~) Pergamon Biochemical Systematics and Ecology, Vol. 23, No. 4, pp. 451-452, 1995 Copyright © 1995 Elsevier Science Ltd

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Exudate Flavonoids of Eupatorium cannabinum

JAN F. STEVENS,* ELIZABETH T. ELEMA* and ECKHARD WOLLENWEBERt *Department of Pharmacognosy, University of Groningen, Ant. Deusinglaan 2, NL-9713 AW Groningen,

The Netherlands; tlnstitut for Botanik der Technischen Hochschu)e, Schnittspahnstrasse 3, D-64287 Darmstadt, Germany

Key Word Index--Eupator ium cannabinum; Asteraceae; leaf exudate; flavonoid agiycones; 6-O-methy)ated flavones and flavonols.

Subject and Source Eupatorium cannabinum L. was collected near Gronigen (The Netherlands) in July 1994. A voucher specimen has been deposited at the Department of Pharmacognosy of the University of Groningen.

Previous Work Flavone aglycones and flavonol glycosides from Eupatorium cannabinum L. (Elema et al., 1989).

Present Study Fresh leaves of Eupatorium cannabinum were briefly immersed in chloroform to obtain the leaf exudate. After evaporation of the leaf washings in vacuo, the residue was dissolved in boiling methanol. The mixture was kept at --18"C for 20 rain to precipitate lipophilic material and then centrifuged. The supernatant was, after concentration in vacuo, directly chromatographed over Sephadex LH-20 with methanol as the eluent. Fractions were collected and monitored with TLC. Flavonoid containing fractions of similar composition were combined and concentrated in vacuo,

Six fiavonoid aglycones (Table 1) were detected in the purified leaf washings and identified by co-TLC on silica gel and polyamide 11 with standard markers (all were available in E. Wollenweber's laboratory). Spots were visualized under UV (350 nm) before and after spraying with NaturstoffTeagenz A. Developed plates were also examined after exposure to ammonia, which allows discrimination between 3,6,4'- and 3,6,3'- trimethylation. The TLC results were confirmed by GC comparison with standards and GC-E)MS after trimethyl silylation. Electron impact mass spectra of flavonoid TMSi ethers show abundant [M-15] ÷ ions from which the number of hydroxy and methoxy groups attached to the flavonoid skeleton can be inferred (Creaser et al., 1991).

TABLE 1. FLAVONOIDS FROM THE LEAF EXUDATE OF EUPATORIUM CANNAB/NUM AND THEIR OCCURRENCE IN OTHER EUPATORIUM SPECIES

Flavonoid Trivial name Other sources Reference

scutellarein-6-methylether hispidulin E. cuneifo/ium Kupchan et al. (1969) E. rotundifolium Kupchan et al. (1969) E. semiserratum Herz et al. (1981) E. serotinum Herz et al. (1979)

scutellarein-6,4'-dimethylether pectolinarigenin E. salvia Gonzalez et al. (1990) E. semiserratum Kupchan eta/. (1969) E. serotinum Herz et al. (1979)

6-hydroxyluteolin-6-methylether eupafolin E. cuneifolium Kupchan et al. (1969) E, subhastatum Ferraro and Coussio (1973)

6-hydroxyluteolin-6,3'-dimethylether jaceosidin E. leucolepis Herz and Kulanthaivel (1982) 6-hydroxykaempferol-3,6,4"-trimethylether santin E. ligustrinum Rodriguez etal. (1974) quercetagetin-3,6,4'-trirnethylether centaureidin E. buniifolium Caula et al. (1991)

(Received 9 December 1994)

451

452 J.F. STEVENS ETAL.

Chemotaxonomic Significance Flavonoid aglycones have been reported for about 35 species of Eupatorium, but in none of the reports their localization in the plant received attention. The present study is the first report of flavonoids from the leaf exudate of a species of Eupatorium. In view of the fact that the external accumulation of flavonoid aglycones on plant surfaces and in leaf resins now is a well-known phenomenon, it is rather amazing that few authors examine leaf washings for the presence of these compounds (Wollenweber, 1989).

Of the six flavonoids we identified in the leaf exudate of E. cannabinum, only hispidulin and eupafolin were previously reported from ground aerial parts of this species (Elema et al., 1989). However, all six flavonoids have been isolated from other species of Eupatorium (cf. Table 1), indicating that 6-methoxylation of common flavones and flavonols represents the main feature of the genus' flavonoid chemistry, as is the case in many other genera of Asteraceae (Wollenweber and Valant-Vetschera, 1995).

References Caula, S, A., Villar, S. |., Martino, V. S., Coussio, J. D. and Ferraro, G. E. (1991) Rev. LaEnoamer. Qu/m. 22, 1; Creaser, C. S., Koupai-Abyazani, M, R. and Stephenson, G. R. (1991) Org. Mass Spectrom. 26, 157; Elema, E. T., Schripsema, J. and Malingr~, T. M. (1989) Pharm. Weekb/. Sc/~ Ed. 11, 161; Ferraro, G, E. and Coussio, J. D, (1973) Phytochern/stry, 12, 1825; Gonzalez, A. G., Barrere, J. B., Diaz, J. G., Rodriguez P6rez, E. M, Yanes, A. C., Rauter, R and Pozo, J. (1990) Phytochem/stry 29, 321; Herz, W., de Groote, R., Murari, R., Kumar, N. and Blount, J. F. (1979) J. Org. Chem. 44, 2784, Herz, W,, Govindan, S. V. and Kumar, N. (1981) Phytochemistry 20, 1343; Herz, W. and Kulanthaivel, R (1982) Phytochernistry 21, 2363; Kupchan, S. M., Sigel, C. W., Hemmingway, R. J., Knox, J. R. and Udayarnurthy, M. S. (1989) Tetrahedron 25, 1603; Rodriguez, J., Tello, H., Quijano, L., Kaledron, J., Gomez, F., Romo, J. and Rios, T. (1974) Rev. Lat/noamer. Quire. 5, 41 ; Wollenweber, E. (1989) Naturw/ssenschaften 76, 458; Wollenweber, E. and Valant-Vetschera, K. M. (1995) In Compos/tae. Systemadcs, B/o/ogy, Ut//izadon (C. Jeffrey, ed.). Royal Botanic Gardens.