IS0LATI 0N OF M ETHY 1,C:ISS I NE FROM SPECIES O F THE GENUS PROSOPIS I . B. GIINI~ETTO, J. L C ~ B R Eand R ~H . R . J U L I ~ S I Facultad de Caencaas Qmniicas, Departameiifo dP Farmacia, Chfedra de Farmacognosia, Cnziterszdad 'Yacional de Cdrdoba, Estafefa 32, 5000 CORDOBA, Repiiblzca Argentina
Previous phytochemical studies of the genus Prosopis (Leguminosae) have demonstrated that several species contain a number of known flavonoids (1-3) as Tyell as alkaloids (4-10). I n this paper we wizl t o report the isolation and structural determination of S-methyleassine (1) from the bark of Prosopis iiigra (Griseb.) Hieron., P.ruscifolia Griseb. and P. titzalillo Stuck. This is the first report of the isolation of this compound from a natural source, although it has been previously synthesized from cassine by Highet (11).
The identification of (1) was confirmed by comparison of the physical properties with those of the authentic compound which was prepared from cassine according t o the literature (11). A portion of S-methylcassine was converted in the hydrochloric derivative by treatment with 57, methanolichydrochloric acid solution, evaporated to dryness and recrystallized from absolute ethanol. The mp observed n-as 109-110" (lit. (11): 110.5-111.5").
EXPERIJIESTAL' PLA\T
\I ~ T E R ~ I L . - P . nzgra (Griseb. ) Hieron. and P. rusczfolza Griseb. were identified by Prof. Ing. ,4gr. -4.T. Huntziker. Toucher specimens are on deposit in hluseo BotAnico, Univ. Nac. de C6rdoba. P . eznalzllo Stuck. was identified by Dra. Beatriz Soraru. a voucher specimen is on deposit in the Herbariun of the Departamento de Farmacognosia y Fitoqfiimica Fac. de Farmacia y Bioquimica, Univ. Nacional de Buenos Aires. Plant material was collected in Santiago del Estero (Repitblica Argentina). The bark was air dried and powdered. EXTR~CTIOZT ~ S D PcRIFIc.~TIOx.-The extraction method was identical for all the three species. Powdered bark (400 g) was extracted with methanol for 48 h a t room temperature. After elimination of the solvent a t reduced pressure, the total residue was suspended in 200 ml of 5% hydrochloric acid, stirred mechanically and filtered. The acidic extract containing the alkaloids R-as adjusted t o pH 8 Kith ammonia and extracted Kith petroleum ether in a liquidliquid extractor until no Dragendorf reaction was observed in the aqueous layer.
H3C HoQrCW,;,,cocH3 CH3 1
The crude alkaloid extracts obtained from all the species, when purified by preparative tlc, yielded Smethylcassine. The mass spectrum showed the molecular ion a t d e 311 (0.79%) (Ci9H3iiYOn) and the base peak a t 128 (100%) due to the loss of the aliphatic side chain. Other identified peaks indicated the elimination of the COCH, moiety and a number of signals, separated 14 m.u. each, corresponding to the degradation of the side chain. This pattern of fragnientation is coincident n-it11 that previously reported for this type of alkaloid (8). The nmr spectrum was almost identical with that of cassine, except for a singlet a t 6 2.28 (3H) attributed to the methyl attached to the nitrogen.
'Smr spectra n-ere carried out on a Tarian T-60 instrument in DCC13 with tms as internal standard, ms spectra in a 1-arian MAT C H i a t io eT-: ir spectra in a Beckman I R 8 instrument in KBr ,disc. The melting points were determined in a Koffler apparatus and are uncorrected. Silica gel G mas used for tlc. The solvent systems and I),f were, respectively: A)ir-butanol-acetic acid-water (4:1:2) (0.58) and chloroformmethanol-ammonia ( 9 3 . i : O 1) (0.10).
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GIASIXETTO ET AL.
The organic solvent was then removed iu ;'iicuo. The alkaloid residue shoR-ed several spots on tlc. The spot a t Rf 0.10 (Syst. B) corresponded to .\*-methyleassine. The alkaloid was obtained pure h>-preparative tlc t . B ) : the zone a t lif 0.10 v-as removed from the tlc plate and eluted with methanol, and the solvent x a s then removed i,i c'acuo. This m-as repeated several times t o obtain pure material. A\--niethylcassine thus obtained showed identical chromatographic properties with those of the synthetic alkaloid prepared from cassine (111 . Both ir spect ra x e r e superimposahle. .iCKSOWLEDGlIESTP The ailthors thank Prof. I n g . I g r . A. T. Hiinziker and Prof. Dra. Beatriz Sorani for the identification of specimens and Prof. Dr. E. G . Gros, Faciiltad de Ciencias Esactas y Saturales, Vniv. Sacional de Buenos -lires>for the mass spectrum. Recei;,ed 18 December 1979. LITERATURE C I T E D 1. I. B. Gianinetto. J . L. Cabrera. J. C.
Oberti and H. 265 (1975).
G.Juliani,
L l o ~ d ? a38, ,
S-3IETHTLC.ISSISE
2.
633
I . B. Gianinetto, R . -1.Giollo and H . R . .Juliani, Phyfocheniisiry, 16, 2027 (1976).
I . B. Gianinetto, J. L. Cabrera, J . C. Oberti and H. R . .Juliani., Phl'iGG/iel?:; ~ t r y 15, , 1695 (1976). 4. G . Moro, AI. S . Graziano and J . D. Coussio, Plryfocireniisfry, . . 14,2945 (1966). 5 . G. Rattle, X . RIonseur, D. C . Dns, .J. l a s s i , 9. Kuong-Huu et R. Goutarel, Biill. Soc. Chiii:. F r a n c e , 9, 2945 (19fi6). 6. .J. L . Parente, J. .i. Herrera, .J. C. Oberti >- H . R . .Juliani, di:ii!es d s o c . Q i l i w . -4rge,ifinn! 60, 527 (1972). (1. Khuong-Huu, G. Ratle, 1.Monseur et R . Goutarel, Biill. Soc. Chin?.Beiges, 3.
81, 425 (1972:.
8. Q. Khuong-Huu, G . Ratle, X. Nonseur et R.Gontarel, Bull. SOC.Chim. Belges, 81, 443 (1972). K . Jewers, H. J . Kagler, K. -i.Zirvi , 238 and F. .imur, P l i y f ~ c i : e m i s f r y15, (1976). 10. I-. U. .ihmad, -4.Basha and I-.Haque, 2. S a t z t r f o r s c h . , 33, 347 (19;6). 11. R. J . Highet, J . Org. Cheni., 29, 471 (1964). 9.
