Tropane alkaloids from a Brazilian bark traded as "Catuaba" *

Dichloromethane extracts of a Brazilian bark assigned as Anemopaegma mirandum contained four tropane alkaloids. MS-, UV-, IR-, 'H NMR-data and spe-cific optical rotation allowed the identification of catuabin C and its 7-exo-hydroxy-20-methyl-derivative. As no alkaloids are described for Anemopaegma these results indicate heterogeneity for the investigated drug and require a further review.


Introduction
The Brazilian bark Catuaba is known as tonic, stimulant and aphrodisiac. Its long tradition in folk medicine and the increasing popularity in Europe raise the question concerning the active compounds. One Brazilian product assigned as Anemopaegma mirandum (Bignoniaceae) was screened for characteristic constituents [I]. A positive reaction with Dragendorff reagent indicated alkaloids [2], four of them were isolated, two of the isolated alkaloids were structurally elucidated by HPLC-UV, I D and 2D-NMR, MS and IR [3].
Presented at the 5om Annual Congress of the Society for Medicinal Plant Research, Barcelona, Sept. 8

HPLC
Analyses were performed on a Merck Hitachi liquid chromatograph consisting of a Rheodyne injection unit, a L-7100 pump, a L-7450 diode array detector (monitoring wavelength: 270nm) and a D-7000 interface. Computations were performed using the Merck D-7000 HSM software. Stationary phase: ~i~h r o s~h e r @ 1 0 0 -~~8 5pm (4x250mm); mobile phase: methanol-water, start from 20% up to 80% methanol in 90 minutes, rate: O,G%/min, flow: Iml/min; UV spectra were recorded on-line in methanol-water by diode array detection during the HPLC runs.

Results
50g of the powdered drug were moistened with concentrated ammonia for 15 minutes and extracted four times with 70ml dichloromethane. The unified dichloromethane fractions (280ml) were extracted five times with the same volume of 2N HCI. Subsequently the unified aqueous layers were adjusted to pH 9 with ammonia and extracted six times with dichloromethane yielding crystals of an alkaloid mixture (44mg) after evaporation. CC on silica gel was performed with dichloromethanemethanol mixtures: 99+1, 98+2, 97+3, 95+5, 9+1 and 8+2. Fraction 98+2 contained a mixture of the compounds 1 and 2 which were purified by HPLC on RP8. Gradient elution with methanol-water yielded 1 .I 2mg 1 and 1.53mg 2.
On the basis of these spectral data, the structure of compound 2 was identified as catuabin C. Compound 1 was identified as 7-exo-hydroxy-20-methyl-catuabin C.
Separation of fraction 9+1 by HPLC on RP8 showed two polar alkaloids (positive reaction with Dragendorff reagent on TLC) which were characterized by their molecular weights (3 m/z=280, 4 m/z=264). The amounts were too small for NMR analyses but the fragments obtained by El-MS resembled to those of 1 and 2 indicating also alkaloids with a tropane structure (see experimental).

Conclusion
Tropane alkaloids are described for several families (Solanaceae, Erythroxylaceae, Proteaceae, Euphorbiaceae, Rhizophoraceae, Convolvulaceae, Cruciferae) [4]. Catuabin C is known for Erythroxylum vacciniifolium [5,6] and the investigation of "Erythroxylum catuaba" showed similar alkaloids [7]. However, there is no evidence for this type of compounds in Bignoniaceae. The fact that tropane alkaloids were found in a sample specified as bark of Anemopaegma miran-dum (Bignoniaceae) indicates that, additionally, a species of the genus Erythroxylum is present. This corresponds to Daly [8] and Marques [9] who report that various genera are collected and traded under the name Catuaba. The resulting identification problems are subject of a paper in preparation.