.Mollisside A (1) was isolated as white powder. Its molecular formula was determined to be C26H44O8 with five unsaturation degrees by HRFABMS (m/z 483.2959 [M-1]-) and 13C NMR spectra. The 1H NMR spectrum of compound 1 clearly showed signals to three methyls at δ 0.83 (3H, s), 1.03 (3H, s), 1.07 (3H, s), and one anomeric hydrogen of β-type sugar at δ 4.30 (1H, d, J 7.8 Hz). The 13C NMR ({1H} and DEPT) spectroscopic data (Table 1) revealed the presence of 3 methyls, 10 methylenes, 9 methines and 4 quaternary carbons. Carbon signals at δ 106.8 (d), 75.6 (d), 77.7 (d), 71.6 (d), 78.2 (d), 62.8 (t) suggested the presence of one glucose, which were further confirmed by its MS fragmentation peaks at m/z 323 [M-1-160 = C6H8O5 formed by fragmentation involving glc moiety C6H10O5]- and the acid hydrolysis of 1. Comparison of these NMR data with those similar data reported in the literature13 showed that compound 1 had the same ent-kaurane skeleton. The linkage of glucose moiety to C-3 was determined by the HMBC correlations from H-1' (δ 4.30), H-18 (δ 1.03) and H-19 (δ 0.83) to C-3 (δ 90.9) (Figure 2). The attachment of one hydroxyl at C-17 in 1 was established by HMQC and HMBC spectra revealing correlations of H-17 (δ 3.27) with C-16 (δ 80.7), C-13 (δ 42.3) and C-15 (δ 53.1). Besides, the relative configuration of 1 was elucidated by a ROESY experiment and by comparison of the NMR data with those reported in the literature.14 The key ROESY correlations of H-3/H-18, H-3/H-5 and H-9/H-5 (Figure 3), indicated α-orientation of C-3 glycoside and β-orientations of H-5 and H-9. The α-orientation of CH2OH-17 (δc 70.6) in 1 was elucidated by comparison of the 13C NMR data with those reported δc 69.8 for α-orientation and δc 66.2 for β-orientation at C-17.14 Based on the above evidences, compound 1 was identified as 3α, 16β, 17-trihydroxy-ent-kaurane 3-O-β-D- glucopyranoside, named Mollisside A.
Mollisside B (2) was determined to have a molecular formula C26H40O9 on the basis of the positive HRFABMS (m/z 519.2565 [M+Na]+) and 13C NMR (DEPT) spectra, which possessed seven unsaturation degrees. Its IR spectrum showed a broad band (3518-2930 cm-1) and absorption 1691 cm-1 for a carboxyl and 1607 cm-1 for a double bond. The 1H NMR spectrum of compound 2 exhibited three methyls at δ 0.88 (3H, s), 1.12 (3H, s), 1.16 (3H, s), one anomeric proton of β-type sugar at δ 4.32 (1H, d, J 7.8 Hz) and one olefinic proton at δ 6.48 (1H, s). The 13C NMR spectroscopic data (Table 1) revealed 26 carbon atoms, including one carboxyl (C-17 at δ 164.1) and two olefinic carbons (C-16 at δ 139.9, C-15 at δ 154.7). Comparison of these NMR data with mollisside A showed that compound 2 had the similar skeleton of compound 1 except for the distinct differences of chemical shift of C-2 (δ 68.1) adjacent one oxygenated group and C-17, C-15 and C-16 conforming the α,β-unsaturation ketone system. The linkage of the glucose moietiy to C-3 (δ 96.1) was determined by the HMBC correlations from H-1' (δ 4.32), H-18 (δ 1.12) and H-19 (δ 0.88) to C-3 (Figure 2). Besides, the relative configuration of 2 was elucidated by a ROESY experiment and by comparison of the NMR data with 1. The α-orientation of H-2 was established by key ROESY correlations of H-2/H-1α, H-2/H-19 and H-2/H-20 (Figure 3) and the coupling constant J 9.3 Hz observed in the signal corresponding to H-3 (interaction axial- axial with H-2). Moreover, the β-orientations of H-3, H-5 and H-9 were confirmed by ROESY between H-3/H-5, H-3/H-18 and H-5/H-9. Based on the above evidences, the structure of 2 was elucidated as 2β,3α-dihydroxy-ent-kaur-15-en-17-oic acid 3-O-β-D-glucopyranoside, named Mollisside B.
Mollisside A
White powder, mp 292-294 ºC; [α]D21 +6.3116 (c 0.101, CH3OH); UV (CH3OH) λmax/nm (log ε): 193(3.587), 205 (3.829), 277 (3.250); IR (KBr) νmax/cm-1: 3420, 2937, 1166, 1074, 1020; 1H NMR (400 MHz, CD3OD) and 13C NMR (100 MHz, CD3OD) see Table 1; HRESIMS (negative ion) m/z 483.2959 [M-1]- (Calc. for C26H44O8, 483.2957); FABMS (negative ion) m/z(%) 483[M-1]- (100), 391 (5), 323 (15), 282 (5), 159 (6), 113 (5).
Mollisside B
White powder, mp 270-271 ºC; [α]D21 -1.5989 (c 0.246, CH3OH); UV (CH3OH) λmax/nm (log ε): 196 (3.393), 203 (4.108), 276 (2.890); IR (KBr) νmax/cm-1: 3518, 3380, 3190, 2980, 2930, 1691, 1607, 1073, 1037; 1H NMR (500 MHz, CD3OD) and 13C NMR (125 MHz, CD3OD) see Table 1; HRESIMS (positive ion) m/z 519.2565 [M+Na]+ (Calc. for C26H40O9Na, 519.2570); FABMS (negative ion) m/z(%): 495[M-1]- (100), 400 (5), 335 (5), 281(6), 123 (4).
ABSTRACT
Two new kaurane diterpenoids, 3α, 16β, 17-trihydroxy-ent-kaurane 3-O-β-D-glucopyranoside and 2β,3α-dihydroxy-ent-kaur-15-en-17-oic acid 3-O-β-D-glucopyranoside, were isolated from the bark of Albizia mollis (Wall.) Boiv. The structures of two new compounds were elucidated by extensive 1D- and 2D-NMR spectroscopic methods in combination with MS experiments.
Journal of the Brazilian Chemical Society
Print version ISSN 0103-5053
J. Braz. Chem. Soc. vol.21 no.9 São Paulo 2010
http://dx.doi.org/10.1590/S0103-50532010000900025
Two new ent-kaurane diterpenoids from Albizia mollis (Wall.) Boiv
Zhong-Quan ChengI,II; Dan YangI; Yu-Qing LiuI; Jiang-Miao HuI; He-Zhong JiangI; Peng-Cheng WangI; Ning LiIII; Jun ZhouI; You-Xing ZhaoI,*
IState Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming 650204, P. R. China
IIGraduate School of the Chinese Academy of Sciences, Beijing 100049, P. R. China
IIISchool of Life Sciences, Anhui University, Hefei 230039, P. R. China
Keywords: Albizia mollis, kaurane diterpenoids, mollisside A, mollisside B
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