Quinovic acid glycosides from Uncaria guianensis

Phytmkmisfry. Vol. 30. No. 5, pp. 1635 1637. 1991 Printed in Gmat Britain.

QUINOVIC

0031.9422/91 53.00+0.00 Pcrgamon Press plc

ACID GLYCOSIDES

FROM

UNCARIA

GUIANENSIS

ANA M. Y~PEZ P., OLGA LOCK DE UGAZ, CARMEN M. ALVAREZ A., VINCENZO DE FEO,* RITA AQUINO,* FRANCESCO DE SIMONE* and COSIMO PIZZA* Departamento de Quimica, Pontificia Universitad Catolica del Peru, Apartado 1761, Lima, Perk lDipartimento di Chimica delle Sostanze Naturali, Universitl di Napoli “Federico II”, Via D. Montesano, 49-80131 Napoli, Italy (Received in revised form 2 October 1990) Key Word Index- Uncoria

guianensis;

Rubiaeeae; bark; quinovic acid glycosides; structural determination.

Abstract-From the bark of Uncaria guianensis, two new quinovic acid glycosides, quinovic acid 3/?-0-b-Dquinovopyranoside and quinovic acid 38-O-/?-D-fucopyranosyl-(27+ It/?-D-ghtcopyranosylester, have been isolated, in additton to known quinovic acid 3~-O-[/%D-glucopyranosyl-(l+3)-/?-D-fucopyranosy~]-(27-r I)-b-D-ghCOppnOSy1 ester and quinovic acid 3/j’-0-B-D-fucopyranoside. Their structures were elucidated by spectral and chemical studies.

INTRODUCTION

guianensis (Aubl.) Gmel. is a plant of the Amazon area, commonly known as ‘garabato’ and ‘unganangi [I]. The aqueous extract of the bark of this plant is widely used in traditional Peruvian medicine for the treatment of cancer, arthritis, diabetes and as a potent anti-inflammatory agent. A number of alkaloids were previously reported in genus Uncaria [2-51 and particularly in U. guianensis [2, 33, while no phytochemical or pharmacological work has been done on the non-alkaloidal constituents of this species. This work is part of a series of studies on glycosidic metabolites from Rubiaceae of the South American flora used in folk medicine [69]. This family contains, in addition to other metabolites, quinovic acid glycosides showing varied structures, among which four groups can be discerned, including glycosides having a C-3, a C-28, a C-3,28 or a C-3,27 glycosylation pattern [6-93. The last group of compounds is rare in nature and has been found only in Uncaria tomentosa and in Guettarda platypoda [6, 73. We report the isolation of quinovic acid glycosides with a C-3.27 (1 and 4) or a C-3 (2 and 3) substitution pattern from U. guianensis. Uncaria

R’O R’

1

GIG

2

H

RESULTS AND DlXUS!3lON

The bark of U. guianensis was extracted with ethyl acetate. The residue, after chromatography on a silica gel column and HPLC, yielded compounds 1-4. Their structures were determined by FABMS, ‘H and “CNMR measurements and sugar analysis. Glycoside 1 has previously been described in U. fomentosa [7], glycoside 2 in Guettarda platypoda [IO], whereas 3 and 4 are new natural products. On acid methanolysis, followed by GLC, methylglycoside and methylfucoside were obtained in the ratio 1: I for 4, and 2: 1 from I, whereas compound 3 gave a CC pattern characteristic of quinovose and compound 2 of fucose. The FABMS, in negative ion mode, of 2 and 3 showed the same fragmentation patterns. Both compounds gave a quasi-molecular anion at m/z 631 [M-H]-, and a fragment at m/z 485 [(M - H) - 146]- showing the loss of 1635

‘OH

H

PH 4

GlC

0 HO

%

1’ OH

1636

A. M. YErrz P. er ol

Table I. “C NMK data of compounds 3 and 4 (CD,OD) Aglyconc carbons -~. 1 2 3

4

5 h

7 Y

0

IO II 12 13 14 IS 16 17 IX 19 ‘0 21 22 23 ‘4 25 26 27 28 20 30 Sugar carbons I’ 3’ 3’ 4, 5’ 6’

3

4

3Y Y 27.0 YO5 40.3 56.9 lY.3 37 0 40 8 4x.0* 3x.3 23.9 129.2 135.4 59.2 26.5 25.7 3X.8* 55,s 40 I 31.9 31.2 37.6 19.3 2X.6 16.X IX.1 179.5 I x2.0 17.6 21.4

40.0 27. I 90.7 40.3 57.0 lY.3 3x.0 41.0 4X. I * 3X.3 23.9 130.9 133.4 57.5 26.6 25.H 49.7; 55.4 40.1 38.1 3_l.2 37.1 19.2 28.6 16.9 IX.1 17x.0

Quinovose

182.0 17.0 21.4

at C-3

106.4 76.0 7X.I 71.4 71. I

IX.1

1” 2” 3” 4” 5” 6”

DEPT

CH, CH, CH C

CH CH, CH2 C CH C CH, CH C C CH, CH, C CH CH CH CH, CH, Me Me MC Me C C MC Me

Fucose at C-3 107.0 73.1 75.4 73.0 71.5 17.1

CH CH CH CH CH CH,

Glucose at C-27 95.7 74 1 78.6 71.6 78.4

CH CH CH CH CH

62.9

CH,

*L’nder methanol signal

a deoxyhexose unit. We also observed peaks at m/z 587 and 441, corresponding to the facile loss of a carboxyl group starting from the tnji 631 and 485 peaks, respectively. The molecular formula C,,H,,O, for 2 and 3 and C,,H,,O, for the aglycone were deduced by FABMS and 13C and DEPT “CNMR data. The FAB mass spectrum of 4 showed a quasimolecular anion at m/z 793 [M-H]indicating the presence of an extra glucose unit with respect to 2 and 3; a fragment at m;z 647 [(M -- H) - 146]-, suggesting the loss of a deoxyhesosc

unit without

the glycosidic oxygen; a

Me-23 (3H. .\) Mc-76 (3H. 5) Me-2Y and 30 (6H. d. sharp) Me-25 (3H. s) Me-24 (31-L s) H-12 (IH. ~1) Sug:ir proIon QUI-Me’ (3H. .\) Fuc-Me* (3H. \I QUI-H- I ‘+ ( I Cl.