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Chemistry of Natural Compounds

, Volume 48, Issue 4, pp 583–586 | Cite as

seco-Kaurane skeleton diterpenoids from Croton oblongifolius

  • Sunisa Suwancharoen
  • Orawan Chonvanich
  • Sophon Roengsumran
  • Surachai Pornpakakul
Article

A new seco-kaurane type diterpenoid, ent-3,4-seco-17-oxo-kaur-4(19),15(16)-dien-3-oic acid, and a known compound, ent-3,4-seco-kaur-4(19),16(17)-dien-3-oic acid, were isolated from the stem bark of Croton oblongifolius. The structures of these compounds were established on the basis of spectroscopic data.

Keywords

Croton oblongifolius diterpenoid seco-kaurane 

Croton oblongifolius Roxb. (Euphorbiaceae) is widely distributed in Thailand and has been used as a medicinal plant for the treatment of dysmenorrhea, as a purgative, and to treat dyspepsia and dysenteria. This plant has also been used in conjunction with C. sublyratus to treat gastric ulcers and gastric cancers. The chemical constituents of Croton oblongifolius Roxb. were first reported by Seshadri et al. during 1968 to 1972 [1, 2, 3, 4, 5]. Due to the interest in the identification of biologically active compounds of this plant, we have investigated this plant in Thailand and found that it contains different chemical constituents. In a decade of our continuing investigation on the chemical constituents of C. oblongifolius in various parts of Thailand, we found that this plant is a rich source of diterpenoid compounds with various skeletons [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18]. As part of our continuing search for novel diterpenoids in this plant, we investigated the chemical constituents of this plant by comparing its 1H NMR profile in hexane extracts with the 1H NMR data of our previous reported compounds. We found a new 3,4-seco-kaurane-type diterpenoid, ent-3,4-seco-17-oxo-kaur-4(19),15(16)-dien-3-oic acid (2), together with a known diterpenoid, ent-3,4-seco-kaur-4(19),16(17)-dien-3-oic acid (1). In this paper we describe the isolation and structure elucidation of 1 and 2.

In comparison with the 1H NMR data of our previous report, the 1H NMR profile of the hexane extract of C. oblongifolius specimens collected from Amphoe Nong-Han, Udon-Thani Province, in the northeastern part of Thailand displayed mainly one compound that was similar to that of ent-kaur-16-en-19-oic acid. After isolation using silica gel column chromatography eluted with hexane–ethyl acetate in a stepwise fashion, compound 1 was obtained as a major component along with compound 2.

The molecular formula of compound 1 was assigned as C20H30O2 based on high-resolution mass spectrometric analysis, which exhibited an [M + H]+ ion at m/z 303.2319. 1H and 13C NMR (Table 1) indicated the presence of two methyl carbons, eight sp 3-methylene carbons, two sp 2-methylene carbons, three sp 3-methine carbons, two sp 3-quaternary carbons, two sp 2-quaternary carbons, and a carbonyl carbon. Since the six degrees of unsaturation have been accounted for, we assume that 1 contains three rings. From the HMBC data (Table 1) with the assistance of COSY, TOCSY, and NOESY (Fig. 1), 1 was identified as ent-3,4-seco-kaur-4(19),16(17)-dien-3-oic acid. A search through the crossfire Beilstein database revealed that compound 1 was the known compound reported in [19]. A comparison of the specific optical rotation {[α] D 20 –45° (c 0.28, CHCl3)} of 1 with that reported in the crossfire Beilstein database {[α] D 20 –33° (c 0.28, CHCl3)} indicated that compound 1 is the same compound.
Table 1

1D and 2D NMR Data of 1 and 2 a (J/Hz)

C atom

1

2

δC

δH

HMBC (H → C)

δC

δH

HMBC (H → C)

1

33.6

1.65 m

3, 5

33.6

1.71 m

2, 3, 9, 10

  

1.70 m

  

1.73 m

 

2

28.5

2.15 (ddd, J = 7.4, 11.6, 16)

1, 3

28.2

2.14 (ddd, J = 6.4, 11.6, 16)

1, 3

  

2.31 (ddd, J = 5.2, 12.8, 16)

1, 3

 

2.33 (ddd, J = 6, 10.8, 16)

1, 3

3

180.0

 

178.1

 

4

147.4

 

146.9

 

5

50.4

1.97 (dd, J = 2, 9)

4, 10, 18, 19, 20

50.1

2.00 (br.d, J = 11.2)

 

6

26.2

1.43 m

 

36.6

1.70 m

8, 10

  

1.41 m

  

1.66 m

8, 10

7

39.5

1.41–1.51 mb

8

24.7

1.48 m

 
     

1.56 m

 

8

43.9

 

50.5

 

9

46.0

1.20 (br.d, J = 6.8)

1, 8, 10, 11, 12, 20

37.3

1.25 (br.d, J = 7.6)

1, 8, 10, 11, 12, 14, 15, 20

10

40.8

 

41.1

 

11

18.2

1.49 m

8, 13

18.5

1.52–1.55 mb

 
  

1.64 m

    

12

32.9

1.50 m

 

24.9

1.54–1.62 mb

 
  

1.63 m

    

13

43.7

2.65 br.s

8

37.8

3.07 br.s

 

14

39.4

1.95 (d, J = 10.4)

8, 12, 13, 15, 16

42.9

2.15 (d, J = 10.8)

7, 15, 16

15

49.0

1.15 (dd, J = 4, 10.4) 2.01–2.13 mb

7, 8, 9, 12, 13 8, 9, 16, 17

161.1

1.53 m 6.59 s

8, 12 8, 13, 14, 16, 17

16

155.3

 

148.6

 

17

103.2

4.80 s

13, 15

189.4

9.74 s

13, 16

  

4.74 s

13, 15

   

18

23.3

1.73 sc

4, 5, 19

23.2

1.74 sc

4, 5, 19

19

113.6

4.87 s

5, 18

114.0

4.89 s

5, 18

  

4.64 s

5, 18

 

4.67 s

5, 18

20

21.8

1.00 sc

1, 5, 9, 10

21.7

1.06 sc

1, 5, 9, 10

aData were obtained at 400 MHz for 1H and 100 MHz for 13C NMR with chemical shifts (δ) in ppm and were referenced to residual solvent signals with resonances at δH 7.26 and at δC 77.0. bIntensity of two protons; cintensity of three protons.

Fig. 1

COSY, TOCSY, and NOESY correlations of 1 and 2.

The molecular formula of compound 2 was assigned as C20H28O3 based on high-resolution mass spectrometric analysis, which exhibited an [M + Na]+ ion at m/z 339.1941. The 1H NMR spectrum of 2 showed a sharp singlet signal of an aldehyde proton at δ 9.74. The presence of the aldehyde functional group was also supported by the 13C NMR spectrum, which showed a signal at δ 189.4. The 1H and 13C NMR data of 2 (Table 1) are similar to those of 1 except that compound 2 has an aldehyde function (δH 9.74 and δC 189.4) at C-17. 1H and 13C NMR (Table 1) indicated the presence of two methyl carbons, seven sp 3-methylene carbons, one sp 2-methylene carbon, three sp 3-methine carbons, two sp 3-quaternary carbons, one sp 2-methine carbon, two sp 2-quaternary carbons, and two carbonyl carbons. Since the seven degrees of unsaturation have been accounted for, we assume that 2 contains three rings. The HMBC analysis (Table 1) with the assistance of COSY, TOCSY, and NOESY (Fig. 1) led to the structure of 2. The relative stereochemistry at C-5, C-8, C-9, and C-10 were assigned on the basis of the cross-peaks observed between H-9 and H-1, between H-9 and H-2, between H-9 and H-5, between H-9 and H-15, and between the methyl protons of C-18 and the methyl protons of C-20 in the NOESY analysis. Thus, compound 2 was identified as a novel compound. The absolute configuration of 2 was tentatively assumed to have the same ent configuration of ent-kaur-16-en-19-oic acid [15] due to close similarity of their structures and based on their negative optical rotation sign.

Experimental

General Experimental Procedures. 1H and 13C NMR spectra were recorded on a Varian Mercury +400 MHz NMR spectrometer (1H at 400 MHz and 13C at 100 MHz). Chloroform-d (CDCl3) was used in NMR experiments and chemical shifts (δ) were referenced to the signals of residual solvents at 0 7.26 ppm (1H) and 77.0 ppm (13C). HR-ESI-MS spectra were recorded on Micromass LCT (LC/MS). Optical rotations were measured on a Perkin–Elmer 341 polarimeter using a sodium lamp at wavelength 589 nm. FT-IR spectra were recorded on a Perkin–Elmer model 1760X Fourier transform infrared spectrophotometer. Melting points were examined using a Fisher-John melting point apparatus. All solvents used for column chromatography were of commercial grade and were distilled prior to use. TLC were carried out on precoated silica gel 60 F254 (Merck), and spots were detected under UV (254 and 365 nm) before and after spraying with a vanillin/sulfuric acid solution followed by heating the plate. Isolations were carried out using column chromatography (CC) [silica gel 60 (Merck, 0.040–0.063 mm)].

Plant Material. The stem bark of C. oblongifolius was collected from Amphoe Nong-Han, Udon-Thani Province, Thailand. Botanical identification was achieved through comparison with a voucher specimen No. BKF 084729 in the Herbarium collection of the Royal Forest Department of Thailand.

Extraction and Isolation of 1 and 2. The powdered, sun-dried stem bark (12.8 g) of C. oblongifolius was extracted with hexane (5 × 500 mL). The hexane extract was filtered and evaporated in vacuo to obtain a viscous greenish yellow residue (125 mg). The hexane extract (120 mg) was fractionated by silica gel column chromatography and eluted with hexane–EtOAc in a stepwise fashion. Similar fractions were combined on the basis of TLC with detection by UV light and vanillin–H2SO4 reagent. Fractions 10–15, eluted with 5% ethyl acetate in hexane, were further purified by silica gel column chromatography eluting with 5% ethyl acetate in hexane to afford compound 1 as a clear film (20 mg). Fraction 17–20, eluted by 10% ethyl acetate in hexane, was further purified by silica gel column chromatography eluting with 10% ethyl acetate in hexane to afford compound 2 as a clear film (3 mg).

ent- 3,4- seco- Kaur-4(19),16(17)-dien-3-oic Acid (1). [α] D 20 neat, cm–1): 3400 br, –45° (c 0.28, CHCl3). IR (νmax, 1698, and 1637. 1H NMR (400 MHz, CDCl3), see Table 1; 13C NMR (100 MHz, CDCl3), see Table 1. HR-ESI-MS m/z 303.2319 ([M + H]+ calcd for C20H30O2 + H, 303.2324).

ent -3,4- seco -17-Oxo-kaur-4(19),15(16)-dien-3-oic Acid (2). [α] D 20 neat, cm–1): –54° (c 0.03, MeOH). IR (νmax, 3400 br, 2705, 1699, 1690, and 1638. 1H NMR (400 MHz, CDCl3), see Table 1; 13C NMR (100 MHz, CDCl3), see Table 1. HR-ESI-MS m/z 339.1941 ([M + Na]+ calcd for C20H28O3Na, 339.1936).

Notes

Acknowledgment

We thank the National Research University Project of CHE, the Ratchadaphiseksomphot Endowment Fund (FW1022B), and the Higher Education Commission Grants for Graduate Dissertation, Chulalongkorn University, for financial support. The Department of Chemistry, Faculty of Science, and the Rachadapiseksompoj Endowment, Chulalongkorn University, are also gratefully acknowledged.

References

  1. 1.
    P. S. Rao, G. P. Sachdev, T. R. Seshadri, and H. B. Singh, Tetrahedron Lett., 9, 4685 (1968).CrossRefGoogle Scholar
  2. 2.
    V. N. Aiyar and T. R. Seshadri, Tetrahedron, 26, 5275 (1970).CrossRefGoogle Scholar
  3. 3.
    V. N. Aiyar and T. R. Seshadri, Indian J. Chem., 9, 1028 (1971).Google Scholar
  4. 4.
    V. N. Aiyar and T. R. Seshadri, Phytochemistry, 11, 1473 (1972).CrossRefGoogle Scholar
  5. 5.
    V. N. Aiyar and T. R. Seshadri, Curr. Sci., 41, 839 (1972).Google Scholar
  6. 6.
    S. Roengsumran, S. Achayindee, A. Petsom, K. Pudhom, P. Singtothong, C. Surachetapan, and T. Vilaivan, J. Nat. Prod., 61, 652 (1998).PubMedCrossRefGoogle Scholar
  7. 7.
    S. Roengsumran, P. Singtothong, K. Pudhom, N. Ngamrochanavanich, A. Petsom, and C. Chaichantipyuth, J. Nat. Prod., 62, 1163 (1999).PubMedCrossRefGoogle Scholar
  8. 8.
    K. Pudhom, T. Vilaivan, N. Ngamrojanavanich, S. Dechangvipart, D. Sommit, A. Petsom, and S. Roengsumran, J. Nat. Prod., 70, 659 (2007).PubMedCrossRefGoogle Scholar
  9. 9.
    S. Roengsumran, A. Petsom, D. Sommit, and T. Vilaivan, Phytochemistry, 50, 449 (1999).CrossRefGoogle Scholar
  10. 10.
    S. Roengsumran, A. Petsom, N. Kuptiyanuwat, T. Vilavan, C. Ngamrojnavich, C. Chaichantiyouth, and S. Puthong, Phytochemistry, 56, 103 (2001).PubMedCrossRefGoogle Scholar
  11. 11.
    S. Roengsumran, N. Jaiboon, N. Chaichit, D. Sommit, D. Pattamadilok, C. Chaichantipyuth, and A. Petsom, J. Chem. Crystallogr., 32, 511 (2002).CrossRefGoogle Scholar
  12. 12.
    C. Chaichantipyuth, A. Petsom, P. Taweechotipatr, N. Muangsin, N. Chaichit, S. Puthong, S. Roengsumran, M. Kawahata, T. Watanabe, and T. Ishikawa, Heterocycles, 65, 809 (2005).CrossRefGoogle Scholar
  13. 13.
    S. Roengsumran, K. Musikul, A. Petsom, T. Vilaivan, P. Sangvanich, S. Pornpakakul, S. Puthong, C. Chaichantipyuth, N. Jaiboon, and N. Chaichit, Planta Med., 68, 274 (2002).PubMedCrossRefGoogle Scholar
  14. 14.
    C. Chaichantipyuth, N. Muangsin, N. Chaichit, S. Roengsumran, A. Petsom, T. Watanabe, and T. Ishikawa, Z. Kristallogr. - New Cryst. Struct., 219, 111 (2004).Google Scholar
  15. 15.
    N. Ngamrojnavanich, S. Sirimongkon, S. Roengsumran, A. Petsom, and H. Kamimura, Planta Med., 69, 555 (2003).PubMedCrossRefGoogle Scholar
  16. 16.
    S. Roengsumran, S. Pornpakakul, N. Muangsin, P. Sangvanich, T. Nhujak, P. Sintothong, N. Chaichit, S. Puthong, and A. Petsom, Planta Med., 70, 87 (2004).PubMedCrossRefGoogle Scholar
  17. 17.
    S. Roengsumran, P. Pata, N. Ruengraweewat, J. Tummatorn, S. Pornpakakul, P. Sangvanich, S. Puthong, and A. Petsom, Chem. Nat. Comp., 45, 641 (2009).CrossRefGoogle Scholar
  18. 18.
    S. Suwancharoen, W. Tommeurd, C. Phurat, N. Muangsin, N. Chaichit, and S. Pornpakakul, Acta Crystallogr., E, 66, o1531 (2010).Google Scholar
  19. 19.
    G. Palazzino, E. Federici, P. Rasoanaivo, C. Galeffi, and F. D. Monache, Gazz. Chim. Ital., 127, 311 (1997).Google Scholar

Copyright information

© Springer Science+Business Media, Inc. 2012

Authors and Affiliations

  • Sunisa Suwancharoen
    • 1
  • Orawan Chonvanich
    • 2
  • Sophon Roengsumran
    • 1
  • Surachai Pornpakakul
    • 1
  1. 1.Research Centre for Bioorganic Chemistry, Department of Chemistry, Faculty of ScienceChulalongkorn UniversityBangkokThailand
  2. 2.Program of Biotechnology, Faculty of ScienceChulalongkorn UniversityBangkokThailand

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