Flavonoids, flavonolignans and a phenylpropanoid from Onopordon corymbosum

Phytochemistry,Vol. 29, No. 2, pp. 629631, 1990. Printed in Great Britain.

FLAVONOIDS,

0031-9422/X1 %3.00+0.00 0 1990Pergamon Press plc

FLAVONOLIGNANS ONOPORDON

AND A PHENYLPROPANOID CORYMBOSUM

FROM

M. Luz CARDONA, BEGORA GARCIA, Jo& R. PEDRO* and JORGE F. SINISTERRA Department of Organic Chemistry, Faculty of Chemistry, University of Valencia, Burjassot, Valencia, Spain (Received in revised form

Key Word Index-Onopordon

30

June 1989)

corymbosum;Compositae; aerial parts; flavonoids; flavonolignans; phenylpropanoid.

Abstract-The aerial parts of Onopordon corymbosum afforded seven flavonoids, and two flavonolignans, hydnocarpin and the new 5”-methoxy-hydnocarpin.

INTRODUCTION Onopordon corymbosum Willk. is a member of a small genus in the tribe Cynareae (Compositae) [l], from which flavonoids [2, 31 and sesquiterpenes [4-S] have been isolated. From 0. corymbosum we have already reported several sesquiterpenes [9] and in this paper we report the

isolation of several flavonoids, a new natural phenylpropanoid and two flavonolignans, one being new. RESULTS AND DISCUSSION

Chromatographic separation of the material from the ether extract of a concentrated methanolic extract of 0. corymbosum yielded compounds l-10. The structures of the known flavones pectolinarigenin 1 [6], acacetin 2 [ 101, hispidulin 3 [ 111,chrysoeriol4 [12], apigenin 5 [ 133 and luteolin 6 [14] were determined by spectroscopic methods [15, 163. The compound 7, was an acacetin glycoside, identified as its 7-0-/?-D-methylglucuronide by spectroscopic methods [17] and acid hydrolysis. This compound has been isolated only twice in nature, from Clerodendron infortunatum (Verbenaceae) [ 181 and Onopordon macracanthum (Compositae) [ 173. The compound 8 was a phenylpropanoid, identified as 3-(3,4-dihydroxyphenyl)- 1-propanol by spectroscopic methods. This is the first report of this phenylpropanoid as natural product. Nevertheless synthetic 8 has been described and has biological activity as cotyledon factor in Lactuca satiua (Compositae), i.e. it acts as a synergist

3-(3,4-dihydroxyphenyl)-I-propanol

doublet (6 5.00) typical for a benzylic methyne substituted by oxygen and its typical trans-coupling (J=7.7 Hz) indicates the presence of a trans-substituted 1,4-dioxane ring between the flavonoid skeleton and the phenyl ring. In support of this, the peak at m/z 180 in the mass spectrum can be rationalized in terms of a retroDiels-Alder reaction in the dioxane ring. Consequently 9 is identified as hydnocarpin. This flavonolignan was first isolated from Hydnocarpus wightiana [21, 221 (Flacourtiaceae) and then from Cassia absus (Leguminosae) [23]. The ‘HNMR of 10 showed the presence (ca 50%) of two very similar products (two doublets at 65.00 and 64.99 for benzylic methynes substituted by oxygen and two doublets at 67.07 and 67.08 for H-5’ in a luteolin framework). One is hydnocarpin (m/z 464) and the other methoxyhydnocarpin (m/z 494). The ions at 210,192,182, 181, 180, 167 and 154, which appeared at m/z 180, 162, 152, 151, 150, 137 and 124 respectively in hydnocarpin indicated that the additional methoxyl group is present on the phenyl ring. From a comparison with alternative substitution patterns, the multiplicity (a singlet) and the chemical shifts (66.74) of the two remaining aromatic protons indicated a 4-hydroxy-3,5-dimethoxy-substituted phenyl ring. Consequently 10 is, in fact, a mixture of hydnocarpin and 5”-methoxyhydnocarpin. This is the first report on the latter flavonolignan. Biogenetically hydnocarpin and 5”-methoxyhydnocarpin may be derived from luteolin through a radical coupling process with coniferyl alcohol and syringenin [24].

on gibberellin-induced lettuce hypocotyl elongation [ 191. Besides, the lettuce natural cotyledon factor is the closely related 3-(4-hydroxy-3-methoxyphenyl)-1-propanol (di-

EXPERIMENTAL

was collected, classified and extracted as described previously [9]. The Et,0 re-extract was subjected to chromatography on silica gel column using mixtures of hexane-CH,CI,-EtOAc as eluent. Six main fractions groups A-F were obtained, with the following proportion of CH,CI,-EtOAc:A(9:1 to 17:3),B(fl:l to l:l),C(l:l to9:ll), D (9:ll to l:4), E (1:4 to 3:17) and F (3:17 to 0:lOO). Compound 7 (6 mg) crystallized directly from the group E. Repeated chromatographic process afforded: compound 1 Onopordon

hydroconiferyl alcohol) [20]. The ‘H NMR spectrum of 9 showed typical signals of a luteolin substitution pattern (H-3, 6, 8, 2’, 5’ and 6’ in Table 1). The molecular ion at m/z 464 was in agreement with a molecular formula CZ5HZ009. To complete this formula a C,-C, phenylpropane moiety with a methoxyl group was needed. The observation of a deshielded

corymbosum

(33 mg) and 2 (3 I mg) from group A; compounds 3 (70 mg), 4 (35 mg) and 5 (140 mg) from group B; compounds 3 (3 mg), 5

*Author to whom correspondence should be addressed. 629

630

M. L. CARDONA et al. 1 R’= K4=

K’

H,

K’= K’=

2 K’=KZ=KJ=H. 3

R4

K’=

K’=H.

K’=OMe.

4 K’= RZ= H. R’=OH

OH

0

OMe

K”=()Me

5

R’ = K2= RJ= t,.

fj

~~ = K* = ,,

K3=Oti K’=OMe

KJ, OH

K’= K4= OH

7 K’ = Methyl Glur H2,

KJ= H,

K”=OMe

OH

8 HO OH

OH

0

Table

I. ‘H NMR chemical

H 2’ i1 5’I, ,/ II

K

shifts of compounds

9

9 and lO* IO

7.65, d, J = 1.7 Hz 6.87 6.80 7.07, 7.59, 7.02, dd, d, s J J==8.0 7.4Hz and 1.7 Hz

1.65, d, J = 1.7 Hz 6.74, 6.14, dd, 7.08, 7.59, s J J==8.0 d, 7.4Hz and 1.7 Hz

AB system, J = 8.2 Hz 3 8 6 ArCH ArCH-CH MeO-3” MeO-5”

11 6.86, 6.50, 6.18, 5.00, 4.25, 3.17.

s d, J = 1.6 Hz d, J=1.6Hz d, J = 1.7 Hz m s

6.86, 6.50. 6.18, 4.99. 4.25. 3.71. 3.77,

*The spectra have been measured in DMSO-d, values are given in 6 (ppm) relative to TMS.

(8 mg) and 6 (12 mg) from group C; compounds 5 (34 mg), 6 (10 mg) and 9 (10 mg) and a mixture of 9 and 10 (5 mg) from group D; and several sesquiterpenes [9] and compound 8 (20 mg) from group F. 3-(3,4-dihydrox~phen~l)-1-Propanol 8. Ms m/z (rel. int.) 168 ([Ml’, 39.50/o), 123 (53.6%), 97 (loO%), 69 (56.7%) 45 (77.8%) and 41 (78.7%) ‘HNMR (200 MHz, CDCI,-Me,CO-d, 1:1) 67.05 (s, phenolic HO-), 6.98 (s, phenolic HO-). 6.55 (d. J = 7.9 Hz, H-5’). 6.52 (d, J = 1.1 Hi, H-2’) 6.34 (dd, J =7.9 and 1.1 Hz, H-6’), 3.44 (t, J=6.5 Hz, H-l), 3.05 (s, alcoholic HO-), 2.36 (I, J=7.4 Hz, H-3) and 1.62 (4. J=6.9 Hz, H-2); “CNMR

s d, J = 1.6 Hz d, J= 1.6 Hz d, J = 7.8 Hz nr s s

at 200 MHz. All chemical

shift

(50 MHz, CDCI,-Me,CO-d, 1: 1) 6142.7 (C-3’, or C-4’). 140.8 (C-4’ or C-3’), 132.2 (C-l’), 117.9(C-6’), 113.5 (C-2’ or C-Y), 113.2 (C-5’ or C-2’). 59.6 (C-l), 32.7 (C-3) and 29.5 (C-2). Hydnocarpin 9. Mp 278-280’, UV kz:p” 271, 285 (sh), 340; NaOMe 278, 295, 315 (sh), 370; NaOAc 277, 292 (sh), 312, 372; NaOAc/H,BO,, 267, 345; AlCI, 275, 297. 358, 387; AICI,/HCl 262, 280, 295, 358, 375. 5”-Methoxyh~dnocarpin 10. UV Az:p 271, 340, NaOMe 278, 292(sh), 312(sh), 375; NaOAc278,318,374; NaOAc/H,BO, 271, 342; AICI, 262, 278. 298, 357. 382; AICI,/HCI 262, 280,295, 352, 380.

Phenylpropanoid Table

2. Mass spectral

from Onopordon corymbosum

fragmentation

patterns

of compounds

631 9 and 10

Ion

9 m/z (%)

10 m/z (%)

WI’

464 (36.5) 446 (20.4)

494 (17.4) 476 ( 4.8)

[M-H20]+ [M-ArCH,]+ [M -ArC=CCH,OH]+=[A]’ [A-HCO]+ [ArCH=CHCH,OH]=[B]+ [B-H,O]+ [B-CO]+ [B - HCO] + [B-H,CO]+ [ArCH,] + [ArH] + [ArCH,-H,O]+ [ArCH,-H+CG]+

180 162 152 151 150 137 124 119 91

Acknowledgements-Financial support by the Comision Asesora de Investigation Cientifica y Ticnica (CAICYT, Grant No. 559/84) is gratefully acknowledged. We thank Prof. J. Alcover (Department of Botany, Faculty of Biological Sciences, University of Valencia, Spain) for identification of plant material.

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