New ceramides from the flower of Albizia julibrissin

Jian Kang, Chang Hong Huo, Zhe Li, Zuo Ping Li *

Department of Natural Medicine Chemistry, Hebei Medical University, Shijiazhuang 050017, China

Received 17 October 2006

Abstract

A new ceramide and its glycoside were isolated from the flower of Albizia julibrissin. Their structures were established as

(2S,3S,4R,8E)-2-[(20R)–hydroxyhexadecanoylamino]-8-tetra-cosene-1,3,4-triol (I) and 1-O-b-D-glucopyranosyl-(2S,3S,4R,8E)-2-

[(20R)-hydroxy-hexade-canoylamino]-8-tetracosene-1,3,4-triol (II) on the basis of chemical and spectroscopic studies.

# 2007 Zuo Ping Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Keywords: Albizia julibrissin Durazz; Ceramide; Cerebroside

The flower of Albizia Julibrissin Durazz (Leguminosae) have been commonly used to treat anxiety, depression and

insomnia in traditional Chinese medicine. The pharmacology experimental results in the forced swimming test and the

tail suspension test with mice showed that the water extract of the flower of A. Julibrissin exhibited obvious

antidepression effect [1,2]. We have been isolated flavonoids and steroids from the flower of A. Julibrissin [3]. As our

ongoing investigation of bioactive compounds from the flower of A. Julibrissin, we isolated a new ceramide and its

glycoside from petroleum ether-soluble fraction of a EtOH extract of this plant. This paper reports the isolation and

characterization of these two new compounds.

1. Experimental

Air dried flower of Albizzia julibrission was purchased at Lerentang Drug Store, Shijiazhuang, Hebei Province and

was identified as the flower of A. julibrission by Professor Fengzhi Nie, Hebei Medical University. A voucher

specimen (No. NMC-2003-1) is deposited in the herbarium of the school of Pharmaceutical Sciences, Hebei Medical

University.

The air dried flower of A. julibrission (5.0 kg) was extracted with 95% EtOH. After evaporation of the solvent

under reduced pressure, the residue (846 g) was suspended in water and extracted with petroleum ether, ether, ethyl

acetate and n-BuOH, successively. The petroleum ether extract (34 g) was subjected to silica gel column

chromatography using petroleum ether–EtOAc (12:1! 7:3), EtOAc, MeOH, respectively. The methanol elution

(5.9 g) was further separated on silica gel column to give nine fractions (Fr 1–9, CHCl2:MeOH = 12:1). Fr 2 was

recrystallized from MeOH to give compound 1 (45 mg). Fr 5 was recrystallized from MeOH to give compound 2(14.8 mg).

www.elsevier.com/locate/cclet

Chinese Chemical Letters 18 (2007) 181–184

* Corresponding author.

E-mail address: zuoping_li@163.com (Z.P. Li).

1001-8417/$ – see front matter # 2007 Zuo Ping Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

doi:10.1016/j.cclet.2006.12.042

2. Results and discussion

Compound 1 (Fig. 1) was isolated as a white amorphous powder, mp 141–142 8C. The molecular composition of 1,

C40H79NO5, was established from combined analysis of HR-FABMS at m/z 654.60365 [M + 1]+ and 13C NMR

spectrum. The 1H and 13C NMR spectral data of 1 are summarized in Table 1.

J. Kang et al. / Chinese Chemical Letters 18 (2007) 181–184182

Fig. 1. The structures of compounds 1 and 2.

Table 11H and 13C NMR spectral data of compounds 1 and 2

No. Compounds 1 Compounds 2

dH (J, Hz) dC HMBC dH (J, Hz) dC

1 4.51 (dd, 4.5, 10.5),

4.41 (dd, 4.5, 10.5)

62.0 2, 3 4.71 (dd, 4.5, 10.5),

4.35 (dd, 4.5, 10.5)

71.2

2 5.11 (m) 53.0 1, 3 5.29 (m) 50.6

3 4.33 (m) 76.8 1, 2, 4, 5 4.28 (t) 74.7

4 4.29 (m) 72.9 2, 3, 6 4.20 (m) 71.2

5 1.96 (m) 33.8 3, 7 30.9

6 1.77 (m) 26.7 24.7

7 2.15 (m) 33.0 2.16 (m) 32.7

8 5.46 (dt, 15.5, 6) 130.7 6, 10 5.50 (m) 129.7

9 5.54 (dt, 15.5, 6) 130.8 7, 11 5.50 (m) 129.5

10 2.05 (m) 33.3 8, 9 2.01 (m) 32.1

11–21 1.24–1.33(m) 28.6–29.1 1.21–1.32 (m) 28.9–28.4

22 31.3 32.8

23 22.9 21.8

24 0.84 (t, 7.0) 14.3 0.84 (t, 6.5) 13.1

NH 8.57 (d, 9.0) C-10, C-2 8.56 (d, 9.0)

10 175.2 174.5

20 4.61 (dd, 3.5, 7.5) 72.4 C-10, C-30, C-40 4.53 (m) 70.3

30 2.22 (m), 2.00 (m) 35.7 C-40 34.4

40 1.74 (m) 25.8 C-20, C-30, C-60 25.5

50–130 22.9–32.1 1.21–1.32 (m) 28.3–28.8

140 31.3 24.7

150 22.1 21.8

160 0.84 (t, 7.0 Hz) 14.3 C-150 0.84 (t, 7.0 Hz) 13.1

Glu-100 4.95 (8.5 Hz) 104.4

200 4.05 (brs) 74.0

300 4.19 (m) 77.3

400 4.19 (m) 69.3

500 3.86 (m) 77.4

600 4.32 (dd), 4.46 (dd) 61.4

The IR spectrum of 1 showed typical absorption bands for hydroxyl, amide and (CH2)n functionalities, and

suggesting the presence of a sphingosine strcture. The NMR data of 1 indicated the presence of an amide linkage (dH

8.57, d, 1H, J = 9.0 Hz, N–H, dC 175.2), an double bond (dH 5.46 and 5.54, dt, each 1H, J = 6.0, 15.5 Hz), and two

long-chain aliphatic moieties. Methanolysis of 1 yielded a fatty acid methyl ester and a long-chain base. The fatty acid

methylester was identified as methyl-2-hydroxypalmitate by means of GC/MS analysis, which was further confirmed

by the fragment ion at 437 [M � H2O–C14H29–H]+ in EI-MS.

The presence of a 1,3,4-trihydroxy unsaturated C24 long-chain base (LCB) was deduced from the 1H–1H COSYand

MS data. The signal at dH 8.57 gave a cross-peak with the signal at dH 5.11 (H-2) in the 1H–1H COSY spectrum of 1,

which, in turn, showed cross-peaks with methylene protons (H-1) at d 4.51 and 4.41 and d 4.33 (H-3). The latter

correlated with the signal at dH 4.29 (H-4). The positive FAB-MS spectrum of 1 showed two pseudomolecular ion

peaks at m/z 676 [M + Na]+ and 654 [M + H]+, respectively. In the EI-MS, the molecular ion peak of LCB at m/z 398

[M � C16H31O2]+, fragment ions at 356 [M � H2O–C20H39]+, 338 [M � 2H2O–C20H39]+ supported that the LCB

moiety possessed 24 carbons, containing a double bond. A careful analysis of the HMBC and 1H–1H COSY spectra

enabled us to determine the double bond in the LCB residue at C-8 (Fig. 2), which could be further confirmed by the

intense fragment ion at m/z 437 [M � H2O–C14H29–H]+, and the fragment ions at 384 [M � C18H35–H2O]+, 201

[398 � C14H29]+, 147 [398 � C18H35]+, 129 [398 � C18H35–H2O]+, and 111 [398 � C18H35–2H2O]+ in EI-MS.

Furthermore, comparison of the spectroscopic data of 1 with those described for the ceramide isolated from Linaria

vulgaris supported that the double bond in the LCB of 1 had the same position at C-8 [4]. The trans (E) configuration of

the double bond was evidenced by the large vicinal coupling constant (dH 15.5 Hz) as well as by the chemical shifts (dC

33.0, C-7; 33.3, C-10) of the methylene carbon adjacent to the olefinic carbon, which was observed at d-27 in (Z)

isomers and at d-33 in (E) isomers [5].

The chemical shift of H-2 signal and the 13C chemical shifts of C-1–C-4, C-10 and C-20 of sphingosine are especially

suitable for the determination of the absolute stereochemistry of the phytosphingosine moiety [6]. The chemical shift

of H-2 (dH 5.11) and the carbon chemical shifts at dC 62.0 (C-1), 53.0 (C-2), 76.8 (C-3), 72.9 (C-4), 175.2 (C-10) and

72.4 (C-20) in 1 were virtually identical with those of the reported data of other (2S,3S,4R,20R)-phytosphingosine

moieties. In conclusion, compound 1 was assigned as (2S,3S,4R,8E)-2-[(20R)-hydroxyhexadecanoyl-amino]-8-

tetracosene-1,3,4-triol.

Compound 2 was isolated as a white amorphous powder, mp 207–208 8C. The NMR spectral data of 2 were

summarized in Table 1 and suggested that compound 2 was a glycosphingolipid. Acid hydrolysis of 2 gave D-glucose,

which was identified by thin-layer chromatography with an authentic sample. The signals at dC 104.4, 74.0, 77.3, 69.3,

77.4 and 61.4 in the 13C NMR spectrum and the signal at dH 4.95 (d, 1H, J = 8.5 Hz) in the 1H NMR suggested the

presence of b-D-glucose [7]. The length of the LCB and the FA of compound 2 were determined by EI-MS, FAB-MS

and methanolysis. The fatty acid methyl ester was identified as methyl-2-hydroxypalmitate by means of GC/MS

analysis, identical with compound 1, which could be further supported by the fragment ion at m/z 437 [M � H2O–

C14H29–H]+ in EI-MS. The FAB-MS of compound 2 showed a pseudomolecular ion peak at m/z 838 [M + Na]+. The

positive EI-MS spectrum showed fragment at m/z 635, indicating the loss of a glucose. The fragment ions at m/z 356

[M � H2O–C20H39]+, 338 [M � 2H2O–C20H39]+, which was identical with that of compound 1, suggesting that the

LCB of compound 2 possessed 24 carbons, containing one double bond, too. The double bond was confirmed at C-8 by

J. Kang et al. / Chinese Chemical Letters 18 (2007) 181–184 183

Fig. 2. The key HMBC correlations of compound 1.

HMBC and 1H–1H COSYexperiment, which was suggested to be trans configuration by the chemical shifts of C-7 (dC

32.7) and C-10 (dC 32.1) [5]. The chemical shift of C-1 (d 71.2) indicated that the glucose moiety was attached to the C-

1 of the compound 2. Thus the compound 2 was identified the glucoside of compound 1.

The stereochemistry compound 2 was established on the basis of the carbon chemical shifts at dC 71.2 (C-1), 50.6

(C-2), 74.7 (C-3), 71.2 (C-4), 174.5 (C-10), 70.3 (C-20) and the proton chemical shift at d 5.29 (H-2), which was fairly

close to those previously reported for (2S,3S,4R,20R) sphingosine moieties [6]. Therefore, compound 2 was assigned as

1-O-b-D-glucopyranosyl-(2S,3S,4R,8E)-2-[(20R)-hydroxyhexa-decanoylamino]-8-tetracosene-1,3,4-triol.

Acknowledgment

We are grateful to the Natural Science Foundation of Hebei Province (No. 3034701) for financial support.

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