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Boletín de la Sociedad Chilena de Química

versión impresa ISSN 0366-1644

Bol. Soc. Chil. Quím. v.45 n.1 Concepción mar. 2000

http://dx.doi.org/10.4067/S0366-16442000000100007 

CONSTITUENTS OF CHUQUIRAGA ATACAMENSIS AND
C. ULICINA

M. HOENEISEN1*, ALEJANDRA ROJAS1, M. BITTNER1, J. BECERRA1,
M. SILVA1, J. JAKUPOVIC2

1Universidad de Concepción, Laboratorio de Química de Productos Naturales,
Departamento de Botánica, Casilla 2407, Apartado 10, Concepción, Chile.
2Institute for Organic Chemistry, Technical University of Berlin, D-10623 Berlin 12, Germany (Received: August 23, 1999 - Accepted: October 14, 1999)

ABSTRACT

Two Chilean Chuquiraga species afforded mainly known compounds. Chuquiraga atacamensis gave in addition a new triterpene. The structures were elucidated by means of spectroscopic methods.

KEY WORDS: Chuquiraga atacamensis, C. ulicina, Asteraceae, taraxas-20(21)-en-3b, 6-diol

RESUMEN

De dos especies de Chuquiraga se aislaron varios compuestos conocidos. De Chuquiraga atacamensis se aisló además un triterpeno nuevo. Las estructuras se determinaron basadas en sus datos espectroscópicos.

PALABRAS CLAVES: Chuquiraga atacamensis, C. ulicina, Asteraceae, taraxas-20(21)-en-3b, 6-diol

INTRODUCTION

The genus Chuquiraga comprises 19 species of xerophyllous bushes of South America1). Some of them are used for ornamental purposes, as fuel and/or for their medicinal properties. They are also of indirect economic interest because they are dominant species in regions with lack of water in which there are only few plant species and therefore they are important for the fauna of that ecosystem.

We are only aware of one chemical study on the genus, C. spinosa2). In Chile this genus is represented by six speccies3).

In a continuation of our investigation of Chilean Asteraceae4-11) we have now studied Chuquiraga atacamensis O.K. and C. ulcina (H. et A.) H. et A. ssp. acicularis (D. Don) Ezc. and the results are discussed in this paper. Chuquiraga atacamensis is a bush 30-60 cm tall which grows at 3000-4500 m above sea level, and is used as fuel and in folk medicine. Chuquiraga ulcina is a bush that grows in sandy soils from sea level to 1000 m in the Coquimbo Province and also in Aconcagua (Chile).

EXPERIMENTAL

Chuquiraga atacamensis was collected in September 1986, 38 Km before San Pedro de Atacama on the Calama-San Pedro de Atacama road, Chile, 3500 m above sea level, voucher R. Rodríguez, N 333 and deposited in the Herbarium of the University of Concepción, Chile. The air dried aerial parts (leaves, stems and flowers, 1862 g) were extracted and worked up as reported previously11). The extract was separated by column chromatography (silica gel) to give 10 fractions: 1 (hexane), 2 (hexane/EtOAc, 11:1), 3 (hexane/EtOAc, 9:1), 4 (hexane/EtOAc, 3:1), 5 (hexane/EtOAc, 1:1) 6 (hexane/EtOAc, 1:3), 7 (EtOAc), 8 (EtOAc/MeOH, 11:1), 9 (EtOAc/MeOH, 9:1), 10 (MeOH). The interesting fractions were further purified by preparative TLC on silica gel plates (silica gel 60 F 254) and gave 40 mg lupeol, 5 mg vanillin, 8 mg betulin 1,10 mg erythrodiol 2 and 8 mg of compound 3.

Compound 3: HRMS: m/z (%) 442.381 (M) (95) (calc. for C30H50O2 442.381); 424 (M-H2O)(26); 409(424-Me)(13); 391 (409-H2O)(8); 218(45); 207(46); 205(75); 189(56); 187(85); 57(100).

A similarly prepared extract of Chuquiraga ulicina var. acicularis (1800 g) collected in March 1987 in the Elqui valley on a hillside facing Rivadavia, Chile, voucher R. Rodríguez, N 67, was separated by column chromatography (silica gel) to give 10 fractions: 1 (hexane), 2 (hexane/EtOAc, 11:1), 3 (hexane/EtOAc, 9:1), 4 (hexane/EtOAc, 3:1), 5 (hexane/EtOAc, 1:1), 6 (hexane/EtOAc, 1:3), 7 (EtOAc), 8 (EtOAc/MeOH, 11:1), 9 (EtOAc/MeOH, 9:1), 10 (MeOH). The more interesting fractions were further purified by preparative TLC on silica gel plates (silica gel 60 F 254) and gave 11 mg umbelliferone, 30 mg lupeol, 7 mg taraxasterol, 5 mg lupeyl acetate, 4 mg b-amyrin, 3 mg a-amiryn acetate 8 mg b-amyrin acetate. The known compounds were identified by comparison of their spectral data with authentic spectra or literaure data.

TABLE I. 1H and 13C-NMR data of compound 3 (400 MHz and 100 MHz, CHCl3).


1H
13C

1 1.70 m 0.94 m 1 40.74t
2 1.65 (2H) 2 27.55 t
3 3.15 dd (8.8) 3 79.12 d
4 39.59 s
5 0.70 d 5 55.56 d
6 4.53 br ddd (2,3,3) 6 69.04 d
7 1.63 (2H) m 7 42.05 t
8 42.56 s
9 1.34 m 9 51.08 d
10 36.69 s
11 1.62 m 1.34 m 11 21.75 t
12 1.65 (2H) m   12 27.75 t
13 1.71 m   13 38.38 d
      14 40.11 s
15 1.82 br ddd 1.00 m 15 27.12 t
16 1.29 m 1.21 m 16 36.64 t
      17 34.37 s
18 1.08 m   18 48.83 d
19 1.58 m   19 36.28 d
      20 139.82 s
21 5.26 br d (7) 21 118.88 d
22 1.74 m 1.56 m 22 42.18 t
23 1.06 s   23 27.59 q
24 1.15 s   24 16.86 q
25 1.23 s   25 17.83 q
26 1.36 s   26 17.19 q
27 0.93 s   27 15.04 q
28 0.75 s   28 17.66 q
29 0.99 d (7) 29 22.50 q
30 1.64 br s   30 21.60 q

TABLE II. COLOC results for compound 3.


dH
dC

0.70 (H-5) 16.86 (C-24); 17.83 (C-25); 36.69 (C-10); 39.59 (C-4); 79.12 (C-3)
0.75 (H-28) 34.37 (C-17); 36.64 (C-16); 42.18 (C-22); 48.83 (C-18)
0.93 (H-27) 27.12 (C-15); 38.38 (C-13); 40.11 (C-14); 42.56 (C-8)
0.99 (H-29) 36.28 (C-19); 48.83 (C-18); 139.82 (C-20)
1.06 (H-23) 16.86 (C-24); 39.59 (C-4); 55.56 (C-5); 79.12 (C-3)
1.15 (H-24) 27.59 (C-23); 39.59 (C-4); 79.12 (C-3)
1.23 (H-25) 36.69 (C-10); 40.74 (C-1); 51.08 (C-9)
1.36 (H-26) 40.11 (C-14); 42.05 (C-7); 42.56 (C-8)
1.64 (H-30) 118.88 (C-24); 139.82 (C-20)
3.15 (H-3) 16.86 (C-24); 27.55 (C-2)
4.53 (H-6) 36.69 (C-10); 39.59 (C-4)
5.26 (H-21) 21.60 (C-30); 34.37 (C-17); 36.28 (C-19); 42.18 (C-22)

TABLE III. NOE/DIFF results for compound 3.


H    

3   H-5 (5%); H-23 (2%)
5   H-3 (5%); H-6 (4%)
6   H-5 (3%); H-23 (5%); H-24 (1%)
23   H-3 (6%); H-5(5%); H-6 (10%); H-24 (3%)
24   H-23 (3%); H-25 (6%)
25   H-24 (6%); H-26 (6%)
26   H-13 (8%); H-15 (5%): H-25 (7%)
27   H-9 (5%); H-18 (8%)
28   H-13 (5%); H-15 (4%); H-19 (4%); H-22 (4%)
29   H-30 (6%)

RESULTS AND DISCUSSION

The aerial parts of Chuquiraga atacamensis gave, in addition to vanillin, lupeol, betulin 1 12), erythrodiol 213), and the new triterpene 3 (taraxas-20(21)-en-3b,6-diol).

The 1H-NMR spectrum of 3 (Table I) showed eight methyl signals - seven tertiary singlets (including an olefinic one) and one secondary doublet. Only three further signals appeared well resolved corresponding to an olefinic and two methinic protons on oxygen bearing carbons. All other signals were overlapping in the high field region. The 13C-NMR spectrum (Table I) confirmed the presence of a double bond and two secondary alcohols. Taking into account the multiplicities of signals in the 13C-NMR spectrum the molecular formula was C30H50O2. Thus, a pentacyclic compound was present. The position of the signals in the 1H-NMR spectrum were deduced from the correlation peaks in the 1H/13C hetero correlated spectrum. From the homo COSY experiment several sequences were established. However, the most informative were the results of the hetero long range correlation (COLOC) through two or three bonds (Table II). The logical connection of all spectroscopic data led to the structure of a taraxane derivative 3. The positions of the hydroxy groups were deduced from the COLOC results, particularly from the correlation between H-3 and C-24 and between H-5, H-6, H-23 and H-24 each one with C-4. The results of the NOE difference spectra made the assignment of the configuration possible (Table III).

The aerial parts of Chuquiraga ulicina ssp. acicularis gave umbelliferone14), lupeol, taraxasterol, lupeyl acetate, b-amyrin, a-amyrin acetate and b-amyrin acetate.

Lupeol, taraxasterol and b-amyrin are present in the flowers of several Asteraceae and have anti-inflammatory effects15). Because the inhibitory effects against TPA-induced inflammation have been demonstrated to closely parallel those against tumor-promotion by the same compound, and because the Asteraceae studied by us contain these triterpenoids possessing strong anti-inflammatory activity, the extracts of Asteraceae flowers and the triterpenoids from the flowers may be of importance from the viewpoint of the chemoprevention of cancer16).

ACKNOWLEDGEMENTS

The authors thank Fondecyt Chile, project N 1941106 and Dirección de Investigación project N 97.111.014-1.3, Universidad de Concepción, Chile. They are also grateful to Nancy Paredes and Fabiola Ríos for technical assistance. M.H. thanks the Universidad de Concepción for a scholarship.
___________________________________
*To whom correspondence should be addressed.

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