Multifidone: A novel cytotoxic lathyrane-type diterpene having an unusual six-membered A ring from Jatropha multifida

Multifidone: A novel cytotoxic lathyrane-type diterpene having an unusual six-membered A ring from Jatropha multifida

Bioorganic & Medicinal Chemistry Letters 19 (2009) 77–79 Contents lists available at ScienceDirect Bioorganic & Medicinal Chemistry Letters journal ...

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Bioorganic & Medicinal Chemistry Letters 19 (2009) 77–79

Contents lists available at ScienceDirect

Bioorganic & Medicinal Chemistry Letters journal homepage: www.elsevier.com/locate/bmcl

Multifidone: A novel cytotoxic lathyrane-type diterpene having an unusual six-membered A ring from Jatropha multifida q Biswanath Das a,*, Kongara Ravinder Reddy a, Bommena Ravikanth a, Tuniki Venugopal Raju b, Balasubramanian Sridhar c, Patan Usman Khan d, Janapala Venkateswara Rao d a

Organic Chemistry Division—I, Indian Institute of Chemical Technology, Hyderabad 500007, India NMR Division, Indian Institute of Chemical Technology, Hyderabad 500007, India c Department of X-ray Crystallography, Indian Institute of Chemical Technology, Hyderabad 500007, India d Biology Division, Indian Institute of Chemical Technology, Hyderabad 500007, India b

a r t i c l e

i n f o

Article history: Received 20 August 2008 Revised 30 October 2008 Accepted 6 November 2008 Available online 9 November 2008

a b s t r a c t Chemical examination of the stems of Jatropha multifida afforded a novel lathyrane-type diterpene, multifidone, having an unusual six-membered A ring. The structure of the compound was determined from detailed analysis of its 1D and 2D NMR spectra and X-ray crystallographic analysis. Its cytotoxicity was measured on four different cancerous cell lines. Ó 2008 Elsevier Ltd. All rights reserved.

Keywords: Jatropha multifida Euphorbiaceae Multifidone X-ray analysis Cytotoxicity

Jatropha multifida Linn (Euphorbiaceae), a shrub of 2–3 m is indigenous to various parts of India.1 The plant is known to posses different medicinal properties including antibiotic activity.2 Earlier investigation on the latex of the plant afforded some cyclic peptides, phenolics, and glucosides.3–5 The peptides were shown to inhibit selectively the classical pathway of human complement activation.3 However, the chemical examination of the other parts of the plant has not yet been reported. In continuation of our work6–8 on the constituents of Jatropha species we recently investigated the stems of J. multifida and isolated a novel diterpene, multifidone.9 The molecular formula C20H26O3 was assigned for the compound from its elemental and mass spectral analyses [m/z 337.1786 [M+Na]+ in HRMS and 337 [M+Na]+ in ESI-MS] and 13C NMR spectrum.10 The structure of the compound was established from detailed analysis of its IR, UV and 1D and 2D NMR spectral (1H–1H COSY, HSQC, HMBC, and NOESY) data. The IR spectrum of the compound showed the presence of carbonyl group, unsaturation and ether linkage while the UV spectrum indicated the presence of a, b-unsaturated carbonyl moiety in the molecule. The 1H and 13C NMR spectral values of 1 (Table q

Part 66 in the series, ‘Studies on novel bioactive phytochemicals’. * Corresponding author. Tel./fax: +91 40 7160512. E-mail address: [email protected] (B. Das).

0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmcl.2008.11.014

1) were compared to those of the reported constituents of Jatropha.6–8,11–13 However, the values were only partially correlated with those of the known lathyrane-type diterpene 2 indicating that the structures of both the compounds were somewhat related.13 In the 1H NMR (400 MHz) spectrum of 1 two singlets for one proton each appeared at d 6.61 (s) and 6.35 (s), which closely resembled the two vinylic protons of 2 suggesting the presence of two trisubstituted double bonds in 1. The spectrum also showed the signals for five methyl groups that resonated at d 2.05 (s), 1.29 (s), 1.06 (d, J = 7.3 Hz), 0.92 (s) and 0.81(s). The other signals at d 0.45 (1H, ddd, J = 9.5, 8.8, 2.5 Hz) and 0.67 (1H, ddd, J = 9.5, 8.8, 2.0 Hz) indicated the presence of cyclopropane ring protons as in 2. The 1H–1H COSY experiment showed the sequence: H-8–H-9– H-10–H-12–H-13–H-14–Me-20 in 1. The 13C NMR spectrum of multifidone showed the presence of 20 non-equivalent carbon atoms. The protonated carbons were assigned from HSQC experiment and characterized by DEPT experiment while the non-protonated carbons were detected by HMBC experiment. The 13C NMR (100 MHz) spectrum in assistance with the above experiments clearly showed the signals for two carbonyls, two disubstituted double bonds, five methyl groups and two oxygenated quaternary carbons (Table 1). The HMBC experiment (Fig. 1) was highly useful to determine the structure of multifidone. This experiment showed the presence of six-membered A ring having two keto groups at C-1

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B. Das et al. / Bioorg. Med. Chem. Lett. 19 (2009) 77–79

Table 1 NMR spectral data of compound 1a Position

1

Multiplicity (J in Hz)

13

1 2 3 4 5 6 7 8 9 10 11 12 13

— 6.61 — — — 6.35 — 1.84–1.98 1.63–1.76 0.45 — 0.67 1.62–1.65 1.36–1.38 2.37–2.39 — 2.05 1.29 0.92 0.81 1.06

— s — — — s — m m ddd (9.5, 8.8, 2.5) — ddd (9.5, 8.8, 2.0) m m m — s s s s d (7.3)

199.8 136.7 150.4 186.2 139.4 140.1 93.6 39.4 20.2 29.9 16.6 22.1 24.9

H NMR

14 15 16 17 18 19 20 a

1

H–1H COSY (selected)

C NMR

38.3 100.2 15.7 29.2 14.2 29.1 14.1

1

HMBC (selected)

NOESY (selected)

C-4, C-15, C-16

H-16

C-4, C-8 C-15, C-17

H-17

H-9 H-8, H-10 H-9, H-12

C-6, C-17 C-7, C-12 C-8, C-13, C-18, C-19

H-12, H-20

H-10, H-13 H-12, H-14

C-14, C-18, C-19 C-10,C-11, C-15

H-13, H-20

C-5, C-12

H-14

C-2, C-4 C-6, C-8 C-10, C-12, C-19 C-10, C-12, C-18 C-13, C-15

H-10, H-20

H-2 H-6

H-10, H-12

13

The spectra were run in CDCl3 at 400 MHz ( H NMR) and 100 MHz ( C NMR).

18 19 20

11

13

O

H 14

2

1 A 4

H

H

14 9

10

1 16

2

7 6

16

O

OH

O

8

13

O

O

10

19 18

14

9

O

15

H 11

8

H

3 7

4

17

17

12

20

12

H

O

O

15

H 20

5

6 17

OH 1

1 Figure 1. Selected HMBC (

2 ) and NOESY correlations (

and C-4, a double bond at C-2, C-3 and a methyl group at C-3. This experiment indicated the correlations of H-2 (d 6.61) with C-4 (d 186.2), C-15 (d 100.2), and C-16 (d 15.7) and those of H-16 (d 2.05) with C-1 (d 199.8), C-2 (d 136.7), and C-4 (Table 1). The HMBC experiment further showed that H-6 (d 6.35) was correlated to C-4, C-15, and C-17 (d 29.2), H-17 (d 1.29) to C-6 (d 140.1) and C-8 (d 39.4), H-9 (d 1.76–1.63) to C-7 (d 93.6) and H-13 (d 1.62–1.65/1.36–1.38) and Me-20 (d 1.06) to C-15. These correlations suggested the presence of a furan ring involving C-5, C-6, C-7, and C-15 with the ether linkage between C-7 and C-15 and a double bond at C-5 (d 139.4), C-6. The (E)configuration of this double bond is evident from the 13C NMR values of the corresponding carbons (C-5, C-6).13 The HMBC spectrum also showed the correlations of Me-18 (d 0.92) and Me-19 (d 0.81) with C-10 (d 29.9) and C-12 (d 22.1) suggesting the presence of cyclopropane moiety at C-10, C-12 with gem-dimethyl groups at C-11 as in 2. The relative stereochemistry of 1 was derived from NOESY correlations (Fig. 1). H-10 (d 0.45) was correlated to H-12 (d 0.67) and H-12 to H-20 (d 1.06) but H-14 (d 2.37–2.39) was not correlated to Me-17 (d 1.29) (Table 1). These correlations suggested that H-10, H-12, H-20, and Me-17 possess a-configuration. The similar relative stereochemistry was also observed in 2 except at Me-17. H-2 also showed NOESY correlations with Me-16 and H-6 with Me-

) of compound 1.

Figure 2. X-ray crystallographic structure of compound 1.

17 showing their proximity. Thus, the structure and stereochemistry of multifidone were clearly established. Finally, the X-ray crystallographic analysis14 confirmed the structure of multifidone (1) (Fig. 2).

B. Das et al. / Bioorg. Med. Chem. Lett. 19 (2009) 77–79

References and notes

Table 2 Cytotoxic activity of multifidone on different cancerous cell lines IC50 (in lM)a

Cell line

THP-1 HL-60 A-375 A-549 a

79

Etoposide

Multifidone

2.16 ± 0.15 1.83 ± 0.20 3.92 ± 0.14 9.51 ± 1.32

45.63 ± 02.16 120.70 ± 17.59 159.05 ± 24.33 127.12 ± 03.11

The values represent the mean ± standard error of four individual observations.

The structure of multifidone (1) is interesting as it contains a six-membered A ring in contrast to a cyclopentane ring found occasionally in lathyrane diterpenes of Jatropha species.8,13 Multifidone (1) was tested for in vitro cytotoxic activity against four different cancerous cell lines, THP-1 (human acute monocytic leukemia), HL-60 (human promyelocytic leukemia), A-375 (human malignant melanoma), and A-549 (human lung carcinoma) using the MTT assay according to the method of Mosmann.15 Etoposide was considered as the positive control. Multifidone showed significant decrease in cell viability in all the test cell lines in a concentration dependent manner. IC50 value was determined with each cell line after four individual observations (Table 2). The cytotoxic activity of multifidone (1) on the cell lines followed the following order: THP-1 > HL-60 > A-549 > A-375. Along with multifidone9 the known compounds 15-epi-(4E)jatrograssidentadione,13 jatrophone,11,16 citlalitrione,17 and cleomiscosin A18 were also isolated from the title plant and they were characterized by comparison of their physical (mp, [a]D25) and spectral (1H NMR and MS) data to those reported in the literature. The occurrence of all these known compounds in J. multifida is reported here for the first time. Acknowledgments The authors thank CSIR and UGC, New Delhi for financial assistance. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.bmcl.2008.11.014.

1. Chopra, R. N.; Badhwar, R. L.; Ghosh, S. Poisonous Plants of India; ICAR: New Delhi, 1965. Vol. II, p 792. 2. Aiylaagbe, O. O. Fitoterapia 2001, 72, 544. 3. Kosasi, S.; Van der sluis, W. G.; Boelens, R.; ’t Hart, L. A.; Labadie, R. P. FEBS Lett. 1989, 256, 91. 4. Kosasi, S.; Van der sluis, W. G.; Labadie, R. P. Phytochemistry 1989, 28, 2439. 5. Van den Berg, A. J. J.; Horsten, S. F. A. J.; Van den Bosch, J. J. K.; Kroes, B. H.; Labadie, R. P. Phytochemistry 1995, 40, 597. 6. Ravindranath, N.; Venkataiah, B.; Ramesh, C.; Jayaprakash, P.; Das, B. Chem. Pharm. Bull. 2003, 51, 870. 7. Ravindranath, N.; Reddy, M. R.; Mahender, G.; Ramu, R.; Ravi Kumar, K.; Das, B. Phytochemistry 2004, 65, 2387. 8. Ravindranath, N.; Reddy, M. R.; Ramesh, C.; Ramu, R.; Prabhaker, A.; Jagadeesh, B.; Das, B. Chem. Pharm. Bull. 2004, 52, 608. 9. Isolation of multifidone: The stems of J. multifida were collected from Botanical Garden, Osmania University, Hyderabad, Andhra Pradesh in August 2006 and botanically identified. A voucher specimen (No. 561112) is preserved in IICT herbarium. The shade dried plant material (4 kg) was powdered and extracted three times (72 h in each case) with a mixture of CHCl3 and MeOH (1:1, 4 L) at room temperature. The total extract was concentrated to afford a brownish mass (102.5 g). The residue (using 102 g from the total mass) was subjected to column chromatography over silica. The column was eluted with mixtures of hexane and EtOAc. The following compounds were obtained according to the increasing order of polarity: jatrophone (21 mg), citlalitrione (13 mg), multifidone (9 mg), 15-epi-(4E)-jatrograssidentadione (30 mg), and cleomiscosin A (23 mg). 10. Multifidone (1): Green crystals (hexane–EtOAc, 9:1), mp 255 °C, [a]D25 21.9 (c = 0.002, CHCl3); IR (KBr): 1704, 1677, 1644, 1211 cm 1; UV (MeOH)(log e): 242 (2.1), 213 (2.0) nm; 1H and 13C NMR (CDCl3): Table 1; HRMS Calcd for C20H26O3Na: 337.1779. Found: 337.1786; ESI-MS: m/z 337 [M+Na]+; Anal. Calcd for C20H26O3: C, 76.43; H, 8.28%. Found: C, 76.02; H, 8.53%. 11. Taylor, M. D.; Smith, A. B., III; Furst, G. T.; Gunasekara, S. P.; Bevelle, C. A.; Cordell, G. A.; Fransworth, N. R.; Kupchan, S. M.; Uchida, H.; Branfman, A. R.; Dailey, R. G., Jr.; Sneden, A. T. J. Am. Chem. Soc. 1983, 105, 3177. 12. Jakupovic, J.; Grenz, M.; Schmeda-Hairschmann, G. Phytochemistry 1988, 27, 2997. 13. Schmeda-Hairschmann, G.; Tsichritzis, F.; Jakupovic, J. Phytochemistry 1992, 31, 1731. 14. X-ray crystallographic analysis of 1: Crystal data: C20H26O3, M = 314.41, monoclinic, space group P21, a = 10.2960(11) Å, b = 11.6120(13) Å, c = 15.2267(17) Å, b = 90.871(2), V = 1820.3(3) Å3, Z = 4, Dcalcd = 1.147 mg m 3, T = 294(2) K, l = 0.076 mm 1, F(000) = 680, k = 0.71073 Å. Data collection yielded 13,252 reflection resulting in 3379 unique, averaged reflection, 3134 with I > 2r(I). Full-matrix least-squares refinement led to a final R = 0.0338, wR = 0.0911, and GOF = 0.969. Intensity data were measured on Bruker Smart Apex with CCD area detector. The X-ray data have been deposited in the Cambridge Crystallographic Data Centre (No. CCDC 687266). 15. Mosmann, T. J. Immunol. Methods 1983, 65, 55. 16. Kupchan, S. M.; Sigel, C. W.; Matz, M. J.; Renauld, J. A. S.; Haltiwanger, R. C.; Bryan, R. F. J. Am. Chem. Soc. 1970, 92, 4476. 17. Villarreal, A. M.; Dominguez, X. A.; Williams, H. J.; Scott, A. I.; Reibenspies, J. J. Nat. Prod. 1988, 51, 749. 18. Ray, A. B.; Chattopadhyay, S. K.; Konno, C.; Hikino, H. Tetrahedron Lett. 1980, 21, 4477.