H) 3.56(lH,m) 3.09(lH,d,3.6)

Abyssinol Β

3.84(3H,s) 2.06(3H,s), 2.05(3H,s) 0.86(3H,s)

7.29(lH,d,2.6) 7.02(lH,dd,9.5, 2.6) 6.32(lH,d,9.5)

10.18(lH,s)

2.96(lH,s)

0.93(3H,s)

3.85(3H,s) 2.03(3H,s)

7.30(lH,d,2.5) 7.04(lH,dd,9.8, 2.5) 6.33(lH,d,9.8)

9.84(lH,s)

3.00(lH,s)

3.03(lH,ddd,10,10,4)

2.20(lH,ddd,12,6,3), 1.69(lH,ddd,12,ll,2) 3.43(lH,m) 3.49(lH,d,3)

2.31(lH,m), 1.80(lH,m) 5.31(lH,m) 2.36(lH,dd,4,16.1) 1.92(lH,dd,2,16.1) s

1.73(lH,m),1.93(lH,m)

Abyssinin

5.76(lH,m,Wj=5)

Τ

Abyssinol C

H NMR spectral data of abyssinol Α . Β and C and abyssinin in CDCI3.

l

Assignment

Table 1.


196


isolated a l l y l i c 8-H a t 3.05 ppm (1.8 Hz), t h i s o l e f i n i c proton was placed a t C-15 to replace the methoxy group found i n abyssinin. The UY spectral data are consistent with t h i s . Abyssinol Β ( I I I ) , Ε I - M S m/z 442(M ), 424(M -H 0), 406(M -2H 0), 394 and 287, UV(ItUH) 220(ε 9700), 253 (ε 14300) and 290(ε 7200, sh. ) nm, contains two hydroxyl groups. One was placed a t C-5 f o r the same reason as i n the case of abyssinol A . The other was assigned to C-19 since the *H NMR signal due to the aldehyde group i n abyssinin was not observed i n abyssinol B, but was replaced by a new isolated AB system corresponding to -CH 0H appearing at 3.59 and 3.33 ppm (J=12 Hz). Thus, abyssinol Β was determined to be structure III. Abyssinol C (IV), m.p. 1 5 4 ° C (amorphous), Ε Ι - M S m/z 542(M ), 524(M -H 0), 482(M -CH C00H), 464, 422(M -2CH C00H), 404, 376 and 286, UV(EtOH) 225(ε 7900, s h . ) , 253(ε 13400) and 290(ε 6600, sh.) nm, d i f f e r e d from abyssinin i n the following respects: ( i ) the C-5 acetoxyl group i s replaced by hydroxyl group as i n the case o f abyssinol A and B, ( i i ) two secondary acetoxyl groups (2.06 and 2.05 ppm) are present i n r i n g - Α instead o f the epoxy group found i n Abyssinin. Since the coupling values of the acetate bearing methine protons (5.76 and 5.31 ppm) are consistent with the expected values for equatorial protons, the stereo chemistry o f the two acetoxyl groups were assigned as a x i a l . Further, a 1,3-diaxial relationship was disclosed by double resonance experiments. Of the two possible structures (1,3-diaxial structure XIV o r XV i n ring A ) , XIV was chosen because the aldehyde proton signal underwent a low f i e l d s h i f t (ΔΟ+0.34 ppm) compared with that o f abyssinin. The structure of abyssinol C was therefore established as shown i n IV. +

+

+

2

2

2

+


+

2

Antifeedant

+

3

+

3

Activity

Abyssinin ( I ) , 17-epiabyssinin (X), abyssinol A ( I I ) , Β ( I I I ) , C (IV) and abyssinin derivatives (IX and XVI) were tested f o r antifeedant a c t i v i t y i n a 'choice' situation (10). Leaf disks (1 cm ) were punched out from a glandless cotton c u l t i v a r (Pima S-4 of Gossypium barbadanse, a favored host o f the cotton budworm H e l i o t h i s zea), randomized, and arranged on moistened f i l t e r paper i n polyethylene form grids inside glass p e t r i dishes as shown i n Figure 9. Alternating disks were treated with e i t h e r 25 μΐ acetone or with from 1 ug to 100 \xg o f t e s t compounds dissolved i n 25 μΐ acetone. Three newly-molted t h i r d i n s t a r larvae of the cotton budworm were then placed i n the disks a t 2 2 ° C and 80 RH i n a dark incubator. After 48 h r s , the larvae were removed and the disks were v i s u a l l y examined. Table II indicates a PC95 of ( I ) - ( I V ) , (IX), (X) and (XVI) f o r IH. zea larvae. PCg§ values are concentrations o f samples resulting i n 95 protection" o f treated disks when compared to untreated d i s k s . Cotton leaf disks which had been treated with 5 \ig o f abyssinin (I) o r 17-epiabyssinin (X) were not eaten by H. zea. 2


KUBO AND MATSUMOTO

197

Insect Antifeedants


12.

Figure

9.

Cotton

leaf

disk "choice"

bioassay.





12.

KUBO AND MATSUMOTO Table II.

199

Antifeedant a c t i v i t i e s (PC95) of bufadienolides against H. zea.

Compounds

(I) (X) (II) (III) (IV) (IX) (XVI) Downloaded by UNIV OF ROCHESTER on June 24, 2013 | http://pubs.acs.org Publication Date: April 26, 1985 | doi: 10.1021/bk-1985-0276.ch012

Insect Antifeedants

PC95wg/disk)

5 5 25 20 20 >100 >100

Abyssinol A (II), Β (III) and C (IV), without the acetoxyl moiety, were less active than abyssinin (I) and 17-epiabyssinin (X) with the acetoxyl moiety. We had observed a s i m i l a r decrease of antifeedant a c t i v i t y due to the removal of the acetoxyl group when we investigated antifeedant a c t i v i t i e s o f the ajugarins (11). Tetrahydroabyssinin (IX) and i t s epoxy-hydrolyzed derivative (XVI) were found to be inactive even at 100 ug/disk. This suggests both the α-pyrone ring and the epoxide group are required f o r the strong antifeedant a c t i v i t y of abyssinin (I). We also conducted a 'no-choice a r t i f i c i a l d i e t feeding assay (12), since compounds not showing antifeedant a c t i v i t y but having growth inhibitory a c t i v i t y would be overlooked i n the previous 'choice' s i t u a t i o n . As a r e s u l t , we isolated only abyssinin as an insect growth i n h i b i t o r while monitoring by an a r t i f i c i a l d i e t feeding assay. In f a c t , abyssinol A (II), Β (III) and C (IV), isolated monitoring by the l e a f disk assay, d i d not show any insect growth inhibitory a c t i v i t y , as i s shown i n Table III. 1

Table III.

Growth inhibitory a c t i v i t y (ED50 i n ppm) of bufadienolides against Pectinophora g o s s y p i e l l a .

Compounds

EDso(ppm)

(I)

10

(ID

>50

(III)

>100

(IV)

>100

(IX)

>150

(XVI)

>150

G a l l i c acid

>500

Methyl

>500

gallate


200

BO IREGULATORS FOR PEST CONTROL

Thus, the growth inhibitory a c t i v i t y of abyssinin (I) compared to abyssinols (II-IY) could be attributed to a 'potent' antifeedant e f f e c t which can cause starvation. Accordingly, the antifeedant a c t i v i t i e s of the abyssinols (II-IY) appear not to be strong enough as to force starvation. G a l l i c acid and methyl gal l a t e , isolated monitoring by antimicrobial a c t i v i t y against subtil i s , were inactive against P. gossypiella even a t a concentration of 500 ppm. On the other Fana, abyssinin (I) did not show microbial a c t i v i t y against EL subtil i s even at a high concentration. This shows another example where d i f f e r e n t type of secondary compounds a c t i n a variety of ways as defense adaptations of a plant.


Acknowledgments Insects f o r the bioassay were kindly supplied by the agencies of the USDA i n Phoenix, AZ; T i f t o n , GA; and Brownsville, TX. The authors are grateful to Dr. H. Naoki and Professor A. S . Kende f o r NMR measurements, Professor N. Harada f o r CD measurement, and Dr. J . A. Klocke f o r antifeedant bioassay. Literature

Cited

1.

J. O. Kokwaro, "Medicinal Plants of East Africa"; East African Literature Bureau, Nairobi, 1976; p. 159. 2. I. Kubo and K. Nakanishi, "Host Plant Resistance to Pests"; ed. by P. A. Hedin, ACS Symposium Series 62, American Chemical Society: Washington, D.C., 1977; pp. 165-178. 3. S. M. Kupchan and I. Ognyanov, Tetrahedron Lett., 1709 (1969), S. M. Kupchan, R. J. Hemingway and J. C. Hemingway, J. Org. Chem., 34, 3894 (1969). 4. P. Zanno, I. Miura, K. Nakanishi and D. Elder, J. Am. Chem. Soc., 97, 1975 (1975). 5. P. J. May, Terpenoidas and Steroids, 1, 527 (1971). 6. L. Gsell and Ch. Tamm, Helv. Chim. Acta., 52, 551 (1969). 7. K. Nakanishi, T. Goto, S. Ito, S. Natori and S. Nozoe, "Natural Products Chemistry"; Academic Press: New York, 1974; p. 469-476. 8. J. Meinwald, D. F. Wiemer and T. Eisner, J. Am. Chem. Soc., 101, 3055 (1979). 9. J. Goto, N. Goto, F. Shamsa, M. Sato, S. Komatsu, K. Suzaki and T. Nambara, Anal. Chim. Acta., 147, 397 (1983). 10. I. Kubo and J. A. Klocke, l'Colloques de l'I.N.R.A., 7, 117 (1981). 11. B. G. Chan, A. C. Waiss, Jr., W. L. Stanley and A. E. Goodban, J. Econ. Ent., 71, 366 (1978). RECEIVED

November 8, 1984


Potent Insect Antifeedants from the African Medicinal Plant - American

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