Divergioic Acid, a Triterpene from Vochysia divergens

Abstracts

A new lupane triterpene, divergioic acid, has been isolated from the stem bark of Vochysia divergens together with beta-sitosterol, betulinic, sericic and 24-hydroxytormentic acids and the (28 -> 1) beta-D-glucopyranosyl ester of the latter. The structure of divergioic acid was elucidated by spectroscopic techniques and characterized as 2alpha,3beta,6beta-trihydroxy-lup-20(29)-en-28-oic acid.

Vochysia divergens; Vochysiaceae; lupene; divergioic acid

Um novo triterpeno lupânico, ácido divergióico, além de beta-sitosterol, ácidos betulínico, serícico e 24-hidroxitormêntico, e o éster (28 -> 1) beta-D-glucopiranosílico do último, foram obtidos a partir da casca do caule de Vochysia divergens. A estrutura do ácido divergióico foi elucidada por meio de técnicas espectroscópicas, e caracterizada como sendo o ácido 2alfa,3beta,6beta-trihidroxi-lup-20(29)-en-28-óico.

Article

Divergioic Acid, a Triterpene from Vochysia divergens

Sonia C. Hess^a, and Franco Delle Monache^b*

^a

Departamento de Morfofisiologia/CCBS, Universidade Federal de Mato Grosso do Sul, C.P. 549, 79070-900 Campo Grande - MS, Brazil;

^b Centro Chimica dei Recettori del C.N.R., Istituto di Chimica, U.C.S.C., Largo Francesco Vito 1, 00168 , Roma, Italia

Um novo triterpeno lupânico, ácido divergióico, além de b-sitosterol, ácidos betulínico, serícico e 24-hidroxitormêntico, e o éster (28 ® 1) b-D-glucopiranosílico do último, foram obtidos a partir da casca do caule de Vochysia divergens. A estrutura do ácido divergióico foi elucidada por meio de técnicas espectroscópicas, e caracterizada como sendo o ácido 2a,3b,6b-trihidroxi-lup-20(29)-en-28-óico.

A new lupane triterpene, divergioic acid, has been isolated from the stem bark of Vochysia divergens together with b-sitosterol, betulinic, sericic and 24-hydroxytormentic acids and the (28 ® 1) b-D-glucopyranosyl ester of the latter. The structure of divergioic acid was elucidated by spectroscopic techniques and characterized as 2a,3b,6b-trihydroxy-lup-20(29)-en-28-oic acid.

Keywords: Vochysia divergens, Vochysiaceae, lupene, divergioic acid

Introduction

Vochysia divergens Pohl (Vochysiaceae) is a tree commonly found in wet soils of the "pantanal" of Mato Grosso do Sul, Brazil, and used in folk medicine against infections and asthma¹. In previous reports we described the isolation of

b-sitosterol, betulinic and sericic acids from the stem bark, as well as the antifungal

² and antibacterial

³ activities of sericic acid. In this communication we report the structure elucidation of divergioic acid, a novel lupene. 24-Hydroxytormentic acid and its glucopyranosyl ester were also isolated.

Results and Discussion

In addition to

b-sitosterol, betulinic and sericic acids, the reinvestigation of the EtOH extract from the stem bark afforded 24-hydroxytormentic acid and its glucopyranosyl ester in high yield (see Experimental), and a new triterpene, which was named divergioic acid (

1). The molecular formula C

₃₀H

₄₈O

₅ was deduced from the NMR data and the molecular ion (M

⁺ at

m/z 488) in the mass spectrum. The

¹H-NMR spectrum exhibited signals at d 4.97 (1 H), d 4.80 (1H) and d 1.81 (3 H), characteristic of triterpenes with a lupene skeleton. In addition, five methyl singlets and signals for three methines on hydroxyl bearing carbons (d 4.86, br s; d 4.30, dt and d 3.44, d) were present. By irradiation at d 4.30, the signal at d 3.44 became a singlet. These findings suggested a lup-20(29)-ene gross structure with two OH in position 2 and 3, and an additional hydroxyl. In accordance, the

¹³C-NMR spectra (

Table 1) showed the appropriate signals for the isopropylene moiety and for three hydroxylated carbons. Comparison of

¹³C-NMR data of

1 with those of betulinic acid,

2

⁴ (

Table 1) revealed a good agreement of the values for the carbons of rings C/D/E. Furthermore, the signals due to A/B ring carbons were found to be very similar to those of 2a,3b,6b,19-tetrahydroxy-urs-12-en-28 oic acid,

6

⁵.

Table 2 reportes the main long-range C-H and H-C connectivities found in the long-range HETCOR spectrum and by selective INEPT experiments, respectively, which are in agreemen with the structure proposed for

1. Therefore, divergioic acid (

1) was assigned the structure 2a,3b,6b-trihydroxy-lup-20(29)-en-28-oic acid and is the first example of a lupane possessing the rare 6-OH group.

Experimental

Plant material

Vochysia divergens Pohl (Vochysiaceae) was collected in Corumba (Mato Grosso do Sul, Brazil) and identified by G. A. Damasceno Jr. (DAM/CEUC/UFMS) and Arnildo Pott (CPAP/EMBRAPA). A voucher specimen is deposited in the herbarium of the Centro Universitario de Corumba/UFMS (Corumba, MS, Brazil) under number 0500.

Extraction and isolation

The powdered stem bark (4.0 kg) was exhaustively extracted with cold EtOH. After evaporation, a mixture of MeOH/H₂O, 95:5 (250 mL) was added to a part (20 g) of the EtOH extract, and filtered. Evaporation of the soluble portion (14 g) and washing with cold CHCl₃ yielded two fractions, B (soluble, 8 g) and C (insoluble, 6 g). CC of fraction B on SiO₂ yielded

b-sitosterol (30 mg), betulinic acid,

2 (300 mg), by elution with a gradient of EtOAc in hexane; impure

1, a mixture of sericic (

3) and 24-hydroxytormentic (

4) acids and the impure glucoside of

4,

5 (4.2 g) were obtained by elution with a gradient of MeOH in EtOAc. CC of fraction C (SiO

₂; gradient of MeOH in EtOAc) gave

2 (20 mg), impure

1 (80 mg) and a mixture (2 g) of

3,

4 and

5. Extended chromatography (SiO

₂, hexane/EtOAc, 7:3) of the pooled impure

1 afforded divergioic acid (42 mg). Repeated CC (SiO

₂; CHCl

₃/MeOH/H

₂O 19.5:8.5:2.3, and EtOAc/MeOH, 9:1) of the fractions containing impure

3,

4 and

5 gave pure

3 (500 mg), pure

4 (700 mg), a mixture of

3 and

4 (3.2 g) and the (28 ® 1) b-D-glucopyranosyl ester

5 (300 mg).

¹³C-NMR data for

3 (2a,3b,19a,24-tetrahydroxyolean-12-en-28 oic acid) were not available in the literature, and the signals were attributed by comparison with the respective data for rings A/B of

4 (2a,3b,19,24-tetrahydroxyurs-12-en-28 oic acid)

⁶ and for rings C/D/E of arjungenin (2a,3b,19a,23-tetrahydroxyolean-12-en-28 oic acid)

⁷. Reaction of

3 with diazomethane afforded the respective methyl ester,

¹H-NMR data were in agreement with data previously published

⁸.

Divergioic acid. 1 Mp 155-6 °C; [

a]

_D

²⁰ -7° (

c 3.0, MeOH);

¹H-NMR (300 MHz, Pyridine-

d

₅), d: 4.97 and 4.80 (br s, H

₂-29), 4.86 (brs, H-6), 4.30 (dt, H-2), 3.57 (m, H-19), 3.44 (d, J = 9.3 Hz; H-3), 2.90 (m, H-13), 2.63 (m, H-16a), 2.27 and 2.25 (m, H-22a and H-21a), 1.81 (s, Me-30), 1.77 (s, Me-25), 1.69 (s, Me-26), 1.60 (s, Me-24), 1.46 (s, Me-23), 1.08 (s, Me-27);

¹³C-NMR (75 MHz, Pyridine-

d

₅) see

Table 1.

Known triterpenes

Sericic acid, 3: [

a]

_D

²⁰ +33° (

c 0.3, MeOH), Mp 280 °C (dec.), IV and MS data were comprable to those in Ref. 8.

¹³C-NMR (75 MHz, Pyridine-

d

₅), d:

C-1 47.2;

C-2 68.4;

C-3 85.6;

C-4 43.7;

C-5 56.5;

C-6 19.2;

C-7 33.5;

C-8 39.9;

C-9 48.3;

C-10 38.3;

C-11 28.9;

C-12 123.5;

C-13 144.6;

C-14 41.9;

C-15 29.1;

C-16 28.2;

C-17 45.9;

C-18 44.6;

C-19 81.2;

C-20 35.5;

C-21 28.2;

C-22 33.4;

C-23 23.9;

C-24 65.4;

C-25 17.2;

C-26 17.0;

C-27 24.6;

C-28 180.5;

C-29 28.5;

C-30 24.7.

24-Hydroxytormentic acid, 4: [

a]

_D

²⁰ +24° (

c 0.3, MeOH), NMR data in agreement with those previously reported were obtained

⁶;

24-Hydroxytormentic acid (281)-D-glucopyranosyl ester, 5 : [

a]

_D

²⁰ -9° (

c 0.7, MeOH), NMR data in agreement with those previously reported were obtained

⁶.

Acknowledgements

The authors are grateful to G.A. Damasceno Jr. and A. Pott for the botanical identification of the plant material. Thanks are due to PROPP/UFMS and CNR/Itália for finantial support.

References

Received: August 7, 1998

• 1. Pott, A.; Pott, V.J. In Plantas do Pantanal; EMBRAPA; Corumbá, Brasil, 1994.
• 2. Hess, S.C.; Brum, R.L.; Honda, N.K.; Morais, V.M.F.; Gomes, S.T.A.; Lima, E.O.; Cechinel Filho, V.; Yunes, R.A. Fitoterapia 1995, 66, 549.
• 3. Hess, S.C.; Brum, R.L.; Honda, N.K.; Cruz, A.B.; Moretto, E.; Cruz, R.B.; Messana, I.; Ferrari, F.; Cechinel Filho, V.; Yunes, R.A. J. Ethnopharm. 1997, 47, 97.
• 4. Macias, F.A.; Simonet, A.M.; Estebam, M.D. Phytochemistry 1994, 36, 1369.
• 5. Gopalsamy, N.; Vargas, D.; Gueho, J.; Ricaud, C.; Hostettman, K. 1988 Phytochemistry 1994, 27, 3593.
• 6. Zhou, X.H.; Kadsai, K.; Ohtami, O.; Tanaka, O.; Nie, R.; Yang, C.; Zhou, J.; Yamasaki, K. Phytochemistry 1992, 31, 3642.
• 7. Nandy, A.K.; Podder, G.; Sahu, N.P.; Mahato, S.B. Phytochemistry 1989, 28, 2769.
• 8. Bombardelli, E.; Bonati, A.; Gabetta, B.; Mustich, G. Phytochemistry 1974, 13, 2559.

Publication Dates

• Publication in this collection
  23 Oct 2002
• Date of issue
  1999

History

• Received
  07 Aug 1998