3-EPI-austrobailignan-7: A 2,5-diaryl-3,4-dimethyltetrahydrofuranoid lignan from Aristolochia chilensis

Phytochemutry, Vol. 34, No. 3, pp. 874 875. 1993 Printed in Great Britain.

0

0031 9422/93$6.00+ 0.00 1993 Pergamon Press Ltd

3-WI-AUSTROBAILIGNAN-7: A 2,5-DIARYL-3,4_DIMETHYLTETRAHYDROFURANOID LIGNAN FROM ARISTOLOCHIA CHILENSIS ALEJANDRO URZUA and LUIS PRESLE Laboratorio de Quimica Ecol6gica, Departamento

de Quimica, Universidad de Santiago de Chile, Casilla 307, Santiago-2 Chile

(Received in revised form 23 March 1993) Key Word Index-Aristolochia

Abstract-Aristolochia austrobailignan-7.

chilensis has

chilensis; Aristolochiaceae;

yielded

the

new

INTRODUCTION

Aristolochia chilensis Miers is a summer-deciduous low creeping perennial herb ranging southwards from Caldera in Northern Chile (27”s latitude) to beyond the latitude of Santiago (34”s). It is known by the vernacular names ‘Oreja de Zorro’ (fox ear) and ‘hierba de la Virgen Maria’ (Virgin Mary’s herb) and a decoction of its roots is used to reduce excessive lochia (puerperal secretions) [ 11. Sesquiterpene hydrocarbons, 2,5-diaryl-3,4dimethyltetrahydrofuranoid lignans and 4-aryltetralones have been isolated from the roots [2-41. We have now studied some of the minor components of this plant, from which we have obtained the new 2,5-diaryl-3,4dimethyltetrahydrofuranoid lignan, 3-epi-austrobailignan-7 (1). RESULTS AND DISCUSSION

3-epi-Austrobailignan-7 (1) was obtained as an optically inactive, amorphous solid, affording the same UV and mass spectra as those of austrobailignan-7 (2) [S]. The 200 MHz (CDCl,) NMR spectrum showed significant differences in the signals for Me-3, H-3 and H-2 in comparison with that of austrobailignan-7 (2) [S]. The notable feature of the spectrum of 1 is the doublet at S 1.02

Me

roots; 3-epi-austrobailignan-7.

2,5-diaryl-3,4-dimethyltetrahydrofuranoid

lignan

3-epi-

(6H) indicating a cis-relationship between Me-3, Me-4 on one hand and H-2, H-5 on the other, characteristic of mesoand quasi-meso-2,5-diaryl-3,4_dimethyltetrahydrofuranoid lignans [3]. Acetylation of 1 with acetic anhydride-pyridine afforded the acetyl derivative with a [M] + at m/z 384.1574 confirming the molecular formula Cz2Hz406. Finally, the relative position of the aromatic hydroxyl and methoxyl substituents was settled through a partial NMR NOE study that showed reciprocal NOES between the C-3’ methoxyl (63.91) and H-2’ (67.04).

EXPERIMENTAL

Extraction and isolation. Aristolochia chilensis Miers (0.5 kg, dry roots) was collected in Lo Prado Pass, 10 km from Santiago, in June 1991. A voucher specimen is deposited in the herbarium of the Natural History Museum in Santiago (voucher SGO 077867). The plant material was dried, powdered and extracted successively with petrol and EtOH at room temp. The EtOH extracts were coned, leaving a residue (20 g). This extract was fractionated by CC over silica gel, using hexane gradually enriched with EtOAc. The frs were monitored by TLC on silica gel, using hexane-EtOAc (4: 1) and CHCl,, and spraying with 33% H,SOI. Final purification was

Me

Me

OMe

H

OMe

874

875

Short Reports achieved by silica gel TLC using CHCI, containing 1% MeOH. 3-epi-Austrobailignan-7 (I). Amorphous solid, 8 mg. UV AL:” nm: 234, 282 (log c 4.02, 3.85). ‘HNMR (200 MHz CDCl,): S7.04 (d, J=1.4 Hz, lH, H-2’), 6.98-6.77 (m, 5 Ar-H), 5.96 (s, 2H, 0-CH,-O), 5.60 (s, lH, exchangeabie with D,O, OH), 4.46 (d, d = 6.5 Hz, 2H, H-2 and H-5), 2.27 (m, 2H, H-3 and H-4), 1.02 (d, J=6.7 Hz, 6H, Me-3 and Me-4). MS m/z (rel. int.): 342 (40), 257 (2), 192 (70), 190 (lOO), 177 (S), 175 (21), 145 (31). ‘HNMR NOE: H-2’ to MeO-3, 21.3%; MeO-3’ to H-2’, 17.2%. &etyl-3-epi-AustrobazQnun-7. Compound 1 (6 mg) was acetylated with Aq,O-pyridine yielding an amorphous solid, 7 mg. ‘H NMR (200 MHz, CDCI,): 67.07 (d, .I =1.4Hz, lH, H-2’) 7.04-6.77 (m, 5 Ar-H), 5.95 (s, 2H, 0-CH,-0), 4.53 (d, J = 6.1 Hz, lH, H-2 or H-5), 4.47 (d, J =7.1 Hz, lH, H-5 or H-2), 2.31 (s, 3H, Me-GO), 2,31 (m, 2H, H-3 and H-4), 1.06 (d, J =6.7 Hz, 3H, Me-3 or Me-4),

1.00 (d, J = 6.7 Hz, 3H, Me-4 or Me-3). MS m/z (rel. int.): 384.1574 ([Ml+, 20), 342 (7), 192 (lot)), 190 (74). Acknowledgements-This

DICYT, Universidad

research was supported de Santiago de Chile.

by

REFERENCES

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117. 5. Murphy, S. T., Ritchie, E. and Taylor, W. C. (1975) Aust. J. Chem. 28, 8 I.