Journal of the Chinese Chemical Society, 2008, 55, 401-405 401 Acyclic Diterpene-g-lactones and Flavonoid from Salix cheilophila Omitted Tong Shena* ( ), Yong-Qiang Tiana (), Wu-Xia Liua ( ) and Shang-Zhen Zhengb () aSchool of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070, P. R. China bCollege of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, P. R. China Three new phytane-type diterpene-g-lactone shaliuin I (2), shaliuin II (3) and shaliuin III (4)were isolated along with thirteen known compounds from twigs of Salix cheilophila omitted (Chinese name “Shaliu”, Salicaceae). The structures of three new compounds have been established on the basis of spec- troscopic methods and 2D NMR techniques. Keywords: Salix cheilophila; Salicaceae; Twigs; Acyclic diterpene-g-lactone. INTRODUCTION pyranoside (11),8 luteolin-7-O-b-D-glucopyranoside (12),8 Salix cheilophila omitted is mostly distributed in luteolin-5-O-b-D-glucopyranoside (13),8 stigmast-4-en- Hebei, Shanxi, Qinghai and Gansu Provinces and the north- 3b-ol-6-one (14),9 stigmast-5-en-3b-ol-7-one (15),9 b-sito- west of China. It shows a strong effect as an anti-influenza, sterol (16).10 antipruritic, antirheumatic, and antineoplastic agent among Compound 2 was obtained as a pale yellow gum with 1 a 20 ° others. However, its chemical constituents have not been [ ] D -131.7 (c, 0.26, CHCl3). Its HR-EIMS gave a peak at reported so far. We have carried out a detailed chemical in- m/z 430.2965 corresponding to the molecular formula vestigation and have isolated three new acyclic diterpene- C26H38O5 (calc 430.2972), indicating eight degrees of g-lactones (2, 3 and 4) along with thirteen known com- unsaturation. The IR absorption at 1746, 1682 cm-1 indi- pounds (1, 5-16) from the ethanol extract of the plant. In cated the presence of an a,b-unsaturated-g-lactone; its IR the present article, we report the isolation and structure elu- spectrum also showed bands assigned to ester carbonyl cidation of the three new compounds shaliuin I (2), shaliuin (1718 cm-1), double bond (1652 cm-1) and a hydroxyl group II (3), and shaliuin III (4). (3362 cm-1). 1Hand13C NMR and DEPT spectra (see Ta- bles 1 and 2) of 2 revealed signals due to six methyls, six RESULTS AND DISCUSSION methylenes, seven methines and seven quaternary carbons Sixteen compounds were isolated by repeated col- (five olefinic carbons, two carbonyl), which suggest the umn chromatography on silica gel and preparative TLC presence of 26 carbons. The 1H-1H COSY and HMBC from the ethanol extract of Salix cheilophila. Three new spectra indicated that 2 is an acyclic diterpene composed of compounds, structures were identified as shaliuin I, shaliuin the structural fragments i, ii and iii. In fragment i, the 1H-1H II, and shaliuin III. The known compounds (1, 5-16)were COSY and HMQC spectra strongly indicated the presence identified by comparing their spectral data with those of of an a,b-unsaturated-g-lactone skeleton;11,12 two methyl- authentic samples or with those reported in the literature as enes group, two tri-substituted double bonds, a hydroxyl hanliuin IV (1),2 8b,19-dihydroxy-3-oxopimar-15-ene group and two vinylic methyls group were present, the sig- 3 4 5 (5), feruloyl glucose (6), porusterone I (7), 6,7-dihy- nals at d 3.88 due to C12-OH, and d 73.0 due to C-12, d 4.64 6 droxy-3¢-methoxy-4¢,5¢-methylenedioxyisoflavone (8), (1H, brs, H-12) coupled with the H-9a (d 2.23). The signal 6,7-dihydroxy-3¢-methoxy-4¢,5¢-methylenedioxyisofla- at d 6.90 was ascribed to H-10, which was correlated with 6 7 vone-6-O-b-D-glucopyranoside (9), caffeic acid (10), H-8b (d 2.04), H-9a (d 2.23) and H-9b (d 2.09). The chemi- 5,3¢-dihydroxy-4¢-O-angeloxyflavone-7-O-b-D-gluco- cal shift is in accordance with the a,b-proton of an a,b-un- * Corresponding author. E-mail: [email protected] 402 J. Chin. Chem. Soc., Vol. 55, No. 2, 2008 Shen et al. ment iii showed the vinyl proton at d 5.48 (J = 7.0, 2.0 Hz; H-2; d 124.1, C-2) coupled with H-1 (d 6.36, 2H, J =7.0 Hz; H-1; d 68.0, C-1) and allylically with a methyl group (d 1.59, 3H, H-20; d 23.6, C-20). In addition, its 1HNMRatd 5.66 (tq, H-2¢), 2.17 (dq, H-4¢), 1.08 (t, H-5¢), 2.18 (d, H-6¢) showed the presence of a methylsenecioyloxy group,13 which was also confirmed by the C6H10O2 unit due to the + + fragmentations [M-114 (C6H10O2)] and [C6H10O2-OH] peak at m/z 316and97intheEIMSspectrum.14 Except for the 13C NMR spectrum at d 166.7 (carbonyl, C-1¢), d 115.0 (C-2¢), 163.4 (quaternary, C-3¢), 33.7 (C-4¢), 11.8 (C-5¢), 18.8 (C-6¢) showed the presence of a methylsenecioyloxy group. The HMBC spectrum showed that there were cross peaks of C-1¢ (d 166.7) with H-1 (d 6.36). Thus, the methyl- senecioyloxy group must be attached to C-1. Besides, in the structural fragment ii, the broad triplet at d 5.32 (H-6) ex- hibited a cross peak with partially overlapped multiplets of two methylenes at d 2.10 (H-4) and d 1.90 (H-5), also with the broad singlet of the vinylic methyl group at d 1.45 (H- 19), respectively. The relative stereochemistry of 2 was supported by NOESY correlations, which showed cross peaks of H-1/H-4 and H-2/H-20 establishing the configura- tion of the D2-double bond as 2, and the cross peaks of H-9/H-12 revealed the E-configuration of the D10-double bond, also the E-configuration of the D6-double bond was supported by the NOESY correlation for H-6/H-8b and (d 2.04, brt, J = 11.2) by a chemical shift of C-19 (d 11.3).15,16 Comparison of its NOESY spectrum of 2 with those of structurally related natural products,12 implied that their relative chemistry was the same. But absolute configura- tion at C-8, C-12 and C-13 were not determined, and cou- pling constant J12,13 = 2.0 Hz was in agreement with a di- hedral angle of 70 or 115° which requires a trans-relation- ship of H-12 and H-13,12 thus we concluded that 2 is an acyclic deterpene-g-lactone named shaliuin I. Compound 3 was a pale yellow gum and its HR- EIMS displayed a [M+], at m/z 472.3119 (calc 472.3124) in saturated-g-lactone. This conclusion was supported by the agreement with a molecular formula of C28H40O6, indicat- 13CNMRdata(d 142.2, C-10; d 132.0, C-11; d 170.2, ing nine degrees of unsaturation. In the IR spectrum absorb- C-18). The proton at d 6.90 (H-10) correlated also with a ances for hydroxyl (3359 cm-1), a,b-unsaturated-g-lactone broad singlet at d 4.64 (H-12, d 73.0, C-12). The signal at d (1743, 1684 cm-1), ester carbonyl (1720 cm-1) and double 4.64 was coupled with a double double signal assigned to bond (1654 cm-1) were observed as in 3. the proton (d 5.40, H-13 and d 82.7, C-13), which also cor- The 1Hand13C NMR data (Tables 1 and 2) of 3 were related with a double multiplet of an olefinic proton (d found to be similar to those of 2. This suggested that 3 and 2 4.98, H-14; d 120.4, C-14). This, in turn, was coupled with have a similar skeleton. But 3 featured an additional ace- the broad singlet signals of two vinylic methyls at d 1.74, toxy group (dH 2.08, dC 170.9) at C-8; chemical shifts were (H-16) and d 1.72, (H-17). Furthermore, the structural frag- established by DEPT analysis and HMQC, HMBC. The Studies on Chemical Constituents of Salix cheilophila Schneid J. Chin. Chem. Soc., Vol. 55, No. 2, 2008 403 1 Table 1. H NMR spectral data of compounds 2, 3 and 4 (400 MHz, d in ppm, CDCl3,TMS)* 234 Proton dH J (Hz) dH J (Hz) dH J (Hz) 1(1¢) 6.36 (d, 7.0) 6.32 (d, 7.0) 6.32 (d, 7.0) 2 5.48 (tq, 7.0, 2.0) 5.44 (tq, 7.0, 2.0) 5.46 (tq, 7.0, 2.0) 4 2.10 (tq, 7.0, 1.8) 2.10 (tq, 7.0, 1.8) 2.12 (tq, 7.0, 1.8) 5 1.90 (m) 1.89 (m) 1.90 (m) 6 5.32 (brt, 6.8) 5.29 (brt, 6.8) 5.30 (brt, 6.8) 8a 2.16 (ddd, 11.0, 6.2, 1.8) 4.20 (dd, 11.0, 6.0) 3.98 (dd, 11.0, 6.2) 8b 2.04 (brt, 11.2) 9a 2.23 (m) 2.30 (m) 2.28 (m) 9b 2.08 (m) 2.23 (m) 2.23 (m) 10 6.90 (ddd, 10.2, 6.8, 1.8) 6.89 (ddd, 10.2, 6.8, 1.9) 6.89 (ddd, 10.2, 6.8, 1.9) 12 4.64 (d, 2.0) 4.67 (brs) 4.69 (brs) 13 5.40 (brs) 5.40 (brs) 5.46 (brs) 14 4.98 (brs) 4.98 (brs) 4.94 (brs) 16 1.74 (s) 1.75 (s) 1.73 (s) 17 1.72 (s) 1.73 (s) 1.71 (s) 19 1.45 (s) 1.48 (s) 1.49 (s) 20 1.59 (s) 1.58 (brs) 1.59 (s) OH 3.88 (brs) 3.91 (brs) 3.90 (brs) Oac 2.08 (s) 2.06 (s) MeSen MeSen ang 2¢ 5.66 (tq, 1.2) 5.65 (tq, 1.2) 3¢ 6.06 (qq, 2.0, 9.6) 4¢ 2.17 (dq, 1.2, 7.4) 2.18 (dq, 1.2, 7.4) 1.94 (dq, 2.0, 10.0) 5¢ 1.08 (t, 7.4) 1.07 (t, 7.4) 1.79 (dq, 2.0, 2.0) 6¢ 2.18 (d, 1.2) 2.16 (d, 1.2) * Assignments from 1H-1H COSY, HMBC (from proton to carbon) and HMQC.