*Corresponding author. Tel.:#1-919-515-3792; fax:#1-919-515-3436.
E-mail address:[email protected] (W. Scott Chilton)
1Present address: Centro de InvestigacioHn CientmH "ca de YucataHn, Apartado Postal 87, CoHdigo Postal
97310, MeHrida, YucataHn, Mexico.
Biochemical Systematics and Ecology 28 (2000) 1019}1021
Isobutylamide numbing agents of toothache grass,
Ctenium aromaticum
Rubi Gamboa-Leon
1
, William Scott Chilton
*
Department of Botany, North Carolina State University, Raleigh, NC 27695, USA
Received 13 August 1999; accepted 21 October 1999
Keywords: Ctenium aromaticumPanz. (Poaceae); Toothache grass; Numbing agents; Pellitorine; Isoa$nin; Isobutylamides
1. Subject and source
Ctenium aromaticumPanz. (Aegilops aromaticaWalter,Monocera aromaticaElliott,
Chloris monostachyaMichaux,) is a grass restricted to wet areas of the coastal forest of the S.E. US. Knowledge of the pungent taste and numbing caused by chewing this grass dates from the 18th century or earlier (Walter, 1788; Michaux, 1805; Elliott, 1821), but use of this grass for allaying toothache was overshadowed by the more plentiful bark of toothache tree (Zanthoxylum americanum Miller, Rutaceae) in the same coastal areas of the southeastern USC. aromaticumwas collected for this study in open, long leaf pine forests near Havelock, NC and deposited in the NC State University Herbarium (Voucher no. 124425-7).
2. Previous work
No phytochemical characterization has been reported for the genusCtenium. The isobutylamide pellitorine is found widely in Asteraceae, Aristolochiaceae, Piperaceae
and Rutaceae (Greger, 1984). Isoa$nin has been reported from Achillea millefolium
(Bohlmann et al., 1974) and N-(1-isobutyl)-2,4,8,11-dodecatetraenamide has been reported once fromBrachycome ciliocarpa(both Asteraceae) (Zdero et al., 1988).
3. Present study
The pungent numbing agents ofCtenium aromaticumare present in a 1}2 cm region where roots join the base of stems and in the seed head, but not in roots or leaves. Components of methanolic soxhlet extract of the base of stems were fractionated by prep TLC (Si gel, hexane : acetone 2 : 1). Numbing activity was found in two close zones (Rf 0.70 and 0.75) detectable with phosphomolybdic acid reagent. The prep tlc fractions were further fractionated by prep HPLC (isocratic acetonitrile : water 1 : 1,
j"260 nm) to obtain three cleanly separated metabolites identi"ed as
N-(1-iso-butyl)-2(E),4(E)-decadienamide, (pellitorine, MW 223), N-(1-isobutyl)-2(E),4(E),8-de-catrieneamide (isoa$nin, M
W 221) and N-(1-isobutyl)-2(E),4(E),8,11-dodecatet-raenamide,M
W 247, by mass spectral MW and 1H-, COSY, HMBC and HMQC NMR. Spectral properties were identical to those reported for these isobutylamides (Bohlmann et al., 1974; Zdero et al., 1988). All expected proton}proton and pro-ton}carbon correlations were observed for the three compounds. Coupling constants were consistent with a trans, trans 2,4-diene system in all three amides. Chemical shifts for the isolated double bond in two of the three amides overlapped, precluding cis}trans assignment. Spectrally pure dodecadienamide caused numbing action on the gums and tongue; pure pellitorine is known to be tasteless but to produce a numbing sensation (Jacobson and Crosby, 1971). Isoa$nin was not tested.
4. Chemotaxonomic signi5cance
Although isobutylamides of unsaturated fatty acids occur widely in the dicotyle-donous families Asteraceae, Rutaceae, Piperaceae and Aristolochiaceae (Greger, 1984), there is no previous report of the occurrence of this family of pungent, numbing agents from the Monocotyledonae.
Acknowledgements
We thank Ms. Donna Wright for help in locating Ctenium aromaticum in the
"eld.
References
Bohlmann, F., Zdero, C., Suwita, A., 1974. Chem. Ber. 107, 1038.
Elliott, S., 1821. A Sketch of the Botany of South Carolina and Georgia, Vol. 1. J.R. Schenk Publisher, Charleston, SC, p. 177.
Greger, H., 1984. Planta Med. 50, 366.
Jacobson, M., Crosby, D.G., 1971. Naturally Occurring Insecticides. Marcel Dekker, New York, pp. 140}141.
Michaux, A., 1805. Flora Boreali-Americana. Levrault Frere publisher, Paris, reprint Hafner Press, New York, 1974, p. 59.
Walter, T., 1788. Flora Caroliniana. J. Fraser publisher, London, reprint Arnold Arboretum, Cambridge, MA, 1946, p. 149.
Zdero, C., Bohlmann, F., King, R.M., Lander, N.S., 1988. Phytochem. 27, 2984.
