2694
K.M. Meepagala et al. / Phytochemistry 66 (2005) 2689–2695
2000; Meepagala et al., 2002; Oliva et al., 2003). In order to
evaluate the quantitative fungicidal activity, the active
compounds were evaluated in a 6-point dose–response for-
mat in the 96-well micro-bioassay using modifications to
published methods (Wedge et al., 2000; Meepagala et al.,
2002; Oliva et al., 2003). Rutacridone epoxide (1) was eval-
uated at six concentrations (0.0625, 0.125, 0.25, 0.50, 1.0,
and 2.0 lM) in comparison to the commercial fungicides
captan (multisite inhibitor) and benomyl (b tubulin inhibi-
tor) for activity against C. fragariae, C. gloeosporioides, C.
acutatum, and Botrytis cinerea and Fusarium oxysporium.
elusions) to give methyl-20(R),30(S)-40-epoxytubaiate (12)
and methyl-20(R),30(R)-40-epoxytubaiate (11).
3.11.4.1. Methyl 20(R),30(S),4-epoxytubaiate (12). White
23
solid m.p. 136–137 ꢀC; ½aꢁD ꢀ51.2ꢀ; HRESI-MS: 234.0894
1
(calc. for C13H14O4, 234.0892), H NMR d (CDCl3) 1.43
(3H, s, 50-CH3), 2.73 and 2.84 (2H, d, J = 4.8 Hz, 40-Ha,
Hb), 3.09 (1H, dd, J = 16.0, 8.0 Hz, 10-H), 3.25 (1H, dd,
J = 16.0, 10.0 Hz, 10-H), 3.92 (3H, s, –OCH3), 4.83 (1H,
dd, J = 10.0, 8.0 Hz, 20-H), 6.38 (1H, d, J = 8.4 Hz, 5-H),
7.70 (1H, d, J = 8.4 Hz, 4-H).
3.10. Bioassay for phytotoxic activity
3.11.4.2. Methyl 20(R)-30(R), 40-epoxytubaiate (11). White
23
solid m.p. 121–122 ꢀC; ½aꢁD ꢀ47ꢀ (CHCl3; 0.40), HRESI-
The compounds were evaluated for phytotoxicity on
monocots and dicots using lettuce and bentgrass seeds
according to published methods (Dayan et al., 2000). Phy-
totoxic activities were ranked in a scale from 5 to 1 visually
with 5 being complete inhibition of germination and 1
being no inhibition.
MS: 234.0893 (calc. for C13H14O4, 234.0892), 1H NMR d
(CDCl3) 1.39 (3H, s, 50-CH3), 2.70 and 2.93 (2H, d,
J = 4.8 Hz, 40-Ha, Hb), 3.11 (1H, dd, J = 16.0, 7.6 Hz, 10-
H), 3.31 (1H, dd, J = 16.0, 10.0 Hz, 10-H), 3.91 (3H, s, –
OCH3), 4.76 (1H, dd, J = 10.0, 7.6 Hz, 20-H), 6.37 (1H, d,
J = 8.6 Hz, 5-H), 7.70 (1H, d, J = 8.6 Hz, 4-H).
3.11. Syntheses
References
3.11.1. Rotenone epoxides (9,10)
Aliotta, G., Cafiero, G., De Feo, V., Sacchi, R., 1994. Potential
allelochemicals from Ruta graveolens L. and their action on radish
seeds. Journal of Chemical Ecology 20, 2761–2775.
Aliotta, G., Cafiero, G., De Feo, V., Di Blasio, B., Iacovino, R., Oliva, A.,
2000. Allelochemicals from rue (Ruta graveolens L.) and olive (Olea
europaea L.) oil mill waste waters as potential natural pesticides.
Current Topics in Phytochemistry 3, 167–177.
Baumert, A., Groeger, D., Schmidt, J., Muegge, C., 1987. Minor alkaloids
from Ruta graveolens tissue cultures. Pharmazie 42, 67–68.
Baumert, A., Maier, W., Schumann, B., Groeger, D., 1991. Increased
accumulation of acridone alkaloids by cell suspension cultures of Ruta
graveolens in response to elicitors. Journal of Plant Physiology 139,
224–228.
Bergenthal, D., Mester, I., Rozsa, Z., Reisch, J., 1979. Studies in the field
of natural product chemistry. Part 63. Carbon-13 NMR spectra of
acridone alkaloids. Phytochemistry 18 (1), 161–163.
Dayan, F.E., Romagni, J.G., Duke, S.O., 2000. Investigating the mode of
action of natural phytotoxins. Journal of Chemical Ecology 26 (9),
2079–2094.
De Feo, V., De Simone, F., Senatore, F., 2002. Potential allelochemicals
from the essential oil of Ruta graveolens. Phytochemistry 61, 573–578.
Eilert, U., Ehmke, A., Wolters, B., 1984. Elicitor-induced accumulation of
acridone alkaloid epoxides in Ruta graveolens suspension cultures.
Planta Medica 50 (6), 508–512.
Habib, A.M., Ho, D.K., Masuda, S., McCloud, T., Reddy, K.S.,
Aboushoer, M., McKenzie, A., Byrn, S.R., Chang, C.J., Cassady,
J.M., 1987. Structure and stereochemistry of psorospermin and related
cytotoxic dihydrofuranoxanthones from Psorospermum febrifugum.
Journal of Organic Chemistry 52 (3), 412–418.
Haller, H.L., Laforge, F.B., 1930. Rotenone. VII. The structure of tubanol
and tubaic acid. Journal of the American Chemical Society 52, 3207–
3212.
Epoxide of rotenone was prepared by adding m-chlor-
operbenzoic acid (17.3 g, 0.1 mol) in 50 mL CHCl3 drop
wise into a solution of (7) (19.72 g, 0.05 mol) in 100 mL
CHCl3 according to the published method (Habib et al.,
1987). The product was purified by silica gel column chro-
matography using EtoAC in hexane to afford a mixture of
diastereomeric epoxides as a white powder, which was sep-
arated by PTLC using hexane and EtoAC (80:20) as the
solvent (5 elusions).
3.11.2. (ꢀ)-Tubaic acid (13)
(ꢀ)-Tubaic acid was prepared by alkaline degradation
of commercially available (ꢀ) rotenone with 10% KOH
in MeOH as described by Haller and Laforge (1930).
The identity was confirmed by comparison of NMR
spectroscopic data with those published in the literature
(Obara et al., 1976). CD (c = 2.3 · 10ꢀ4
, CHCl3):
[h]262ꢀ9.7 · 103, [h]275ꢀ1.1 · 104.
3.11.3. Methyl tubaiate (8)
(ꢀ)-Tubaic acid was dissolved in MeOH and treated
with ethereal diazomethane at 0 ꢀC. Solvent was removed
under vacuum and the product was crystallized from
MeOH to give pale yellow crystals (Obara et al., 1976).
3.11.4. Epoxydation of methyl tubaiate
A mixture of methyl tubaiate (100 mg) and m-chloroper-
benzoic acid (150 mg) in CHCl3 (5 ml) was stirred at room
temperature for 24 h. The reaction mixture was diluted
with CHCl3 and washed with aqueous sodium carbonate,
water dried over magnesium sulfate and evaporated to give
a mixture of diastereomeric epoxide. This mixture was sep-
arated by preparative TLC using hexanes:EtoAc 90:10 (3
Ho, D.K., McKenzie, A.T., Byrn, S.R., Cassady, J.M., 1987. O5-Methyl-
(
)-(20R,30S)-psorospermin. Journal of Organic Chemistry 52 (3),
342–347.
Kawaii, S., Tomono, Y., Katase, E., Ogawa, K., Yano, M., Takemura, Y.,
Ju-ichi, M., Ito, C., Furukawa, H., 1999a. Acridones as inducers of HL-
60 cell differentiation. Leukemia Research 23 (3), 263–269.
Kawaii, S., Tomono, Y., Katase, E., Ogawa, K., Yano, M., Takemura, Y.,
Ju-ichi, M., Ito, C., Furukawa, H., 1999b. The antiproliferative effect