~hyroclkcmirny. Vol. 25. No. 7. pp. 1779-1780. 1986. 003 I -9422/86 f3.00 + 0.00 Printed in GIUII Britain. Paxamon Jounuta Ltd.

1,2-DEHYDROASPIDOSPERMIDINE-N-OXIDE, AN ALKALOID FROM RHAZl5l STRICTA

ATT+UR-RAHMAN* and KHUBSHID ZAMAN

H.EJ. Research Institute of Chemistry, University of Karachi, Karachi-32, Pakistan

(Rcdsd raxid 24 Sept& 1985)

Key Word l&x-Rhasyo stricta; Apcqwaac, . alkaloid$ 1,2dehydroaspid~idine-N-oxide; FAR-MS.

Abstract-A new alkaloid, 1,2dehydroaspidospermidine-N-oxide, has been isolated from the roots of Rhazyo stricta.

tNTBODUCllON

Rhuzya stricta (Apocyaaceae) is a medicinal plant found in several regions of Pakistan. The plant is reputed in the indigenous system of medicine to be a cure for boils, eruptions, sore throat [l-3; Raquar, S. R.. unpublished], syphilis [l, 2.41, a bitter tonic for fever [l-3; Raquar, S. R., unpublished] and for chronic rheumatism [S, 63. The leaves have anticancer properties [S, 6; Raquar, S. R., unpublished]. We have previously reported a number of new alkaloids from the plant [7-l 11. In continuation of our studies on the isolation and structure elucidation of new chemical constituents from the roots of R. shicta, we have isolated a new alkaloid which has been shown to be the Naxidc of 1.2dehydroaspidospermidine (1).

RESULTS AND DIBCUBBlON

The crude alkaloids were obtained from the ethanolic extract of the roots by the conventional procedures [ 111. The crude extract was fractionated by extraction into chloroform at different pH values The new alkaloid was obtained from the extract at pH 8 by repeated chromato- graphic purification on silica gel GF-254, [a]o + 120” (CHClz). The substance gave a UV spectrum character- istic of the indolenine system, showing absorption maxima at 206, 222, 26Onm and minima at 217 and 245nm The IR spectrum showed a peak at 17lOcm-’ and minima at 2 17 and 245 nm. The IR spectrum showed a peak at 171Ocm- * indicating the presence of a C=N group. The substance afforded a mass spectrum with a strong peak at m/z 280.1434 and a very small [M] l peak at m/z 2% (CIPHz4N20). The exact mass of the molecule could be obtained by fast atom bombardment mass spectrometry which showed a [M + H] l peak at m/z 297.1927 (C,9H,,N,0 requires 297.1967). Exact mass measurement with an EI source gave the mass of the molecular ion to be 296.1849 in agreement with the formula CIPHz.NzO. Other signiticant peaks (by EI) wereatm/z280[M -0]‘,251[280-CzHs]*.210,194, 169,168,156,149,125.97,83 and 56. The fragmentation pattern was remarkably similar to that reported for 1,2-

*Author to whom eorrespondenee shot&l be addressed.

dchydroaspidospermidine suggesting that the substance was the corresponding N-oxide.

The ‘H NMR spectrum of 1 (300 MHz) showed the presence of a tripkt at 60.49 (I = 7.5 Hz) which is assigned to the methyl protons of the ethyl chain The methylene protons of tbc ethyl group resonated as a quartet at 61.71 (J = 7 Hx). A sharp singlet at 63.74 is assigned to the C-19 proton. The downfield position of this signal as compared to its usual position in aspidosperma alkaloids [ 121 is consistent with the pre- sence of a quatemary adjacent nitrogen The aromatic protons resonated as compkx multiplets in the range of 67.13-7.52

Attempted deoxygenation by reduction with NaR& in methanol, or by treatment with Xl, 1133. led to the formation of an indolic compound which showed an [Ml’ peak at m/z 298 and other fragment peaks at m/z 297,251,225, 197, 170. 169.124 and 97. The structure of this product is presently under investigation.

On the basis of the above spectral studies the new alkaloid is identified as 1,2dehydroaspidospermidine-N- oxide.

EXPERIMENTAL

FABMS were measured in glycerol-H,0 (1: 1) in the prcseoa of KI. Accurate mass measuremen t with the FAR source were made using ~tyccrol as int standard. ‘H NMR spaxra were recorded in CLXl, at 300 MHq UV in MeOH and IR in CHCI,.

Isolarion of 1. Roots (75 kg) of R stricra Daxisnc wcreaushad withanUltra_TurraxinEtOH(120L).fhenrr~~filtcrcd and evapd under vacuum to a gummy mass (9OOg). The gum was

1779

I780 Short Reports

acidified with 10% HOAc to pH 3 and extracted with CHCl, (2 I.). The aq. layer was bar&d with NH, to pH 14 and washed with CHCI, (2 1) and EtOAc (2 1). The organic extracts were com- bined, dried (Na&O& 6ltcred, cvepd and treated with 2 % aq. tartar& acid (31) and then extracted with CHCI, (1.51) at different pH valued. The extract at pH 8 was dried (Na,SO,), filtcndaDdconodtoaaudcalkabidPlgum(7.Sg).~8umwas then subjected to repeated prep. TLC which aRo&d a pure compound (IO mg) in hexareMe,CO (7:3)+NH, (5 dropsk [aID 120” (CHCI,); UV McOH & nm: 206,222.,260. & mn: 217,245; IRvT: l7lOan- ‘; ‘H NMR (CDCl,) 60.49 (3H, r, Il,.zo = 7.0 H.G CHa-b&), 1.71 (2H, q, IzQ,~~ = 7.0 Hq C&- Me), 3.74 (IH, s, H-19), 7.137.52 (4H, m, aromatic protons); MS m/z (rel int.): 296 [Ml+ (I), 2JJO (46), 251 (23), 210 (37), 194 (2l), 169 (9), 168 (12). 156 (IZ), 149 (33X 125 (32), 97 (42), 83 (48X 56 (lOo).Peakmatchingmc;rs urcmcnts (EI): 296.1849 (C,,HUN~O, requires 296.1888), ml934 (C,,H~NI, requires 280.1939); FAB: 297.1927 (C,&,NIO, requires 297.1967).

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