G Model PHYTOL 965 1–4 Phytochemistry Letters xxx (2015) xxx–xxx Contents lists available at ScienceDirect Phytochemistry Letters journal homepage: www.elsevier.com/locate/phytol Q1 Q2 Three new cassane-type furanoditerpenes from the seed of vietnamese Caesalpinia bonducella Phu Hoang Dang a , Mai Thanh Thi Nguyen a,b , Hai Xuan Nguyen a , Dung Thuy Thi Vu a , Son Van Truong a , Nhan Trung Nguyen a,b, * a b Faculty of Chemistry, University of Science, Vietnam National University, Hochiminh City, Viet nam Cancer Research Laboratory, Vietnam National University, Hochiminh City, Viet nam A R T I C L E I N F O A B S T R A C T Article history: Received April 2015 Received in revised form 18 May 2015 Accepted 20 May 2015 Available online xxx Three new cassane-type furanoditerpenes, bonducellpin H (1), bonducellpin I (2), and 7-acetoxycaesalpinin P (3), together with seven known compounds (4–10) have been isolated from the MeOH extract of the seed kernels of Caesalpinia bonducella from Vietnam The structures of these compounds were elucidated by using spectroscopic techniques ã2015 Published by Elsevier B.V on behalf of Phytochemical Society of Europe Keywords: Caesalpiniaceae Cassane-type furanoditerpenes Introduction Q3 Caesalpinia bonducella Flem (Caesalpiniaceae) is a famous medicinal plant widely distributed in tropical and subtropical regions of Southeast Asia In Vietnam, its seed kernels are used as anthelmintic, antipyretic, anti-inflammatory, and antimalarial agent, while decoction of root has been used as a tonic and for the treatment of rheumatism and backache (Bich, 2003) The plants belonging to the genus Caesalpinia are rich sources of cassane-type furanoditerpenes, some of which have been reported to show antimalaria (Banskota et al., 2003; Linn et al., 2005), antiviral (Jiang et al., 2001), and anticancer activities (Patil et al., 1997) Thus, we carried out detail phytochemical investigation of this plant and isolated three new cassane-type furanoditerpenes, bonducellpin H (1), bonducellpin I (2), and 7-acetoxycaesalpinin P (3), together with seven known compounds (4–10) from a MeOH extract of the seed kernels of this plant from Vietnam In this paper, we report the structure elucidation of these new cassane-type furanoditerpenes 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Results and discussion Air-dried seed kernels of C bonducella were extracted with reluxing MeOH, and the MeOH extract was fractionated with * Corresponding author at: Faculty of Chemistry, University of Science, Vietnam National University – Hochiminh City, Viet nam Tel.: +84 907 426 332; fax: +84 838 353 659 E-mail address: ntnhan@hcmus.edu.vn (P.H Dang) petroleum ether, CHCl3, and EtOAc to yield petroleum ether, CHCl3, and EtOAc soluble fractions, respectively The CHCl3 soluble fraction was subjected to a series of chromatographic separation and preparative TLC to afford three new cassane-type furanoditerpenes (Fig 1), bonducellpin H (1), bonducellpin I (2), and 7acetoxycaesalpinin P (3), together with seven known compounds (4–10) were identified as caesalpin H (4) (Peter et al., 1998), caesalpinin K (5) (Awale et al., 2006), caesalpinin MP (6) (Kalauni et al., 2005), caesalpinin E (7) (Kalauni et al., 2004), caesalpinin J (8) (Awale et al., 2006), 2-acetoxycaesaldekarin E (9) (Kalauni et al., 2005), norcaesalpinin MC (10) (Kalauni et al., 2004) Bonducellpin H (1) was isolated as a colorless amorphous solid and its molecular formula was determined to be C28H38O10 by HRESI-MS m/z 535.2553 [M + H]+ IR absorptions at 3650 and 1730 cmÀ1 indicated the presence of hydroxyl and carbonyl groups, respectively The 1H NMR spectrum of (Table 1) displayed signals corresponding to four methyls (H = 1.12, 1.23, 1.25, 1.36), four oxymethines (H = 5.24, 5.21, 5.46, 5.52), together with two protons of a 1,2-disubstituted furan ring (H = 6.17 and 7.22, J = 1.5 Hz), and four acetyl methyl groups (H = 2.10, 1.96, 2.02, 2.08) On the other hand, the 13C NMR spectrum of (Table 1) showed four olefinic carbons (C = 147.8, 122.0, 109.4, 141.2), an oxygenated quaternary carbon (C = 79.3), four oxygenated methine carbons (C = 75.0, 66.9, 74.8, 74.2), and eight methyl carbons together with four ester carbonyl carbons (C = 169.0, 170.3, 170.2) These 1H and 13C NMR data closely resembled those of caesalpinin K (Awale et al., 2006), except for the appearance of signals due to three more acetoxyl groups and downfield shifted signal of proton H-7 (H = 5.52) and carbon C-7 (C = 74.2) due to additional acetoxyl group attached to http://dx.doi.org/10.1016/j.phytol.2015.05.018 1874-3900/ ã 2015 Published by Elsevier B.V on behalf of Phytochemical Society of Europe Please cite this article in press as: Dang, P.H., et al., Three new cassane-type furanoditerpenes from the seed of vietnamese Caesalpinia bonducella Phytochem Lett (2015), http://dx.doi.org/10.1016/j.phytol.2015.05.018 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 G Model PHYTOL 965 1–4 P.H Dang et al / Phytochemistry Letters xxx (2015) xxx–xxx Fig Chemical structures of three new cassane-type furanoditerpenes 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 C-7 The location of the acetoxyl substituents were determined to be at C-1, C-2, C-6, and C-7, based on the HMBC correlations observed between the oxymethine protons (H-1, H-2, H-6 and H-7) and the acetyl carbonyl carbons respectively (Fig 2) The relative stereochemistry of was determined on the basis of coupling constants and the results of ROESY spectrum (Fig 3) The correlations from H3-20 to H-1, H-2, H-6, and Hax-11; from H2 to Heq-3, and H3-19 indicated that b-orientation of H-1, H-2, H319, H3-20, and H-6; and rings A and B have a chair conformation with a trans-fused junctions Moreover, the small coupling constant 3J1,2 = 3J2,3eq = 3.0 Hz indicated the acetoxyl substituents at C-1 and C-2 to be in the a-axial and a-equatorial orientation, respectively Similarly, the large coupling constant 3J6,7 = 3J7,8 = 9.0 Hz indicated the acetoxyl substituent at C-6 and C-7 to be in the a-equatorial and b-equatorial orientation, respectively The ROESY correlations from H-7 to H-9 and H3-17 also suggested the 17-Me group to be in the a-axial orientation Thus, the relative structure of bonducellpin H was assigned as (Fig 3) Bonducellpin I (2) was isolated as a colorless amorphous solid and its molecular formula was determined to be C25H30O9 by HRESI-MS m/z 475.1989 [M + H]+ IR absorptions at 1730 and 1710 cmÀ1 indicated the presence of carbonyl groups The 1H NMR spectrum of (Table 1) displayed signals corresponding to three methyls (H = 1.46, 1.11, 1.53), two oxymethines (H = 5.66 and 5.27), together with two protons of a 1,2-disubstituted furan ring (H = 6.11 and 7.22, J = 2.0 Hz), two acetyl methyls (H = 1.96 and 2.01), and a methoxyl groups (H = 3.71) Moreover, the 13C NMR spectrum of (Table 1) showed 25 carbon signals including four olefinic carbons (C = 150.4, 112.6, 108.2, 141.6), two oxygenated quaternary carbons (C = 65.8, 71.3), two oxygenated methine carbons (C = 68.3, 75.1), and five methyl carbons, together with a ketone carbonyl carbon (C = 208.2), three ester carbonyl carbons (C = 174.0, 170.0, Table The NMR data of compounds 1–3 in CDCl3 ( in ppm, multiplicities, J in Hz).a Position 1 H 13 C 5.24 (1H, d, 3.0) 5.21 (1H, m) 75.0 66.9 1.36 (1H, dd, 16.0, 3.0) 2.02 (1H, m) 37.4 5.46 (1H, dd, 9.0, 1.5) 10 11 5.52 (1H, t, 9.0) 2.10 (1H, m) 2.70 (1H, m) 12 13 14 15 16 17 18 19 20 1-OCOCH3 1-OCOCH3 2-OCOCH3 2-OCOCH3 6-OCOCH3 6-OCOCH3 7-OCOCH3 7-OCOCH3 5-OH 17-OCH3 a The H and 40.6 79.3 74.8 2.41 (1H, m) 74.2 39.8 31.6 46.2 22.6 2.70 (1H, m) 6.17 (1H, d, 1.5) 7.22 (1H, d, 1.5) 1.12 (1H, d, 7.0) 147.8 122.0 27.8 109.4 141.2 16.9 1.23 (3H, s) 1.25 (3H, s) 1.36 (3H, s) 2.10 (3H, s) 1.96 (3H, s) 2.02 (3H, s) 2.08 (3H, s) 30.7 25.8 17.1 20.9 169.0 20.8 170.2 21.0 170.3 21.5 170.3 H 2.04 (1H, dd, 13.0, 5.0) 2.75 (1H, dd, 13.0, 8.0) 2.34 (1H, d, 8.0) 5.66 (1H, d, 10.5) 5.27 (1H, d, 10.5) 2.68 (1H, t, 10.5) 2.43 (1H, m) 2.43 (1H, m) 2.96 (1H, d, 12.0) 3.50 (1H, d, 10.5) 6.11 (1H, d, 2.0) 7.22 (1H, d, 2.0) 1.46 (3H, s) 1.11 (3H, d, 7.0) 1.53 (3H, s) 13 C H 2.01 (3H, s) C 208.2 41.1 4.90 (1H, brs) 5.60 (1H, m) 75.3 75.6 35.8 1.12 (1H, m) 1.80 (1H, m) 32.4 65.8 71.3 68.3 75.1 39.6 36.7 50.8 23.8 150.4 112.6 45.1 108.2 141.6 174.0 18.0 17.0 18.0 1.80 (1H, m) 1.91 (1H, m) 5.60 (1H, m) 2.74 (1H, m) 2.74 (1H, m) 2.42 (1H, dd, 16.5, 4.5) 2.60 (1H, dd, 16.5, 10.5) 6.42 (1H, d, 2.0) 7.24 (1H, d, 2.0) 4.95 (1H, s) 5.09 (1H, s) 1.17 (3H, s) 1.16 (3H, s) 1.31 (3H, s) 2.11 (3H, s) 1.97 (3H, s) 1.96 (3H, s) 13 20.5 170.0 21.1 169.6 2.08 (3H, s) 38.6 79.3 22.1 75.2 41.7 38.1 44.6 23.3 150.6 119.8 138.6 106.5 142.0 105.6 30.7 25.0 17.1 21.4 169.1 21.3 170.8 21.7 170.8 2.95 (1H, d, 1.5) 3.71 (3H, s) 52.1 13 C NMR spectra were measured at 500 and 125 MHz, respectively Please cite this article in press as: Dang, P.H., et al., Three new cassane-type furanoditerpenes from the seed of vietnamese Caesalpinia bonducella Phytochem Lett (2015), http://dx.doi.org/10.1016/j.phytol.2015.05.018 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 G Model PHYTOL 965 1–4 P.H Dang et al / Phytochemistry Letters xxx (2015) xxx–xxx Fig Key HMBC and 1H-1H COSY correlations of three new compounds 1–3 Fig ROESY correlations of compounds and 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 169.6), and a methoxyl carbon (C = 52.1) The partial structure C(2) H2–C(3)H–C(19)H3 was deduced by HMBC correlations of the secondary methyl proton at 1.11 (H3-19) with C-2, C-3, and C4 together with 1H–1H COSY correlations of H2-2, H-3 and H319 indicated that should be a rare rearranged cassane-type furanoditerpene having one of the two methyl groups at C4 migrated to C-3 The molecular formula and the 13C NMR chemical shifts of C-4 (C = 65.8) and C-5 (C = 71.3) indicated that might contain an epoxide ring between C-4 and C-5 The 1H and 13C NMR data of were similar to those of caesalpinin (Peter et al., 1997), except for the presence of the signals due to a carbomethoxyl group assigned to C-17 and lack of the signals due to a 17-Me group and an oxygenated quaternary carbon in caesalpinin The HMBC correlations of H3-20 and H2-2 with a ketone carbonyl carbon (C = 208.2) indicated the location of the ketone carbonyl carbon to be C-1 The HMBC correlations of the methine proton H14 and methoxyl proton with an ester carbonyl carbon indicated the carbomethoxyl group should be at C-14 The location of the acetoxyl groups were determined to be C-6 and C-7, based on the analysis of the COSY, HSQC, and HMBC spectra (Fig 2) The relative stereochemistry of was determined on the basis of coupling constant and ROESY correlations (Fig 3) The ROESY correlations between Hb -2 and H3-19 and H3-20 and the coupling constant J2a,3 = 5.0 Hz and 3J2b,3 = 8.0 Hz suggesting H3-20 and H3-19 were all on the same side and to be b-oriented Since the C-5 hydroxyl substituent is biogenetically a-oriented in cassane-type diterpenes of the Caesalpinia species, the epoxide ring between C-4 and C-5 should be a-oriented (Ming et al., 2011) This was supported by the ROESY correlations of H3-18 with Hb-2, H3-19, and H3-20 Furthermore, the ROESY correlations between H3-20 with H6 suggested the a-equatorial orientation of the C-6 acetoxyl substituent, while the large coupling constant 3J6,7 = 3J7,8 = 10.5 Hz, together with the ROESY correlation between H-7 and H-9, suggested the acetoxyl substituent at C-7 to be b-equatorial oriented Similarly, the configuration of carbomethoxyl group at C14 to be b-orientation from the ROESY correlation between H- 14 and H-7 and large coupling constant 3J8,14 = 10.5 Hz Thus, the structure of bonducellpin I was determined as (Fig 3) 7-Acetoxycaesalpinin P (3) was isolated as a colorless amorphous solid and their IR spectra indicated the presence of hydroxyl and ester carbonyl groups, respectively Its molecular formula was determined to be the same C26H34O8 by HR-ESI-MS m/z 417.2285 [M + H]+ The 1H and 13C NMR spectra of were also similar to those of caesalpinin P, except for the presence of the signals due to an additional acetoxyl group Analysis of COSY, HSQC, and HMBC showed the downfield shifted signal of proton H-7 (H = 5.60), compared to that of caesalpinin P (H-7; 1.70), suggesting the location of an acetoxyl substituent to be at C-7 This was further confirmed by HMBC correlations of the proton at H 5.60 (H-7) with the ester carbonyl carbon at C 170.8 (7-OCO) (Fig 2) The relative structure of was suggested by comparision with NMR data of caesalpinin P (Awale et al., 2006) Because of the lack of amount of 3, the ROESY experiment was not recorded Furthermore, the acetoxyl substituent at C-7 is biogenetically b-oriented in cassane-type diterpenes of the Caesalpinia species (Ming et al., 2011) So, the structrure of 7-acetoxycaesalpinin P was concluded as (Fig 2) In this research, we reported the structures of three new diterpenes, bonducellpin H (1), bonducellpin I (2), and 7acetoxycaesalpinin P (3) Among the isolated compounds, and are cassane-type furanoditerpenes, and represents a rearranged cassane-type furanoditerpene in which one of the C4 methyl groups has migrated, which are the characteristic structural features of diterpenes isolated from the plant of Caesalpinia genus 125 Experimental 153 3.1 General experimental procedures 154 IR spectra were measured with a Shimadzu IR-408 spectrophotometer in CHCl3 solutions NMR spectra were taken on a Bruker Avance III 500 MHz spectrometer with tetramethylsilane (TMS) as 155 Please cite this article in press as: Dang, P.H., et al., Three new cassane-type furanoditerpenes from the seed of vietnamese Caesalpinia bonducella Phytochem Lett (2015), http://dx.doi.org/10.1016/j.phytol.2015.05.018 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 156 157 G Model PHYTOL 965 1–4 158 159 160 161 162 163 164 165 P.H Dang et al / Phytochemistry Letters xxx (2015) xxx–xxx an internal standard, and chemical shifts are expressed in values HR-ESI-MS was performed on the Agilent 6310 Ion Trap mass spectrometer The HPLC experiments were carried out on the HPLC Agilent 1100 series with UV detector Analytical and preparative TLC was carried out on precoated Merck Kieselgel 60F254 or RP18F254 plates (0.25 or 0.5 mm thickness) 3.2 Chemicals 167 The purity of isolated compounds from C bonduccella ranged 90.3–96.5% as determined by HPLC with UV detection Other chemicals were of the highest grade available 168 3.3 Plant material 169 175 The seed kernels of C bonducella Flem was collected at Khanh Hoa province, Vietnam, in October 2009 and was identified by Ms Hoang Viet, Faculty of Biology, University of Science, National University-Ho Chi Minh City A voucher sample has been deposited with the number AN-2813 at the Deparment of Analytical Chemistry of the University of Science, National University-Ho Chi Minh City, Vietnam 176 3.4 Extraction and isolation 177 Air-dried seed kernels of C bonducella (2.1 kg) were extracted with MeOH (15 L, reflux, h  3) to yield a MeOH extract (400 g) The MeOH extract was suspended in H2O and successively partitioned with petroleum ether, CHCl3, and EtOAc to yield petroleum ether (100 g), CHCl3 (40 g), EtOAc (40 g) soluble fractions and remaining aqueous fraction (220 g), respectively The CHCl3 fraction (40 g) was subjected to silica gel column (8 cm  80 cm) chromatography eluted with increasing polarity of EtOAc/petroleum ether (0–100%) and then MeOH/CHCl3 (0–30%) to give eight fractions: Fr.1–Fr.8 Fr.2 (1.2 g) was subjected to silica gel with EtOAc/petroleum ether (0–30%) to yield four sub-fractions Fr.2.1–4 Fr.3.3 and Fr.3.4 were chromatographed on silica gel column with EtOAc/ petroleum ether (20%) to give (11 mg), (5 mg), 10 (7 mg) Fr.3 (3.1 g) was chromatographed on silica gel column (3 cm  70 cm) with EtOAc/petroleum ether (0–30%) to yield five sub-fractions Fr.3.1–5 Fr.3.2 and Fr.3.3 were recrystallized with MeOH/CHCl3 led to (35 mg) and (12 mg) Fr.3.4 was subjected to silica gel with EtOAc/petroleum ether (20%) and followed by normal-phase preparative TLC with EtOAc/petroleum ether (15%) to give (18 mg) Fr.4 (1.8 g) was subjected to silica gel with MeOH/CHCl3 (20%) to obtain (23,3 mg) Fr.5 (2.8 g) was chromatographed on silica gel column with MeOH/CHCl3 (0–30%) to yield four subfractions Fr.5.1–4 Fr.5.2 and Fr.5.3 were applied to normal-phase preparative TLC with EtOAc/petroleum ether (35%) to gain (10 mg) and (8 mg) Fr.6 (1.3 g) was chromatographed on ODS with H2O/MeOH (60%) and then purified by reversed-phase preparative TLC with H2O/MeOH/CH3CN (4:3:3) to afford (12 mg) 166 170 171 172 173 174 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 3.4.1 Bonducellpin H (1) Colorless amorphous solid; mp 252.4 C; IR (CHCl3) cmÀ1: 3650, 1730; NMR data (CDCl3) see Table 1; HR-ESI-MS: m/z 535.2553 [M + H]+, calcd for C28H39O10 535.2543 206 3.4.2 Bonducellpin I (2) Colorless amorphous solid; mp 180.2 C; IR (CHCl3) cmÀ1: 1730, 1710; NMR data (CDCl3) see Table 1; HR-ESI-MS: m/z 475.1989 [M + ]+, calcd for C25H31O9 475.1968 210 3.4.3 7-Acetoxycaesalpinin P (3) Colorless amorphous solid; IR (CHCl3) cmÀ1: 3575, 1730; NMR data (CDCl3) see Table 1; HR-ESI-MS: m/z 417.2285 [M + ]+, calcd for C26H35O8 417.2277 214 Acknowledgements 218 This work was supported by Department of Science and Technology, Hochiminh City 219 Appendix A Supplementary data 221 Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j phytol.2015.05.018 222 References 225 Awale, S., Linn, T.Z., Tezuka, Y., Kalauni, S.K., Banskota, A.H., Attamimi, F., Ueda, J.-Y., Kadota, S., 2006 Constituents of 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Tanaka, K., Kadota, S., 2005 Cassane- and norcassanetype diterpenes from Caesalpinia crista of Indonesia and their antimalarial activity against the growth of Plasmodium falciparum J Nat Prod 68, 706–710 Ming, W., Yu, F.W., Man, L.Z., Chang, H.H., Mei, D., Qing, W.S., Hiromasa, K., 2011 Chemical constituents of plants from the genus Caesalpinia Chem Biodivers 8, 1370–1399 Patil, A.D., Freyer, A.J., Lee Webb, R., Zuber, G., Reichwein, R., Bean, M.F., Faucette, L., Johnson, R.K., 1997 Pulcherrimins A—D, novel diterpene dibenzoates from Caesalpinia pulcherrima with selective activity against DNA repair-deficient yeast mutants Tetrahedron 53, 1583–1592 Peter, S.R., Tinto, W.F., McLean, S., Reynolds, W.F., Tay, L.L., 1997 Caesalpinin, a rearranged cassane furanoditerpene of Caesalpinia bonducella Tetrahedron Lett 38, 5767–5770 Peter, S.R., Tinto, W.F., McLean, S., Reynolds, W.F., Tay, L.L., Yu, M., Chan, W.R., 1998 Complete 1H and 13C NMR assignments of four caesalpin furanoditerpenes of Caesalpinia bonducella Magn Reson Chem 36, 124–127 226 227 228 229 Please cite this article in press as: Dang, P.H., et al., Three new cassane-type furanoditerpenes from the seed of vietnamese Caesalpinia bonducella Phytochem Lett (2015), http://dx.doi.org/10.1016/j.phytol.2015.05.018 207 208 209 211 212 213 215 216 217 220 223 224 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 ... were measured at 500 and 125 MHz, respectively Please cite this article in press as: Dang, P.H., et al., Three new cassane-type furanoditerpenes from the seed of vietnamese Caesalpinia bonducella. .. basis of coupling constants and the results of ROESY spectrum (Fig 3) The correlations from H3-20 to H-1, H-2, H-6, and Hax-11; from H2 to Heq-3, and H3-19 indicated that b-orientation of H-1,... location of the acetoxyl groups were determined to be C-6 and C-7, based on the analysis of the COSY, HSQC, and HMBC spectra (Fig 2) The relative stereochemistry of was determined on the basis of