Phytochemistry xxx (2015) xxx–xxx

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Cytotoxic indole alkaloids from Tabernaemontana officinalis Bing-Jie Zhang a,b, Xi-Feng Teng c, Mei-Fen Bao a, Xiu-Hong Zhong a,b, Ling Ni a,b, Xiang-Hai Cai a,⇑ a

State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, People’s Republic of China University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China c School of Traditional Chinese Medicine, Guangdong Pharmaceutical University, Guangzhou 510006, People’s Republic of China b

a r t i c l e

i n f o

Article history: Received 23 July 2014 Received in revised form 12 November 2014 Available online xxxx Keywords: Tabernaemontana officinalis Apocynaceae Monoterpenoid indole alkaloid Bisindole alkaloid Cytotoxicity

a b s t r a c t Continued interest in cytotoxic alkaloids resulted in the isolation of 37 alkaloids, including 28 known monoterpenoid indole alkaloids from the aerial parts of Tabernaemontana officinalis. Of the remaining 9 alkaloids, six were bisindole alkaloids named taberdivarines A–F (1–6) and three were monomers named taberdivarines G–I (7–9). Alkaloids 1 and 2 are voaphylline–vobasinyl type bisindole alkaloids, a structural type previously unknown, while 3–6 exhibited cytotoxicity against three human cancer cell lines HeLa, MCF-7, and SW480 with IC50 values ranging from 1.42 to 11.35 lM. Ó 2014 Elsevier Ltd. All rights reserved.

1. Introduction Monoterpenoid indole alkaloids (MIAs) are of great significance in natural medicine and are well known for their distinctive structural features and significant diverse bioactivities (Saxton, 1995). Bisindole alkaloids, such as the vincristine and vinblastine derivatives, have attracted substantial attention due to their antitumor activities (Tanaka et al., 2009; Jordan and Kamath, 2007). A series of cytotoxic MIAs and their dimeric analogues were previously reported (Bao et al., 2013). Various bisindole alkaloids which exhibited diverse and fascinating molecular architecture have been isolated, such as akuammidine–ibogan, euburnane–ibogan, aspidospermatan–aspidospermatan and euburnane–aspidospermatan, vobasine–strychnan type alkaloids. More interestingly, some bisindole alkaloids rather than those with monomeric units showed cytotoxicity (Condello et al., 2014; Ma et al., 2014), which suggest that dimer formation might be key for bioactivity. Therefore, novel active dimers consisting of known and/or new monomers in various combinations deserve attention. Plants of the genus Tabernaemontana are rich in MIAs, particularly dimeric ones (VanBeek et al., 1984; Kam et al., 2003a). As part of a continuing search for new cytotoxic alkaloids, six new bisindole alkaloids and three new monomeric indole alkaloids, as well as 28 known alkaloids, were isolated from the leaves and twigs of Tabernaemontana officinalis. The known alkaloids were identified as voaphylline (10) (Kunesch et al., 1967a), 2a,7a-dihydroxydihydrovoaphylline (11) ⇑ Corresponding author. Tel.: +86 871 65223188; fax: +86 871 65150227. E-mail address: [email protected] (X.-H. Cai).

(Cai et al., 2012), voaphylline hydroxyindolenine (12) (Kunesch et al., 1967b), apparicine (13) (Joule et al., 1965), 3-(2-oxopropyl)coronaridinehydroxyindolenine (14) (Huang et al., 2006), vobasine (15) (Ahond et al., 1976), tabernaemontanine (16) (Ahond et al., 1976), dregamine (17) (Ahond et al., 1976), coronaridine (18) (Sharma and Cordell, 1988), heyneanine (19) (Gunasekera et al., 1980), isovocangine (20) (Ladhar et al., 1981), isovoaristine (21) (Wenkert et al., 1979), voacristine (22) (Wenkert et al., 1979), 3-oxo-coronaridine (23) (Sharma and Cordell, 1988), coronaridinehydroxyindolenine (24) (Sharma and Cordell, 1988), divaricatin F (25) (Bao et al., 2013), ibogamine (26) (Liang et al., 2007), 20-epi-ervatarnine (27) (Knox and Slobbe, 1975), 19-dehydroervatamine (28) (Knox and Slobbe, 1975), ervatarnine (29) (Knox and Slobbe, 1975), 3-(2-oxopropyl)coronaridine (30) (Ahond et al., 1976), 19-acetonylvoacangine (31) (Okuyama et al., 1992), ervataminic acid (32) (Knox and Slobbe, 1975), conofoline (33) (Kam et al., 2003b), 19,20-dihydroervahanine A (34) (Henriques et al., 1996), tabernaelegantine D (35) (Bombardelli et al., 1976), ervadivaricatine A (36) (Huang et al., 1997), and ervadivaricatine B (37) (Huang et al., 1997), respectively. The cytotoxicity of these alkaloids against five human cancer cell lines was evaluated in this study. 2. Results and discussion The alkaloid fraction of T. officinalis was separated as described in Section 3 to yield a total of 37 compounds, including nine new alkaloids 1–9 (Fig. 1). All compounds were most likely alkaloids as they exhibited a positive reaction with Dragendorff’s reagent.

http://dx.doi.org/10.1016/j.phytochem.2014.12.025 0031-9422/Ó 2014 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Zhang, B.-J., et al. Cytotoxic indole alkaloids from Tabernaemontana officinalis. Phytochemistry (2015), http://dx.doi.org/ 10.1016/j.phytochem.2014.12.025

2

B.-J. Zhang et al. / Phytochemistry xxx (2015) xxx–xxx 22

9 10 11

12

9'

10' 11'

12'

8

6

7 1

N H

13

8'

N H

13'

H 4N

2

6'

H 5'

4'

2'

11

N

O

19'

17'

O

N H

18'

8

10

12

13

H

14'

20' 15'

9

H N

N H

19

3'

N

21' 16'

20

22

H COOCH3 H

21

3 15

14

7' 1'

5

H COOCH3 16 H

7 1

N H

9 10

H N

N H

11

R N H H3COOC

H N

H

O

3'

10 11

H

H

5 R=H 6 R=OCH3

21

3 15

14

H 6'

7'

20

5' 4'

11'

N 2' 16' 12' 14' H H3COOC 17' H

18

H N

1'

13'

19

H

10'

21'

H R

3' 20' 19'

H

18'

15'

22'

3 R=H 4 R=acetyl

6 7 3

5

9

4

H N

21

2 16

8

10 19

11

13 N 18 14 20 H H H3COOC 17 22 H 15 7 23 6 9 5 CH2OH 8 7 3 H 1 H N 21 19 20 13 N 2 16 12 18 14 H H H3COOC 15 22 15 H 8 12

H

11'

8

H 4N

2

8'

22

H COOCH3 H

5

H COOCH3 16 H

9'

2

1

6

12

13

O

1

N

22

5

H

2

16

-

6

7

14

N+

3

4

15

O H 18

21

20 19

9

Fig. 1. Alkaloids (1–9) isolated from T. officinalis.

The UV absorption bands at 289, 227, and 208 nm and the IR vibrations at 3397 and 1721 cm1 of 1 were consistent with the presence of an indole moiety (Albinsson and Norden, 1992). The positive HRESIMS ([M+H]+ at m/z 635.3969) and 13C NMR spectroscopic data established its molecular formula as C40H50N4O3. Its 1H NMR data (Table 1) indicated the presence of a non-substituted indole ring A [dH 7.46 (d, J = 7.1 Hz), 6.91 (t, J = 7.1 Hz), 6.93 (t, J = 7.1 Hz), and 7.03 (d, J = 7.1 Hz)], a mono-substituted ring A0 [dH 7.19 (d, J = 8.1 Hz), 6.73 (d, J = 8.1 Hz), and 6.88 (s)], two indolic NH protons [dH 10.48 (s) and 10.17(s)], a nitrogen menthyl (dH 2.44, s), and a methyl ester group (dH 2.34, s), respectively (Fig. 2). These data indicated that 1 was an MIA dimer. In addition, further analysis of the DEPT and 13C NMR spectroscopic data (Table 2) of 1 established the presence of ten quaternary carbons, a methyl ester group, fourteen methines, eleven methylenes, four methyls indicating the presence of vobasine and voaphylline units. The only upfield quaternary carbon, at dC 33.2, is a characteristic resonance of C-200 in the voaphylline unit (Kunesch et al., 1967a), and the presence of seven methines dC from 60 to 30 also indicated that the other unit was a vobasine (sarpapan)-type (Sroll and Hofmann, 1953). The vobasine and voaphylline units were further confirmed by analysis of its HMQC, HMBC, and ROESY spectra and assignment of the 1H and 13C NMR spectroscopic data. The connectivity of both units was established during NMR assignment and

H3COOC

H H

A

H

N H H

H

7

A' N N H 1

H NH

N H H3COOC

HH

HN

was further supported by the HMBC spectroscopic data (S3 and S4, Supporting information), where correlations from dH 4.41 (H3) to dC 118.1 (C-100 ) and dC 109.0 (C-120 ) and from dH 6.88 (s, H120 ) to C-100 and dC 126.4 (C-80 ) verified the C-3/110 connectivity. The relative configuration of 1 was determined through analysis of the 1H and 13C NMR spectroscopic data and the ROSEY spectra. H-3 was trans-diaxial relative to 14a-H based on the large coupling constant (J = 13.0 Hz), which indicated that H-3 was in the b-orientation (Kam and Sim, 2003). H-20 was determined to be in a-orientation by examination of the resonances at C-14 (dC 42.1) and C-16 (dC 43.2), which were closer to those of tabernaemontanine than to dregamine based on comparison of the C-14/16 chemical shifts of the two isomers (Ahond et al., 1976). The ROSEY correlations from H-16 to H-5 and H-19 established the stereochemistry of 1 to be that as shown in Fig. 2. Furthermore, the shielded proton resonance (dH 2.34) of the methyl ester group suggested that it was in a b-orientation (Nugroho et al., 2009). In addition, in the voaphylline unit, correlations of H-140 /H-150 and H-150 /H-190 placed both H-150 and H-140 in an a-orientation. The above data established the structure of 1 to be that shown or its enantiomer, and 1 was named taberdivarine A. Alkaloid 2 had the same molecular formula as 1, C40H50N4O3, based on 13C NMR spectroscopic data the an ion peak at m/z 635.3972 [M+H]+, as established by HRESIMS. Similar to 1, the

O H H

N H H3COOC

OH

H N H

H H

H C HMBC

H H ROESY

8 Fig. 2. Key HMBC and ROESY correlations of 1, 7 and 8.

Please cite this article in press as: Zhang, B.-J., et al. Cytotoxic indole alkaloids from Tabernaemontana officinalis. Phytochemistry (2015), http://dx.doi.org/ 10.1016/j.phytochem.2014.12.025

3

B.-J. Zhang et al. / Phytochemistry xxx (2015) xxx–xxx Table 1 H NMR spectroscopic data for 1–6 (d in ppm and J in Hz).

1

Position

dH(1)a

dH(2)b

dH(3)c

dH(4)c

dH(5)a

dH(6)b

1 3 5 6

10.17, s 4.41, dd (13.0, 3.0) 3.78, m 3.35, m 3.03, m 7.46, d (7.1) 6.91, t (7.1) 6.93, t (7.1) 7.03, d (7.1) 2.68, m 1.89, m 2.49, m 2.70, m 0.86, t (7.4) 1.58, m 1.40, m 1.31, m 3.01, m 2.29, m 2.34, s 2.44, s 10.48, s 3.16, d (16.5) 2.54, d (16.5) 2.51, m 2.12, m 2.71, m 2.62, m 7.19, d (8.1) 6.73, d (8.1)

9.27, 4.54, 3.92, 3.47, 3.18, 7.50, 6.92, 6.94, 7.05, 2.88, 1.94, 2.62, 2.82, 0.92, 1.69, 1.51, 1.41, 3.20, 2.42, 2.41, 2.53, 9.78, 3.24, 2.62, 2.59, 2.13, 2.81, 2.75, 7.24,

s dd (13.0, 2.6) m m m d (8.4) t (8.4) t (8.4) d (8.4) m m m m t (7.3) m m m m m s s s d (12.8) d (12.8) m m m m s

10.08, s 4.41, d (11.1) 3.76, m 3.38, m 3.05, m 7.45, d (7.2) 6.89, t (7.2) 6.92, t (7.2) 7.01, d (7.2) 2.76, m 1.84, m 2.49, m 2.72, m 0.86, t (7.3) 1.60, m 1.41, m 1.31, m 3.03, m 2.33, m 2.33, br. s 2.44, s 10.25, s 2.88, m 2.70, m 3.29, m 2.97, m 3.03, m 2.83, m 7.19, s

9.30, s 4.57, dd (12.6, 3.0) 3.93, m 3.48, m 3.18, m 7.51, d (7.2) 6.94, t (7.2, 4.8) 6.96, t (7.2, 4.8) 7.08, d (7.2) 2.87, m 1.95, m 2.62, m 2.83, m 0.92, t (7.2) 1.71, m 1.51, m 1.40, m 3.15, m 2.41,m 2.42, br. s 2.54, s 9.41, s 3.34, m

9.30, s 4.56, dd (12.9, 2.7) 3.94, m 3.46, m 3.17, m 7.53, d (8.6) 6.96, t (8.6) 6.97, t (8.6) 7.09, d (8.6) 2.81, m 1.96, m 2.61, m 2.80, m 0.92, t (7.4) 1.73, m 1.51, m 1.40, m 3.12, m 2.41, m 2.42, s 2.52, s 9.39, s 3.31,m

10.05, s 4.90, d (10.8) 3.78, m 3.28, m 3.03, m 7.47, d (6.9) 6.89, t (6.9) 6.90, t (6.9) 7.04, d (6.9) 2.43, m 1.88, m 2.44, m 2.69, m 0.87, t (7.4) 1.60, m 1.38, m 1.27, m 2.93, m 2.30, m 2.32, br. s 2.44, br. s 9.85, s 3.07, m

3.24, 3.19, 3.12, 2.91, 7.25,

m m m m s

3.26, 3.17, 3.13, 2.96, 7.33, 6.91,

m m m m d (8.1) d (8.1)

3.21, 3.01, 3.02, 2.84, 6.93,

m m m m s

6.88, s 3.11, d (3.8) 2.82, d (3.8)

6.77, 7.10, 3.09, 2.84,

d d d d

6.76, 7.10, 1.84, 1.68, 1.01,

d (8.3) d (8.3) m m m

6.85, 7.15, 1.68, 1.52, 1.26,

d (8.4) d (8.4) m m m

6.95, 1.67, 1.53, 1.28,

s m m m

6.54, 1.62, 1.53, 1.29,

s m m m

3.86, 2.54, 2.01, 1.74, 0.70, 1.07,

4.11, 2.68, 2.13, 1.83, 0.72, 1.11,

m m m m t (7.4) m

2.64, 1.74, 0.81, 1.83, 1.48, 1.29, 3.42,

m m t (7.2) m m m overlap

2.73, 1.88, 0.86, 1.56, 1.43, 1.29, 3.57,

m m t (7.2) m m m s

2.71, 1.89, 0.87, 1.59, 1.42, 1.29, 3.57,

m m t (7.4) m m m s

2.54, 1.67, 0.80, 1.55, 1.42, 1.14, 3.41,

m m t (7.3) m m m overlap

9 10 11 12 14 15 16 18 19 20 21 22-OCH3 NCH3 10 30 50 60 90 100 110 120 140 150 160 17

0

0

18 190 200 210

m m m m t (7.2) m

2.27, overlap 1.58, overlap

(8.2) (8.2) (3.6) (3.6)

2.39, d (11.4) 1.67, overlap

220 -OC0 H3

3.63, s

3.64, s

3.54, s

CH2COCH3

2.77, m

2.74, m

2.61, m

2.61, m 2.09, s

2.59, m 2.08, s

2.43, m 2.02, s

CH2COCH3 110 -OCH3

3.91, s

Compound 1, 3 and 6 were recorded in DMSO-d6; 2, 4 and 5 were recorded in acetone-d6. a 1 H NMR recorded at 500 MHz. b 1 H NMR recorded at 400 MHz. c 1 H NMR recorded at 600 MHz.

UV spectrum and IR spectrum of 2 displayed characteristic absorptions of indole chromophores. Comparison of the 1H and 13C NMR spectroscopic data (Tables 1 and 2) of 2 with those of 1 suggested that both alkaloids shared the same units but were connected differently. Correlation of dH 4.54 (dd, J = 13.0, 2.6 Hz, H-3) with dC 116.9 (C-90 ) and dC 120.9 (C-110 ) and of dH 7.24 (s, H-90 ) with dC 109.4 (C-70 ) and 135.6 (C-130 ) indicated a C-3/C-100 linkage. Analysis of the 2D NMR spectroscopic data confirmed that 1 and 2 had the same stereochemistry. Hence, structure 2 was determined to be that shown, and it was named taberdivarine B. The UV and IR spectra of 3 and 4 exhibited characteristic features of indoles. The molecular formula of alkaloid 3 was established as C42H52N4O4 based on the HRESIMS ([M+H]+ at m/z 677.4081) and 13 C NMR spectroscopic data. Analysis of its 1H NMR data (Table 2) indicated presence of two indolic NH protons at dH 10.25 (1H, s)

and 10.08 (1H, s), typical of an unsubstituted indole A-ring, dH 7.45 (d, J = 7.2 Hz), 7.01 (d, J = 7.2 Hz), 6.92 (t, J = 7.2 Hz) and 6.89 (t, J = 7.2 Hz). In addition, features of a mono-substituted indole were present at dH 7.19 (1H, s), 7.10 (d, J = 8.3 Hz) and 6.76 (d, J = 8.3 Hz). The 13C NMR and DEPT data of 3 (Table 2) established eleven quaternary carbons, a methyl ester group, fifteen methines, ten methylenes, two methyls, two methoxy groups and a nitrogen methyl. Alkaloid 3 was thus identified as a bisindole alkaloid consisting of vobasinyl- and iboga-type units, similar to 19, 20-dihydroervahanine A (Henriques et al., 1996). The most likely linkage of the two moieties in 3 was at C-3/C-100 , instead of the C-3/C-110 linkage in 19. This assumption was supported by HMBC correlations of dH 4.41 (d, J = 11.1 Hz, H-3) with dC 116.4 (C-90 ) and dC 120.9 (C-110 ) and of dH 7.19 (H-90 ) with dC 134.5 (C-130 ) and 108.9 (C-70 ). Correlations of H-5/H-16 and H-16/H-19 in the ROESY spectrum

Please cite this article in press as: Zhang, B.-J., et al. Cytotoxic indole alkaloids from Tabernaemontana officinalis. Phytochemistry (2015), http://dx.doi.org/ 10.1016/j.phytochem.2014.12.025

4

B.-J. Zhang et al. / Phytochemistry xxx (2015) xxx–xxx

Table 2 C NMR spectroscopic data for 1–6 (d in ppm).

13

Position

dC(1)a

dC(2)b

dC(3)c

dC(4)c

dC(5)a

dC(6)b

2 3 5 6 7 8 9 10 11 12 13 14 15 16 18 19 20 21 22

138.0 44.9 59.2 17.1 108.6 129.5 117.2 117.6 120.4 109.8 136.1 42.1 34.4 43.2 12.7 25.2 42.4 46.6 171.1 49.2

139.3 46.4 60.3 18.0 110.0 130.9 118.1 118.7 121.4 110.4 137.4 43.0 35.7 44.5 13.0 26.3 43.7 47.7 172.1 49.8

138.4 45.1 59.3 17.1 108.4 129.6 117.3 117.7 120.5 109.8 136.2 41.9 34.4 43.3 12.8 25.3 42.5 46.7 171.3 49.3

139.2 46.4 60.4 18.0 110.2 130.9 118.3 118.8 121.6 110.7 137.5 43.1 35.8 44.5 13.0 26.3 43.9 47.7 172.3 49.8

138.8 46.4 60.4 18.1 110.4 130.1 118.2 118.9 121.6 110.7 137.5 43.1 35.9 44.6 13.0 26.4 43.8 47.7 172.3 49.8

137.8 37.4 59.2 16.6 109.9 129.5 117.0 117.6 120.4 109.9 136.2 39.6 34.3 43.0 12.7 25.2 42.5 46.5 171.2 49.2

42.8 139.3 53.5 53.3 25.6 107.5 126.4 117.0 118.1 138.7 109.0 135.6 51.5 58.3 22.4 35.7 7.4 31.8 33.2 57.6

42.9 140.9 54.6 54.4 26.6 109.4 129.4 116.9 138.2 120.9 110.9 135.6 52.4 59.5 23.7 36.9 7.6 32.9 34.2 59.1

42.9 137.1 52.7 53.4 21.4 108.9 128.1 116.4 138.3 120.9 110.9 134.5 26.5 31.8 54.6 35.9 11.7 26.8 38.1 56.7 174.2 52.5

43.3 139.0 56.5 52.3 22.6 110.1 129.7 117.6 138.4 122.4 111.6 135.9 31.7 27.7 55.8 38.3 12.1 27.6 38.8 59.0 175.2 52.8

43.3 138.4 56.9 52.4 22.6 110.2 128.1 118.7 120.1 141.4 110.5 137.0 31.8 27.6 55.7 38.2 12.0 27.7 38.8 58.8 175.1 52.8

42.7 137.6 55.3 51.2 21.5 108.5 126.4 98.8 150.3 136.4 110.8 130.6 30.2 26.4 55.5 36.9 11.7 26.6 37.5 56.9 173.8 52.3

22-OCH3 NCH3 20 30 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 220 -OCH3 CH2COCH3

46.7

46.9

46.2

CH2COCH3

208.4

208.1

208.7

CH2COCH3

30.8

30.1

110 -OCH3

30.7 56.0

Compounds 1, 3 and 6 were recorded in DMSO-d6; 2, 4 and 5 were recorded in acetone-d6. a 13 C NMR recorded at 125 MHz. b 13 C NMR recorded at 100 MHz. c 13 C NMR recorded at 150 MHz.

indicated that the relative configuration of 3 was the same as that of 19, 20-dihydroervahanine A. The molecular formula of 4 was determined to be C45H56N4O5 by HRESIMS ([M+H]+ at m/z 733.4337) and 13C NMR spectroscopic data, which was 56 mass units higher than that of 3. Thus alkaloid 4 was readily identified to be a 2-oxopropyl derivative of 3 from the presence of resonances at dC 208.4 (s), 46.7 (t) and 30.8 (q) in its 13C NMR data (Table 2). The HMBC correlation of dH 2.77 and 2.61 (CH2COCH3, m) with C-30 (dC 56.5, d) indicated that the 2-oxopropyl group was located at C-30 . The ROESY correlation of H-30 with H-50 b and H-170 b suggested that H-30 was in a b-orientation. Detailed analysis of the 2D NMR spectroscopic data confirmed that the other parts of the structure were the same as alkaloid 3. Thus, structures of 3 and 4 were established, and the alkaloids were named taberdivarines C and D, respectively. The UV and IR spectra of 5 and 6 exhibited characteristics of indole chromophores. Alkaloid 5 had the same molecular formula

as 4, C45H56N4O5, as determined by HRESIMS ([M+H]+ at m/z 733.4322) and 13C NMR spectroscopic data. The proton resonances of the mono-substituted indole ring A [dH 7.33 (d = 8.1 Hz), 6.91 (d = 8.1 Hz), 6.95 (s)] of 5 differed from those of 4, indicating a difference in the linkage of the two units between 4 and 5. The presence of the C-3/C-110 linkage in 5 rather than the C-3/C-100 linkage in 4 was confirmed by the HMBC correlations of dH 4.56 (dd, J = 12.9, 2.7 Hz, H-3) with dC 120.1 (C-100 ) and dC 110.5 (C-120 ). Analysis of the ROESY spectrum of 5 indicated that the relative configuration of 5 was the same as that of alkaloid 4. The molecular formula of 6 was established as C46H58N4O6 by HRESIMS ([M+H]+ at m/z 763.4446) and 13C NMR spectroscopic data, which was 30 mass units higher than that of 5. Comparison of the NMR data for 5 and 6 suggested that they shared the same skeleton, with the exception of an additional methoxy group on the indole A-ring of 6. The HMBC correlations of dH 6.93 (s, H-90 ) with dC 136.4 (C-110 ) and 130.6 (C-130 ) and dH 6.54 (s, H-120 ) with dC 150.3 (C-100 ) and 126.4 (C-80 ) supported the presence of an additional methoxy group at C-100 . Further analysis of the 2D-NMR data indicated that the remaining portions of the two alkaloids were the same. Hence, the structures of 5 and 6 were established, and they were named taberdivarines E and F, respectively. Alkaloids 7–9 were determined to be monomeric MIAs based on their NMR and MS data. The molecular formula of 7 was established as C21H25N2O2 by HRESIMS ([M]+ at m/z 337.1917) and 13C NMR spectroscopic data. Its UV absorption bands at 285 and 223 nm indicated a mono-indole nucleus. The 13C NMR data (Table 3) indicated the presence of five quaternary carbons, a methyl ester, eight methines, five methylenes, and one methyl group. The NMR data for 7 were strikingly similar to those of coronaridine (Sharma and Cordell, 1988), with the exception of the presence of a downfield sp3 methine resonance (dC 86.6) instead of a methylene at dC 50 for coronaridine. The methine carbon resonance was correlated with dH 3.76 (H-21), 3.43 and 3.25 (H-5), 2.76 and 1.74 (H-17), and 1.55 and 1.48 (H-15) in the HMBC spectrum, thus determining that this resonance corresponded to C-3. Thus, structure of alkaloid 7 was established, and it was named taberdivarine G. Alkaloid 8 had a molecular formula of C22H28N2O3 as determined by HRESIMS and 13C NMR spectroscopic data. The 13C NMR pattern of 8 was very similar to that of coronaridine (Sharma and Cordell, 1988). The alkaloids differed in the presence of an additional hydroxymethyl (dC 62.1) in 8 compared to coronaridine. The HMBC correlations from dH 2.78 (m, H-3), corresponding to a methine (dC 63.1), to dC 53.2 (C-5), 38.5 (C17), and 27.6 (C-15) indicated that the methine was C-3. Furthermore, the HMBC correlations from dH 3.59 and 3.41 of the hydroxymethyl group to C-3 and C-14 (dC 28.8) indicated that the hydroxymethyl group was on C-3. H-3 was determined to be in the a-orientation based on the ROESY correlation of H-3/H19(18). Hence, structure 8 was established, and it was named taberdivarine H. The molecular formula of 9 was determined to be C20H22N2O2 by HRESIMS (m/z = 345.1585 [M+Na]+). The DEPT and 13C NMR spectroscopic data (Table 3) indicated that 9 possessed five quaternary carbons, an ester carbonyl, eight methines, four methylenes, and two methyls, including a nitrogen menthyl, similar to 16epi-pleiocarpamine (Hesse et al., 1964). However, the correlation of the methyl at dC 47.0 with C-3 and C-21, C-5 and the carbon resonance at dC 174 suggested that the methyl group was attached to N-4. Moreover, X-ray diffraction of 9 indicated that it was the inner-salt (Fig. 3). Thus alkaloid 9 was named 3S, 15S, 16R, 19Etaberdivarine I. All alkaloids were evaluated for their cytotoxicity against breast cancer (MCF-7), colon cancer (SW480), and HeLa cells using the

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5

B.-J. Zhang et al. / Phytochemistry xxx (2015) xxx–xxx Table 3 H NMR and

1

13

C NMR spectroscopic data for 7–9 (d in ppm and J in Hz).

Position

7a

8b

N-H 2 3 5

9.60, br. s

dH

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 22-OCH3 23

4.36, 3.43, 3.25, 2.10,

7.45, 6.97, 7.02, 7.37,

dC

d (5.3) m m m

d (7.8) t (7.8) t (7.8) d (7.8)

1.78, m 1.55, m 1.48, m 2.76, 1.94, 0.88, 1.66, 1.53, 1.38, 3.76,

m m t (7.4) m m m s

3.62, s

9a

dH

dC

dH

dC

9.56, br. s 138.3 86.6 52.3 22.4 110.2 129.2 118.6 119.4 121.9 111.5 137.1 35.7 25.4 55.1 35.9 11.9 27.3 38.4 57.2 174.8 52.6

2.78, 3.35, 3.27, 3.15, 3.03,

7.45, 6.98, 7.04, 7.31,

138.6 63.1 53.2

m m m m m

22.4 110.4 129.5 118.8 119.5 122.1 111.6 137.3 28.8

d (7.8) t (7.8) t (7.8) d (7.8)

2.00, m 1.51, m 1.31, m 2.78, 1.90, 0.87, 1.58, 1.39, 1.29, 3.63,

27.6

dd (13.2, 1.8) dd (13.2, 1.8) t (7.2) m m m s

4.82, 3.78, 3.21, 3.33,

7.62, 7.17, 7.27, 7.37,

s m m m

d (8.0) t (8.0) t (8.0) d (8.0)

2.69, d (15.2) 2.52, d (15.2) 3.84, s

20.2 111.6 128.1 120.5 122.1 124.8 112.2 141.4 20.4 33.1

55.9 38.5

4.49, s

64.6

12.1 27.4

1.80, d (6.8) 5.55, q (6.8, 12.8)

13.6 132.1

38.8 58.4

3.12, br. s 1.75, br. s

175.3 52.8 62.1

3.64, s 3.59, m 3.41, m

133.3 62.2 64.7

NCH3:

129.4 65.7 176.3

3.18, s

47.0

Compounds 7 and 8 were recorded in acetone-d6; 9 was recorded in methanol-d4. a 1 H NMR recorded at 400 MHz, 13C NMR recorded at 100 MHz. b 1 H NMR recorded at 600 MHz, 13C NMR recorded at 150 MHz.

Table 4 Alkaloid cytotoxicity data (IC50, lM). Alkaloids.

HeLa

MCF-7

SW480

3 4 5 6 Cisplatin

3.14 ± 0.22 1.62 ± 0.13 1.42 ± 0.32 1.52 ± 0.14 12.84 ± 0.88

11.35 ± 0.90 2.84 ± 0.53 5.43 ± 0.56 3.76 ± 0.22 9.63 ± 0.78

5.37 ± 0.32 2.31 ± 0.35 1.57 ± 0.62 2.45 ± 0.44 16.63 ± 1.19

3. Concluding remarks Alkaloids 1 and 2 were the first reported dimers that contained the voaphylline unit. Alkaloid 7 was the first monomer isolated with a carbon connected to both N-1 and N-4. In addition, 8 was an iboga alkaloid with an additional carbon. Other alkaloids (10– 37) were identified by comparison of their NMR and mass spectroscopic data with the literature.

4. Experimental 4.1. General experimental procedures

Fig. 3. Crystal structure of 9.

previously reported MTT method (Mosmann, 1983). Alkaloids 3–6, which were vobasinyl–iboga dimers, exhibited moderate cytotoxicity (Table 4).

Melting points were obtained on a X-4 micro melting point apparatus and is uncorrected. Optical rotations were measured with a Horiba SEPA-300 polarimeter. UV spectra were recorded on a Shimadzu 2401A spectrophotometer. IR spectra were obtained on a Bruker Tensor 27 infrared spectrophotometer with KBr pellets. 1H, 13C and 2D NMR spectra were acquired on Bruker Avance III-600, DRX-500, and AM-400 MHz spectrometers with SiMe4 as an internal standard. MS data were obtained using an Agi-

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B.-J. Zhang et al. / Phytochemistry xxx (2015) xxx–xxx

lent G6230 TOF MS. Column chromatography (CC) was performed on either silica gel (200–300 mesh, Qing-dao Haiyang Chemical Co., Ltd., Qingdao, China) or RP-18 silica gel (20–45 lm, Fuji Silysia Chemical Ltd., Japan). Fractions were monitored by TLC on silica gel plates (GF254, Qingdao Haiyang Chemical Co., Ltd., Qingdao, China), and spots were visualized with Dragendorff’s reagent spray. MPLC was performed using a Buchi pump system coupled with RP18 silica gel-packed glass columns (15  230 and 26  460 mm, respectively). HPLC was performed using Waters 1525E pumps coupled with analytical semi-preparative or preparative Sunfire C18 columns (4.6  150, 10  150, and 19  250 mm, respectively). The HPLC system employed a Waters 2996 photodiode array detector and a Waters fraction collector II. 4.2. Plant material Leaves and twigs of T. officinalis (Tsiang) P.T. Li were collected in February 2012 in Guangzhou Province, P.R. China, and identified by Dr. Xi-Feng Teng. A voucher specimen (No. Cai20120227) is deposited in the State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences. 4.3. Extraction and isolation An air-dried, powdered sample (12 kg) was extracted with MeOH (3  25 L) at room temperature for a week, and the solvent was removed in vacuo. The extract (654.2 g) was partitioned between EtOAc and 0.5% HCl solution. The aqueous acidic layer then was basified with 10% ammonia solution to pH 9–10 and partitioned with EtOAc to afford the crude alkaloid (72.3 g). The latter fraction was subjected to silica gel CC eluting with a CHCl3–Me2CO gradient (1:0–0:1, v/v) to yield eight fractions (I–VII). Fraction I (2.3 g) was further subjected to silica gel CC using a petroleum ether-acetone gradient eluent (from 25:1 to 15:1, v/v) to afford 7 (8.9 mg), 8 (87.5 mg), 17 (32.1 mg), and 10 (8.9 mg), respectively. Fraction II (5.0 g) was purified by silica gel CC with petroleum ether–acetone (25:1–10:1, v/v) as eluent to afford four subfractions (II-1-II-4). II-1 (0.9 g) was separated using C18 MPLC column with a gradient of MeOH–H2O (60:40–80:20, v/v) to afford 19 (87.5 mg) and 25 (7.8 mg). II-2 (0.3 g) was purified by C18 HPLC column with a gradient of MeOH–H2O (60:40–80:10, v/v) to obtain 18 (20.1 mg). II-3 (0.9 g) was purified by C18 MPLC column with a gradient of MeOH–H2O (50:50–70:30, v/v) to afford alkaloid 22 (5.7 mg). II-4 (0.3 g) was purified by C18 HPLC column with a gradient of MeOH–H2O (60:40–90:10, v/v) to obtain 27 (10.7 mg), 28 (33.4 mg) and 29 (56.4 mg). Alkaloid 16 (5.6 g) was crystallized from Fr. III. The mother liquid of this fraction (2.1 g) was further separated using a C18 MPLC column with a gradient of MeOH– H2O (40:60–70:30, v/v) and then separated on a preparative C18 HPLC column with a gradient of MeOH–H2O (55:45–65:35, v/v) to afford 14 (9.8 mg), 20 (8.6 mg), 21 (15.7 mg), 23 (10.3 mg) and 24 (2.4 mg). IV (2.3 g) was purified by C18 MPLC column with a gradient of MeOH–H2O (50:50–80:20, v/v) to obtain three subfractions (IV-1-IV-3). Alkaloid 15 (230 mg) was crystallized from IV3. IV-1 (0.5 g) was further subjected to silica gel CC eluting with a petroleum ether–acetone gradient (8:1–1:1, v/v) to afford 31 (67.8 mg). IV-2 (1.2 g) was separated using C18 MPLC column with a gradient of MeOH–H2O (55:45–60:40, v/v) to give the two fractions (IV-2-1 and IV-2-2). IV-2-2 was further separated on a preparative C18 HPLC column with a MeOH–H2O gradient (55:45– 65:35, v/v) to afford 26 (20.2 mg) and 30 (17.3 mg). IV-3 (0.9 g) was subjected to C18 MPLC column with a gradient of MeOH– H2O (40:60–70:30, v/v) and then separated on a preparative C18

HPLC column with a gradient of MeOH–H2O (55:45–65:35, v/v) to give 6 (17.5 mg). Fraction V (8.0 g) was subjected to C18 MPLC column with a gradient of MeOH–H2O (38:62–70:30, v/v) to yield four subfractions (V-1-V-4). V-2 (1.0 g) was further separated by silica gel CC with a petroleum ether–acetone gradient eluent (15:1–9:1, v/v) to afford 35 (157 mg) and subfraction V-2-2. V-22 (260 mg) was purified on a preparative C18 HPLC column with a gradient of MeOH–H2O (55:45–65:35, v/v) to afford 13 (24.6 mg). V-3 (0.5 g) was subjected to silica gel CC eluting with a petroleum ether–acetone gradient (15:1–9:1, v/v) to give 11 (23.5 mg). V-4 (1.3 g) was separated by C18 MPLC column with a gradient of MeOH–H2O (55:45–100:0, v/v) to give four subfractions (V-4-1-V-4-4). These four subfractions were purified using a preparative C18 HPLC column with a gradient of MeOH–H2O (85:15– 95:5, v/v) to afford 4 (32.6 mg), 5 (4.7 mg), 12 (15.3 mg), 36 (8.3 mg) and 37 (6.7 mg), respectively. VI (6.9 g) was further separated using a C18 MPLC column with a gradient of MeOH–H2O (40:60–70:30, v/v) to give three subfractions (VI-1-VI-3). VI-1 (3.1 g) was subjected to silica gel CC eluting with a CHCl3–Me2CO gradient (8:1–1:1) to obtain two fractions (VI-1-1 and VI-1-2). VI-1-1 (0.22 g) was further separated on a preparative C18 HPLC column with a gradient of MeOH–H2O (40:60–55:45, v/v) to afford 13 (34.8 mg) and 34 (374 mg). VI-2 (1.2 g) was separated by silica gel CC using a CHCl3–Me2CO gradient eluent (5:1–1:1) to obtain 3 (32.6 mg), 32 (14.5 mg) and 33 (6.4 mg). VII (8.0 g) was purified by C18 MPLC column with a gradient of MeOH–H2O (30:70–70:30, v/v) to afford subfraction VII-1. Alkaloid 9 (178 mg) was crystallized from VII-1. VIII (20.3 g) was separated by C18 MPLC column with a gradient of MeOH–H2O (15:85–65:35, v/v) to give two subfractions (VIII-I-VIII-II). VIII-I (8.2 g) was further subjected to silica gel CC eluting with a CHCl3–Me2CO gradient (5:1–0:1) to afford five subfractions (VIII-I-1-VIII-I-5). VIII-I-1 (1.7 g) was further purified by silica gel CC using a CHCl3–MeOH gradient (20:1–9:1) to obtain three subfractions (VIII-I-1-1-VIII-I-1-3). VIII-I-1-1 (0.36 g) was further separated on a preparative C18 HPLC column with a gradient of MeOH–H2O (35:65–50:50, v/v) to give 31 (67.8 mg). VIII-I-1-3 (0.33 g) was subjected to a preparative C18 HPLC column with a MeOH–H2O gradient (37:63–55:45, v/v) to yield 14 (9.8 mg) and 16 (5.6 g). VIII-I-2 (1.5 g) was purified using a silica gel column with a CHCl3–MeOH gradient (20:1–9:1) to afford two subfractions (VIII-I-2-1 and VIII-I-2-2). VIII-I-2-1 (0.21 g) was further purified on a preparative C18 HPLC column with a gradient of MeOH–H2O (40:60–55:45, v/v) to give 35 (157 mg). Alkaloid 9 (178 mg) was crystallized from VIII-I-3. VIII-I-4 (0.35 g) was further separated on a preparative C18 HPLC column with a gradient of MeOH–H2O (40:60 to 55:45, v/v) to give 6 (17.5 mg). VIII-5 (0.42 g) was further separated on a preparative C18 HPLC column with a gradient of MeOH-H2O (40:60–55:45, v/v) to give 4 (32.6 mg). VIII-II (4.7 g) was applied to a silica gel column using a CHCl3–Me2CO gradient eluent (5:1–0:1) to give three subfractions (VIII-II-1-VIII-II-3). VIII-II-1 (0.9 g) was further separated by silica gel CC using a CHCl3–MeOH eluent (10:1) to obtain VIII-II-1-1. VIII-II-1-1 (0.31 g) was purified on a preparative C18 HPLC column with a gradient of MeOH–H2O (65:35–75:25, v/v) to afford 2 (21.5 mg). VIIIII-2 (0.43 g) was further separated on a preparative C18 HPLC column with a gradient of MeOH–H2O (65:35–75:25, v/v) to give 1 (14.1 mg). 4.3.1. Taberdivarine A (1) White powder: ½a25 D 29.4 (c 0.9, MeOH); UV (MeOH) kmax (log e) 289 (3.42), 227 (3.88), 208 (3.85) nm; IR (KBr) mmax 3397, 2927, 1721, 1637, 1463, 1384 cm1; for 1H (500 MHz) and 13C NMR (125 MHz) spectroscopic data (DMSO-d6), see Tables 1 and 2; positive HRESIMS m/z 635.3969 [M+H]+ (calcd. for C40H51N4O3, 635.3961).

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B.-J. Zhang et al. / Phytochemistry xxx (2015) xxx–xxx

4.3.2. Taberdivarine B (2) 25 D

White powder: ½a 38.5 (c 1.0, MeOH); UV (MeOH) kmax (log e) 288 (3.42), 228 (3.89), 208 (3.84) nm; IR (KBr) mmax 3429, 2926, 2873, 1722, 1630, 1462, 1012 cm1; for 1H (400 MHz) and 13C NMR (100 MHz) spectroscopic data (acetone-d6), see Tables 1 and 2; positive HRESIMS m/z 635.3972 [M+H]+ (calcd. for C40H51N4O3, 635.3961). 4.3.3. Taberdivarine C (3) White powder: ½a25 D 19.4 (c 0.9, MeOH); UV (MeOH) kmax (log e) 289 (3.56), 228 (4.02) nm; IR (KBr) mmax 3327, 2930, 2870, 1712, 1630, 1461 cm1; for 1H (600 MHz) and 13C NMR (150 MHz) spectroscopic data (DMSO-d6), see Tables 1 and 2; positive HRESIMS m/ z 677.4081 [M+H]+ (calcd. for C42H53N4O4, 677.4067).

7

space group P212121, Z = 4, l(Cu Ka) = 0.787 mm1, 8754 reflections measured, 3282 independent reflections (Rint = 0.0341). The final R1 values were 0.0317 (I > 2r(I)). The final wR(F2) values were 0.0812 (I > 2r(I)). The final R1 values were 0.0317 (all data). The final wR(F2) values were 0.0812 (all data). The goodness of fit on F2 was 1.083. Flack parameter = 0.02(16). The Hooft parameter was 0.10(5) for 1341 Bijvoet pairs. The crystallographic data supporting the structure of 9 have been deposited in the Cambridge Crystallographic Centre (deposition No. is 1003805). Copies of these data can be obtained, free of charge, by application to CCDC at www. ccdc.cam.ac.uk/conts/retrieving.html (or 12 Union Road, Cambridge CB2 1EZ, UK; Fax: +44 1223 336033, email: [email protected] uk). 4.4. Cytotoxicity assay

4.3.4. Taberdivarine D (4) White powder: ½a25 D 15.1 (c 1.3, MeOH); UV (MeOH) kmax (log e) 289 (3.55), 229 (4.03) nm; IR (KBr) mmax 3427, 2928, 2871, 1722, 1630, 1461, 1227, 1009 cm1; for 1H (600 MHz) and 13C NMR (150 MHz) spectroscopic data (acetone-d6), see Tables 1 and 2; positive HRESIMS m/z 733.4337 [M+H]+ (calcd. for C45H57N4O5, 733.4329). 4.3.5. Taberdivarine E (5) White powder: ½a25 D 23.1 (c 1.0, MeOH); UV (MeOH) kmax (log e) 288 (3.51), 231 (4.02) nm; IR (KBr) mmax 3427, 2929, 2871, 1720, 1628, 1462, 1237, 742 cm1; for 1H (500 MHz) and 13C NMR (125 MHz) spectroscopic data (acetone-d6), see Tables 1 and 2; positive HRESIMS m/z 733.4322 [M+H]+ (calcd. for C45H57N4O5, 733.4329). 4.3.6. Taberdivarine F (6) White powder: ½a25 D 9.4 (c 0.9, MeOH); UV (MeOH) kmax (log e) 293 (3.17), 226 (3.62) nm, 202 (3.65) nm; IR (KBr) mmax 3418, 2931, 2872, 1724, 1630, 1464, 1222, 741 cm1; for 1H (400 MHz) and 13C NMR (100 MHz) spectroscopic data (DMSO-d6), see Tables 1 and 2; positive HRESIMS m/z 763.4446 [M+H]+ (calcd. for C46H59N4O6, 763.4435). 4.3.7. Taberdivarine G (7) White powder: ½a25 D 24.5 (c 1.0, MeOH); UV (MeOH) kmax (log e) 284 (3.17), 223 (3.62) nm; IR (KBr) mmax 3347, 2925, 2872, 1702, 1490, 1453, 1280 cm1; for 1H (400 MHz) and 13C NMR (100 MHz) spectroscopic data (acetone-d6), see Table 3; positive HRESIMS m/z 337.1917 [M]+ (calcd. for C21H25N2O2, 337.1916). 4.3.8. Taberdivarine H (8) White powder: ½a25 D 10.3 (c 1.5, MeOH); UV (MeOH) kmax (log e) 285 (2.50), 224 (3.10) nm; IR (KBr) mmax 3448, 2924, 2856, 1722, 1637, 1383, 717 cm1; for 1H (600 MHz) and 13C NMR (150 MHz) spectroscopic data (acetone-d6), see Table 3; positive HRESIMS m/z 369.2182 [M+H]+ (calcd. for C22H29N2O3, 369.2178). 4.3.9. Taberdivarine I (9) Prism crystals: m.p., 212–215 °C; ½a25 D +235.2 (c 1.3, MeOH); UV (MeOH) kmax (log e) 282 (3.13), 225 (3.77) nm, 206 (3.63) nm; IR (KBr) mmax 3443, 2934, 1693, 1449, 1386, 760 cm1; for 1H (400 MHz) and 13C NMR (100 MHz) spectroscopic data (methanol-d4), see Table 3; positive HRESIMS m/z 345.1585 [M+Na]+ (calcd. for C20H22N2NaO2, 345.1579). 4.3.10. X-ray crystallographic data for 9 C20H22N2O23(H2O), M = 376.44, orthorhombic, a = 11.0569(2) Å, b = 12.1433(2) Å, c = 13.9361(3) Å, V = 1871.16(6) Å3, T = 100(2) K,

Three human cancer cell lines, breast cancer (MCF-7), colon cancer (SW480), and HeLa cells, were used in the cytotoxicity assay. All cells were cultured in RPMI-1640 or DMEM medium (Hyclone, USA) supplemented with 10% fetal bovine serum (Hyclone, USA) in 5% CO2 at 37 °C. The cytotoxicity assay was performed using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) method in 96-well microplates. Briefly, 100 lL of adherent cells was seeded into each well of a 96-well cell culture plate and allowed to adhere for 12 h before drug addition, while suspended cells were seeded just before drug addition with an initial density of 1  105 cells/mL. Each tumor cell line was exposed to the test compound at concentrations of 0.0624, 0.32, 1.6, 8, and 40 lM in triplicate for 48 h, with cisplatin (Sigma, USA) as a positive control. After compound treatment, cell viability was detected and cell growth curves were plotted. IC50 values were calculated according to the method of Reed and Muench. Acknowledgments This project was supported in part by the National Natural Science Foundation of China (21172225, 31370377), the National New Drug Innovation Major Project of China (2013ZX09102113), the Young Academic and Technical Leader Raising Foundation of Yunnan Province (No. 2010CI049), and the XiBuZhiGuang Project of the Chinese Academy of Sciences. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.phytochem.2014. 12.025. References Ahond, A., Bui, A.M., Potier, P., Hagaman, E.W., Wenkert, E., 1976. Carbon-13 nuclear magnetic resonance analysis of vobasine-like indole alkaloids. J. Org. Chem. 41, 1878–1879. Albinsson, B., Norden, B., 1992. Excited-state properties of the indole chromophore: electronic transition moment directions from linear dichroism measurements: effect of methyl and methoxy substituents. J. Phys. Chem. 96, 6204–6212. Bao, M.F., Yan, J.M., Cheng, G.G., Li, X.Y., Liu, Y.P., Li, Y., Cai, X.H., Luo, X.D., 2013. Cytotoxic indole alkaloids from Tabernaemontana divaricate. J. Nat. Prod. 76, 1406–1412. Bombardelli, E., Bonati, A., Gabetta, B., Martinelli, E.M., Mustich, G., Danieli, B., 1976. Structures of tabernaelegantines A–D and tabernaelegantinines A and B, new indole alkaloids from Tabernaemontana eiegans. J. Chem. Soc. Perkin Trans. 1, 1432–1438. Cai, X.H., Li, Y., Liu, Y.P., Li, X.N., Bao, M.F., Luo, X.D., 2012. Alkaloids from Melodinus yunnanensis. Phytochemistry 83, 116–124. Condello, M., Cosentino, D., Corinti, S., Di Felice, G., Multari, G., Gallo, F.R., Arancia, G., Meschini, S., 2014. Voacamine modulates the sensitivity to doxorubicin of resistant osteosarcoma and melanoma cells and does not induce toxicity in normal fibroblasts. J. Nat. Prod. 77, 855–862.

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B.-J. Zhang et al. / Phytochemistry xxx (2015) xxx–xxx

Gunasekera, S.P., Cordell, G.A., Farnsworth, N.R., 1980. Anticancer indole alkaloids of Ervatamia heyneana. Phytochemistry 19, 1213–1218. Henriques, A.T., Melo, A.A., Moreno, P.R.H., Ene, L.L., Henriques, J.A.P., Schapoval, E.E.S., 1996. Ervatamia coronaria: chemical constituents and some pharmacological activities. J. Ethnopharmacol. 50, 19–25. Hesse, M., Philipsborn, W.V., Schumann, D., Spiteller, G., Spiteller-Friedmann, M., Taylor, W.I., Schmid, H., Karrer, P., 1964. Die strukturen von C-fluorocurin, Cmavacurin und pleiocarpamin. 57. Mitteilung über curare-alkaloide. Helv. Chim. Acta. 47, 878–911. Huang, L., Zhou, Y., Li, C., Wang, C., 1997. Studies on the alkaloids of Erchagouyahua (Ervatamia divaricata). Zhongcaoyao 28, 451–454. Huang, J.P., Feng, Z.M., Zheng, C.F., Zhang, P.C., Ma, Y.M., 2006. Indole alkaloids from the roots of Ervatamia hainanensis. Chin. Chem. Lett. 17, 776–782. Jordan, M.A., Kamath, K., 2007. How do microtubule-targeted drugs work? An overview. Curr. Cancer Drug Targets 7, 730–742. Joule, J.A., Monteiro, H., Durham, L.J., Gilbert, B., Djerassi, C., 1965. Alkaloid studies. Part XLVIII. The structure of apparicine, a novel Aspidosperma alkaloid. J. Chem. Soc., 4773–4780 Kam, T.S., Sim, K.M., 2003. Conodurine, conoduramine, and ervahanine derivatives from Tabernaemontana corymbosa. Phytochemistry 63, 625–629. Kam, T.S., Sim, K.M., Pang, H.S., 2003a. New bisindole alkaloids from Tabernaemontana corymbosa. J. Nat. Prod. 66, 11–16. Kam, T.S., Pang, H.S., Lim, T.M., 2003b. Biologically active indole and bisindole alkaloids from Tabernaemontana divaricate. Org. Biomol. Chem. 1, 1292–1297. Knox, J., Slobbe, J., 1975. Indole alkaloids from Ervatamia orientalis. II. The constitution of the ervatamine group. Aust. J. Chem. 28, 1825–1841. Kunesch, N., Das, B.C., Poisson, J., 1967a. Voacanga alkaloids. 7. Structure of voaphylline. Bull. Soc. Chim. Fr., 2155–2160 Kunesch, N., Das, B.C., Poisson, J., 1967b. Hydroxy-indolenine of voaphylline a new alkaloid extracted from the leaves of Voacanga africana Stapf. Bull. Chim. Fr., 3551–3552 Ladhar, F., Damak, M., Ahond, A., Poupat, C., Potier, P., Moretti, C., 1981. Study of American Tanbernaemontana. III. Alkaloids from Anartia cf. meyeri. J. Nat. Prod. 1981 (44), 459–465.

Liang, S., Chen, H.S., Jin, Y.S., Jin, L., Lu, J., Du, J.L., 2007. Study on chemical constituents in rhizome of Ervatamia hainanensis. China J. Chin. Mater. Med. 32, 1296–1299. Ma, K., Wang, J.S., Luo, J., Yang, M.H., Kong, L.Y., 2014. Tabercarpamines AJ, apoptosis-inducing indole alkaloids from the leaves of Tabernaemontana corymbosa. J. Nat. Prod. 77, 1156–1163. Mosmann, T., 1983. Rapid colorimetric assay for cellular growth and survivalapplication to proliferation and cytotoxicity assays. J. Immunol. Methods 65, 55–63. Nugroho, A.E., Hirasawa, Y., Kawahara, N., Goda, Y., Awang, K., Hadi, A.H.A., Morita, H., 2009. Bisnicalaterine A, a vobasine–vobasine bisindole alkaloid from Hunteria zeylanica. J. Nat. Prod. 72, 1502–1506. Okuyama, E., Gao, L., Yamazaki, M., 1992. Analgesic components bornean medicinal plants, Tabernaemontana pauciflora Blume and Tabernaemontana pandacaqui Poir. Chem. Pharm. Bull. 40, 2075–2079. Saxton, J.E., 1995. Recent progress in the chemistry of the monoterpenoid indole alkaloids. Nat. Prod. Rep. 12, 385–411. Sharma, P., Cordell, G.A., 1988. Heyneanine hydroxyindolenine, a new indole alkaloid from Ervatamia coronaria var. plena. J. Nat. Prod. 51, 528–531. Sroll, A., Hofmann, A., 1953. Sarpagin, ein neues alkaloid aus Rauwolfia serpentina Benth. Helv. Chim. Acta 36, 1143–1147. Tanaka, H., Matsushima, H., Nishibu, A., Clausen, B.E., Takashima, A., 2009. Dual therapeutic efficacy of vinblastine as a unique chemotherapeutic agent capable of inducing dendritic cell maturation. Cancer Res. 69, 6987–6994. VanBeek, T.A., Verpoorte, R., Svendsen, A.B., Leeuwenberg, A.J.M., Bisset, N.G., 1984. Tabernaemontana L. (Apocynaceae): a review of its taxonomy, phytochemistry, ethnobotany and pharmacology. J. Ethnopharmacol. 10, 1–156. Wenkert, E., Hagaman, E.W., Wang, N.Y., Kunesch, N., 1979. The C(7) stereochemistry of the chloroindolenines of cleavamines and quebrachamines. Heterocycles 12, 1439–1443.

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Cytotoxic indole alkaloids from Tabernaemontana officinalis.

Continued interest in cytotoxic alkaloids resulted in the isolation of 37 alkaloids including 29 known monoterpenoid indole alkaloids from the aerial ...
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