Note pubs.acs.org/jnp
Alkaloids from the Deep-Sea-Derived Fungus Aspergillus westerdijkiae DFFSCS013 Jiang Peng,†,‡ Xiao-Yong Zhang,† Zheng-Chao Tu,§ Xin-Ya Xu,† and Shu-Hua Qi*,† †
Key Laboratory of Marine Bio-resources Sustainable Utilization/Guangdong Key Laboratory of Marine Material Medical/RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, People’s Republic of China ‡ Graduate School of the Chinese Academy of Sciences (University of Chinese Academy of Sciences), Beijing 100049, People’s Republic of China § Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 190 Kaiyuan Road, Guangzhou 510530, People’s Republic of China S Supporting Information *
ABSTRACT: Two new benzodiazepine alkaloids, circumdatins K and L (1, 2), two new prenylated indole alkaloids, 5-chlorosclerotiamide (3) and 10-epi-sclerotiamide (4), and one novel amide, aspergilliamide B (5), together with six known alkaloids were isolated from the deep-sea-derived fungus Aspergillus westerdijkiae DFFSCS013. Their structures were elucidated by extensive spectroscopic analysis. All of the compounds were tested for cytotoxicity toward human carcinoma A549, HL-60, K562, and MCF-7 cell lines.
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n recent years, deep-sea microorganisms have been uncovered as a new resource for drug lead compounds with the development of methods for sampling, identification, and successful culturing technologies.1,2 However, until now, only a limited number of metabolites have been isolated from truly deep-sea fungi.2,3 A previous study showed that the fungus Aspergillus westerdijkiae produces various metabolites such as the aspergamides, asperloxins, circumdatins (A−G), ochratoxins (A and B), and xanthomegnins (xanthomegnin, viomellein, and vioxanthin).4 During the course of our ongoing search for novel and bioactive compounds from deep-sea-derived fungi, we investigated the chemical constituents of a fermentation medium of the fungal strain A. westerdijkiae DFFSCS013 isolated from a deep-sea sediment sample of the South China Sea (N 19°41.569′, E 119°44.263′; 2918 m depth), which led to the isolation of two new benzodiazepine alkaloids, circumdatins K and L (1, 2), two new prenylated indole alkaloids, 5-chlorosclerotiamide (3) and 10-epi-sclerotiamide (4), and one novel amide, aspergilliamide B (5), together with six known alkaloids, (+)-circumdatin F (6),5,6 circumdatin G (7),7 sclerotiamide (8),8 notoamide C,9 notoamide I,10 and cyclo-L-tryptophanyl-L-proline.11 All the compounds were tested for cytotoxicity toward human carcinoma A549, HL60, K562, and MCF-7 cell lines. Compound 1 (circumdatin K) was obtained as a pale yellow, amorphous solid. Its molecular formula of C16H11N3O3 was determined by HRESIMS. The 1H NMR spectrum (Table 1) revealed the presence of one methylene at δH 4.21 (1H, dd, J = 15.0, 5.0 Hz) and 4.06 (1H, dd, J = 15.0, 7.0 Hz), two exchangeable protons at δH 9.01 (1H, t, J = 5.0 Hz) and 10.05 © XXXX American Chemical Society and American Society of Pharmacognosy
(1H, s), and seven aromatic protons at δH 7.80 (1H, dd, J = 7.5, 1.0 Hz), 7.67 (1H, td, J = 7.5, 1.5), 7.62 (1H, d, J = 7.0 Hz), 7.61 (1H, d, J = 8.0 Hz), 7.60 (1H, td, J = 7.0, 1.5), 7.42 (1H, t, J = 8.0 Hz), and 7.28 (1H, dd, J = 8.0, 1.0 Hz). The 13C NMR spectrum (Table 1) revealed the presence of 16 carbons including one methylene (δC 46.0), seven low-field methines (δC 130.6, 129.2, 128.6, 128.4, 127.9, 119.4, 116.5), and eight low-field quaternary carbons (δC 167.0, 160.9, 152.9, 152.8, 134.9, 133.4, 130.6, 121.9) (Table 1). These data showed great similarity to those of 77 and sclerotigenin,12 and the only obvious differences between 1 and 7 were the lack of one methyl (δC 15.1, δH 1.72 in 7) and one methine (δC 51.3, δH 4.41 in 7) and the additional appearance of one methylene (δC Received: February 15, 2013
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dx.doi.org/10.1021/np400132m | J. Nat. Prod. XXXX, XXX, XXX−XXX
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Table 1. 1H and 13C NMR Spectroscopic Data for 1 and 2 (500 and 125 MHz, respectively, in DMSO-d6, δ ppm) circumdatin K (1) position
δC, mult.
1-NH 2 3 4
167.0, C 130.6, C 129.2, CH
5
128.6, CH
6
128.4, CH
7 8 10 11 12 13
130.6, 133.4, 160.9, 121.9, 116.5, 127.9,
14
119.4, CH
15 15-OH 16 17 18 19
152.9, C
20 21
δH (J in Hz)
circumdatin L (2) δC, mult.
9.01, t (5.5)
CH C C C CH CH
7.80, dd (7.5, 1.0) 7.60, td (7.0, 1.5) 7.67, td (7.5, 1.5) 7.62, d (7.0)
7.61, d (8.0) 7.42, t (8.0) 7.28, dd (8.0, 1.0)
unsaturation, it was reasonable to deduce the presence of an oxepin framework. The characteristic coupling constants of four olefin protons [δH 6.64 (d, J = 11.0 Hz, H-12), 6.23 (dd, J = 11.0, 5.5 Hz, H-13), 5.82 (dd, J = 5.5, 5.5 Hz, H-14), 6.25 (d, J = 5.5 Hz, H-15)] and the COSY spectrum (Figure 1) showing correlations of H-13 with H-12/H-14 and of H-14 with H-13/ H-15 indicated the four protonated sp2 carbons formed a conjugated diene unit. Therefore, the oxygen might attach at C11 or C-17. Correlations of H-12 with C-10, H-13 with C-11, and H-15 with C-17 in the HMBC spectrum of 2 (Figure 1) confirmed that the oxygen attached at C-17. The oxepin framework was also present in the revised structures of circumdatins A and B,13 and the NMR data of the oxepin framework in these compounds were in accord with those of 2, which further confirmed the structure of 2. The specific rotation value of 2 ([α]20D −182) was similar to those of 7 ([α]20D −21.7),7 circumdatin C ([α]20D −75),14 (−)-circumdatin F ([α]20D −55),5 and circumdatin I ([α]20D −236),15 which suggested that these compounds had the same S absolute configuration. The similar CD curves of 2 and 7 further support this conclusion (Figure 2). Compound 3 (5-chlorosclerotiamide) was isolated as a white, amorphous solid, and its molecular formula was found to be C26H28ClN3O5 on the basis of HRESIMS (m/z 498.1778 [M + H]+). The presence of one chlorine atom was deduced from the ca. 3:1 ratio of isotopic peak intensities at m/z 498.1778 [M + H]+ and 500.1762 [M + H + 2]+ in the HRESIMS spectrum. The 1H NMR spectrum (Table 2) showed four methyl signals at δH 0.70 (3H, s), 0.78 (3H, s), and 1.42 (6H, s), one oxymethine proton at δH 5.19 (1H, d, J = 7.5 Hz), three olefin protons at δH 5.84 (1H, d, J = 10.0 Hz), 6.54 (1H, d, J = 10.0 Hz), and 6.91 (1H, s), one OH proton at δH 5.65 (1H, d, J = 8.0 Hz), and two NH protons at δH 8.01 (1H, s) and 10.81 (1H, s). The 13C NMR and DEPT spectra (Table 2) displayed the presence of 26 carbons, including four methyls, four highfield methylenes, one high-field methine (δC 54.9), one oxymethine (δC 72.9), five quaternary carbons, eight olefin carbons, and three carbonyl groups. These data showed great similarity to those of 8,8 except for the absence of one aromatic proton and one corresponding aromatic methine and the presence of one aromatic quaternary carbon in 3. Combined with the molecular formula of 3, these data suggested that one aromatic proton should be substituted by one chlorine atom in 3. The chlorine atom was placed on C-5, which was inferred from the presence of H-4 (δH 6.91) as a singlet and the HMBC spectrum showing correlations of H-4 with C-3/C-5/C-6/C-8. All protons and carbons of 3 were completely assigned by HSQC, HMBC, and COSY spectra. The relative configuration of 3 was deduced by analysis of the NOESY spectrum (Figure 3). NOE correlations between H-4, H-10, and CH3-24 suggested that H-10 and CH3-24 were on the face of the cyclopentane ring that oriented them toward H-4, fixing the relative configuration at C-3 as shown. Correlations of H-19 with NH-21/CH3-23 suggested αorientations of H-19 and CH3-23. Its relative configuration was the same as that of 8 according to their identical NOE data. The specific rotation value of 8 ([α]20D −88) was similar to the literature value of sclerotiamide ([α]20D −55.1), and the absolute configuration of sclerotiamide had been proposed by analogy to a semisynthetic paraherquamide analogue.8 Therefore, on the basis of biogenetic considerations, the absolute configuration of 3 is proposed as 3R,10S,11R,17S,19S.
δH (J in Hz) 8.78, d (5.5)
166.1, C 130.8, C 128.7, CH
7.78, d (7.5)
128.2, CH
7.59, t (7.5)
130.3, CH
7.67, td (7.5, 1.5) 7.60, d (7.5)
129.0, 132.0, 161.3, 110.7, 125.3, 128.1,
CH C C C CH CH
117.2, CH 143.3, CH
6.64, d (11.0) 6.23, dd (11.0, 5.5) 5.82, dd (5.5, 5.5) 6.25, d (5.5)
10.05, s 134.9, C 161.2, C 152.8, C 46.0, CH2
4.21, dd (15.0, 5.0) 4.06, dd (15.0, 7.0)
161.6, C
49.0, CH 14.0, CH3
4.23, m 1.39, d (7.0)
46.0, δH 4.21, 4.06) in 1, which suggested that one proton of the methylene was not substituted by a methyl group in 1. This suggestion was proved by the HMBC spectrum (Figure 1), showing correlations of H-19 with C-2/C-18 and of NH (δH 9.01) with C-3/C-19. All protons and carbons of 1 were completely assigned by HSQC and HMBC spectra.
Figure 1. Key HMBC and COSY correlations of 1 and 2.
Compound 2 (circumdatin L) was obtained as a light yellow, amorphous solid. The molecular formula was established as C17H13N3O3 by HRESIMS. The 1H and 13C NMR data (Table 1) showed similarity to those of 65,6 and 7.7 However, the signals of four olefin protons at δH 5.8−6.7 in 2 were distinctly different from benzene proton signals (H-12, -13, -14, -15) at δH 7.6−8.2 in 6, and differences were also observed in the 13C NMR spectrum (Table 1). The A−B−C ring substructure in 2 was readily assembled by comparison of the 1H and 13C NMR data of 2 and 6 and analysis of the HSQC, HMBC, and COSY spectra of 2 (Figure 1). Four protonated sp2 carbons and one oxygen remained to be assigned. Referring to the degree of B
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Figure 2. CD spectra of 2, 6, and 7.
5b. Unfortunately, the configurations of C-3 and the oxime were not determined. Compound 6 [(+)-circumdatin F] was afforded as a white, amorphous solid. The NMR data of 6 were in accordance with those of circumdatin F.5,6 However, the specific rotation value of 6 ([α]20D +135) was opposite the reported value for synthetic S-(−)-circumdatin F ([α]20D −55),5 which suggested that 6 was the R-(+)-isomer of circumdatin F. This suggestion was further supported by comparing the CD spectrum of 6 with those of 2 and 7 (Figure 2). No specific rotation was reported for the original isolate of circumdatin F.6 Unexpectedly, the R configuration of 6 was opposite compared to those of other benzodiazepine alkaloids such as circumdatins C, F, G, and I. Circumdatins C, F, G, and I appear to be biosynthesized from two appropriately substituted anthranilic acid units and Lalanine,5 but as for 6, it might be biosynthesized from two anthranilic acid units and D-alanine. None of the compounds isolated from A. westerdijkiae DFFSCS103 showed cytotoxicity toward the human carcinoma A549, HL-60, K562, and MCF-7 cell lines (IC50 >10 μm). The IC50 values determined for compounds 3 (44 μm) and 4 (53 μm) in the K562 cell line and for compound 8 (26 and 45 μm) in the K562 and HL-60 cell lines, respectively, were similar to those reported for the related compounds notoamides C9 and I.10
Compound 4 (10-epi-sclerotiamide) was isolated as a white, amorphous solid. It had the same molecular formula (C26H29N3O5) as 8, which was determined by HRESIMS. The 1H and 13C NMR spectral data of 4 (Table 2) showed great similarity to those of 8,8 except for the chemical shift differences of CH-10 (δC 77.5, δH 4.62 in 4 and δC 73.9, δH 5.38 in 8) and C-3 (δC 65.7 in 4 and δC 70.1 in 8). Extensive analysis of the 1H NMR, 13C NMR, HSQC, and HMBC spectra of 4 implied the same planar structure as for 8. The relative configuration of 4 was established by analysis of the NOESY spectrum (Figure 3). NOE correlations of 10-OH with H-4/H5/CH3-24 suggested that OH-10 and CH3-24 were β-oriented, while NOE interactions between H-10, H-19, NH-21, and CH3-23 suggested the α-orientation of H-10, H-19, and CH323. These data indicated that 4 was an isomer of 8 at C-10 and was therefore named 10-epi-sclerotiamide. Compound 5 (aspergilliamide B) was afforded as a white, amorphous solid. It had the molecular formula C11H20N2O4, as inferred from HRESIMS. The 1H NMR spectrum showed three exchangeable protons at δH 11.78 (1H, s), 7.26 (1H, s), and 7.11 (1H, s), one oxymethine at δH 5.53 (1H, d, J = 9.0 Hz), two methines at δH 2.46 (1H, m) and 1.99 (1H, m), one methylene at δH 2.15 (2H, d, J = 7.0 Hz), and four methyls at δH 0.98 (3H, d, J = 7.0 Hz), 0.89 (6H, d, J = 6.5 Hz), and 0.82 (3H, d, J = 6.5 Hz). The 13C NMR spectrum indicated the presence of two carbonyl groups (δC 171.4, 164.3), one quaternary carbon (δC 150.2), one oxymethine (δC 71.6), two methines (δC 29.1, 25.0), one methylene (δC 42.4), and four methyls (δC 21.9, 21.9, 19.0, 17.9). These NMR data were similar to those of aspergilliamide (9),16 which was also isolated from an Aspergillus species, except for the presence of one oxymethine and the absence of one methylene. In the HMBC spectrum (Figure 4), correlations from H-8 to C-7/C-9/C-10/ C-11 suggested the existence of the 5a unit. HMBC correlations from H-3 to C-1/C-2/C-4, from CH3-6 to C-3/ C-4/C-5, and from oxime −OH and acylamino −NH2 to C-2 indicated the presence of the 5b unit. Furthermore, an HMBC correlation from H-3 to C-7 confirmed the connection of 5a to
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EXPERIMENTAL SECTION
General Experimental Procedures. Optical rotations were measured with an Anton Paar MCP 500 polarimeter. UV spectra were obtained using a Shimadzu UV-2600 UV−vis spectrophotometer. CD spectra were measured with a Chirascan circular dichroism spectrometer (Applied Photophysics). IR spectra were measured with a Shimadzu IRAffinity-1 Fourier transform infrared spectrophotometer. 1H/13C NMR and 2D NMR spectra were recorded on a Bruker AV-500 MHz NMR spectrometer with TMS as an internal standard. HRESIMS spectra were measured on a Bruker microTOF-QII mass spectrometer. Semipreparative reversed-phase (SP-RP) HPLC utilized a Shimadzu LC-20AT pump with a Shimadzu SPD-M20A photodiode array detector using a Phenomenex Gemini 5 μ C18 110A column (250 × 10 mm, 5 μm). Column chromatography (CC) was performed on C
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Table 2. 1H and 13C NMR Spectroscopic Data for 3 and 4 (500 and 125 MHz, respectively, in DMSO-d6, δ ppm) 5-chlorosclerotiamide (3) position 1-NH 2 3 4 5 6 7 8 9 10 10-OH 11 12 14
δC, mult. 177.4, 69.0, 125.2, 112.0, 147.7, 105.3, 138.1, 122.1, 72.9,
C C CH C C C C C CH
65.3, C 168.6, C 43.2, CH2 24.2, CH2
16
28.8, CH2
17 18
68.4, C 29.5, CH2
19
54.9, CH
a
10-epi-sclerotiamide (4) δC, mult.
10.81, s
15
20 21-NH 22 23 24 25 26 27 28 29
δH (J in Hz)
6.91, s
5.19, d (7.5) 5.65, d (8.0)
3.41, t (6.0) 2.03, m 1.84a 2.54, m 1.84a 1.96, dd (10.0, 12.5) 1.77, dd (9.5, 12.5) 3.76, t (9.5)
172.5, C
182.6, 65.7, 129.0, 107.8, 151.9, 104.4, 138.8, 118.4, 77.5,
C C CH CH C C C C CH
64.1, C 171.5, C 42.9, CH2 24.0, CH2 28.1, CH2 67.9, C 28.3, CH2
51.9, CH
C CH3 CH3 CH CH C CH3 CH3
7.03, d (8.0) 6.38, d (8.0)
Figure 4. Key HMBC correlations of 5.
EF661428). The BLAST sequenced data have been deposited at GenBank (accession no. JX156359). The strain was deposited in the RNAM Center, South China Sea Institute of Oceanology, Chinese Academy of Sciences. Fermentation and Extraction. Fermentation of the strain was carried out in 5000 mL Erlenmeyer flasks containing solid rice medium (each flask contained 400 g of commercially available rice, 2.0 g of yeast extract, 2.0 g of glucose, 18.0 g of sea salt, and 600 mL of water). The fungal strain from a culture plate was inoculated in 500 mL Erlenmeyer flasks, each containing 150 mL of potato dextrose broth supplemented with 3% sea salt. Flask cultures were incubated at 26 °C on a rotary shaker at 200 rpm for 2 days as seed cultures. Then, each of the seed cultures (50 mL) was transferred into autoclaved 5000 mL Erlenmeyer flasks that contained solid rice medium. After that, the flasks were incubated at 26 °C as static cultures for 26 days. The total 2 kg of rice culture was crushed and extracted with 80% acetone three times. The acetone extract was evaporated under reduced pressure to afford an aqueous solution, and then the aqueous solution was extracted with EtOAc to yield 30 g of a crude gum. Isolation and Purification. The extract was subjected to silica gel CC using gradient elution with a CHCl3/MeOH solvent system at the ratios of 100:0, 98:2, 95:5, 90:10, 80:20, 50:50, and 0:100 (v/v) to give eight fractions (Fr.1−Fr.8). Fr.2 was purified repeatedly by silica gel CC, eluting with CHCl3/(CH3)2CO at ratios of 50:1, 20:1, 10:1, 4:1, and 2:1 (v/v) to afford Fr.2-1−Fr.2-7. Fr.2-3 was isolated by MPLC with an ODS column, eluting with MeOH/H2O (from 30:70 to 90:10, 90 min, 20 mL/min) to give Fr.2-3-1−Fr.2-3-9. Fr.2-6 was also isolated by MPLC with an ODS column, eluting with MeOH/H2O (from 30:70 to 100:0, 90 min, 20 mL/min), to give Fr.2-6-1−Fr.2-6-5. Fr.2-6-2 was purified by SP-RP HPLC, eluting with MeOH/H2O (40:60), to afford 2 (tR = 16.0 min, 2.5 mg). Fr.3 was chromotographed on a Sephadex LH-20 column eluting with CHCl3/MeOH (1:1) to offer Fr.3-1−Fr.3-4. Fr.3-3 was subjected to ODS CC eluting with MeOH/H2O (from 30:70 to 90:10, 90 min) to afford Fr.3-3-1− Fr.3-3-7. Fr.3-3-2 was further purified by SP-RP HPLC with MeOH/ H2O (30:70) to give 1 (tR = 37.0 min, 2.8 mg) and cyclo-Ltryptophanyl-L-proline (tR = 29.0 min, 7.0 mg). Fr.3-3-3 was purified by SP-RP HPLC with MeOH/H2O (40:60) to give 7 (tR = 28.0 min, 2.4 mg). Fr.3-3-4 was purified by a Sephadex LH-20 column eluting with CHCl3/MeOH (1:1) to give 6 (2.0 mg). Fr.3-3-6 was purified by SP-RP HPLC with MeOH/H2O (60:40) to yield notoamide C (tR = 25.0 min, 11.2 mg). Fr.4 was chromatographed repeatedly by silica gel CC eluting with CHCl3/(CH3)2CO at the ratios 9:1, 8:2, 7:3, 5:5, and 0:10 (v/v) to afford Fr.4-1−Fr.4-10. Fr.4-5 was purified by SP-RP HPLC with MeOH/H2O (55:45) to yield 5 (tR = 22.0 min, 1.9 mg). Fr.4-6 was purified by SP-RP HPLC with MeOH/H2O (50:50) to yield notoamide I (tR = 26.0 min,7.0 mg). Fr.4-8 was subjected to ODS CC eluting with MeOH/H2O at ratios of 50:50 and 70:30 (v/v) to afford Fr.4-8-1−Fr.4-8-3. Fr.4-8-3 was purified by SP-RP HPLC with MeOH/H2O (65:35) to yield 3 (tR = 25.0 min, 2.0 mg), 8 (tR = 30.0 min, 20.0 mg), and 4 (tR = 33.0 min, 2.5 mg). Circumdatin K (1): pale yellow, amorphous solid; UV (MeOH) λmax (log ε) 203 (4.46), 235 (4.08), 275 (3.46), 329 (4.42) nm; IR (CHCl3) νmax 3412, 3178, 2928, 2860, 1661, 1645, 1618, 1582, 1466, 1356, 1290, 1230 cm−1; 1H and 13C NMR spectroscopic data, see
4.62, d (10.5) 6.27, d (11.0)
3.45, m 3.40, m 2.04, m 1.86a 2.00, m 1.83a 2.50a
2.68, dd (20.0, 7.0)
172.5, C 8.01, s
43.1, 22.5, 18.9, 116.2, 130.8, 77.1, 27.5, 27.5,
δH (J in Hz) 10.68, s
0.70, 0.78, 6.54, 5.84,
s s d (10.0) d (10.0)
1.42, s 1.42, s
9.48, s 43.6, 25.1, 21.0, 116.6, 129.8, 75.6, 27.5, 27.5,
C CH3 CH3 CH CH C CH3 CH3
0.82, 0.82, 6.59, 5.74,
s s d (10.0) d (10.0)
1.38, s 1.36, s
Signals overlapping.
Figure 3. Key NOESY correlations of 3 and 4. silica gel (200−300 mesh, Qingdao Marine Chemical), Sephadex LH20, or Rp-18 silica (Pharmacia Co. ODS). Fungal Material. The fungal strain DFFSCS013 was isolated from a marine sediment sample collected in the South China Sea (N 19°41.569′, E 119°44.263′; 2918 m depth) in August 2011. The strain DFFSCS013 was identified as Aspergillus westerdijkiae based on a molecular biological protocol calling for DNA amplification and ITS region sequence comparison with the GenBank database and shared a similarity of 99% with A. westerdijkiae NRRL 5175 (accession no. D
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Table 1; (+)-HRESIMS m/z 294.0862 [M + H]+ (calcd for C16H12N3O3, 294.0873). Circumdatin L (2): light yellow, amorphous solid; [α]20D −182 (c 0.25, CHCl3); UV (CHCl3) λmax (log ε) 207 (4.53), 235 (4.53), 343 (3.55) nm; CD (9.772 mM, CHCl3) λmax (Δε) 240 (−0.17), 255 (0.04), 277 (−0.33), 328 (−0.12); IR (CHCl3) νmax 3198, 1666, 1584, 1543, 1454, 1389, 1309 cm−1; 1H and 13C NMR spectroscopic data, see Table 1; (+)-HRESIMS m/z 308.1027 [M + H]+ (calcd for C17H14N3O3, 308.1030). 5-Chlorosclerotiamide (3): white, amorphous solid; [α]20D −74 (c 0.35, MeOH); UV (MeOH) λmax (log ε) 199 (4.69), 244 (4.37), 328 (3.31) nm; IR (MeOH) νmax 3281, 2943, 2829, 1668, 1393 cm−1; 1H and 13C NMR spectroscopic data, see Table 2; (+)-HRESIMS m/z 498.1778 [M + H]+ (calcd for C26H29ClN3O5, 498.1790). 10-epi-Sclerotiamide (4): white, amorphous solid; [α]20D −41 (c 0.35, MeOH); UV (MeOH) λmax (log ε) 200 (4.65), 246 (4.38), 318 (3.15) nm; IR (MeOH) νmax 3314, 2943, 2832, 1672, 1643, 1448, 1309 cm−1; 1H and 13C NMR spectroscopic data, see Table 2; (+)-HRESIMS m/z 464.2166 [M + H]+ (calcd for C26H30N3O5, 464.2180). Aspergilliamide B (5): white, amorphous solid; [α]20D −14 (c 0.16, MeOH); UV (MeOH) λmax (log ε) 199 (4.33) nm; IR (MeOH) νmax 3287, 2943, 2830, 1666, 1447, 1402, 1309 nm; 1H NMR (DMSO-d6, 500 MHz) δH 11.78 (1H, s, −OH), 7.26 (1H, s, −NH), 7.11 (1H, s, −NH), 5.53 (1H, d, J = 9.0 Hz, H-3), 2.46 (1H, m, H-4), 2.15 (2H, d, J = 7.0 Hz, CH2-8), 1.99 (1H, m, H-9), 0.98 (3H, d, J = 7.0 Hz, CH35), 0.89 (6H, d, J = 6.5 Hz, CH3-10, CH3-11), 0.82 (3H, d, J = 6.5 Hz, CH3-6); 13C NMR (DMSO-d6, 125 MHz) 171.4 (C-7), 164.3 (C-1), 150.2 (C-2), 71.6 (C-3), 42.4 (C-8), 29.1 (C-4), 25.0 (C-9), 21.9 (C10, C-11), 19.0 (C-5), 17.9 (C-6); (+)-HRESIMS m/z 245.1493 [M + H]+ (calcd for C11H21N2O4, 245.1496). R-(+)-Circumdatin F (6): white, amorphous solid; [α]20D +135 (c 0.85, CHCl3) [lit.5 S-(−)-circumdatin F: [α]20D −55 (c 0.94, CHCl3)]; CD (0.515 mM, CHCl3) λmax (Δε) 238 (3.59), 256 (−6.41), 312 (1.77). Circumdatin G (7): white powder; [α]20D −165 (c 0.37, CHCl3/ MeOH, 1:1) [lit.7 [α]20D −21.7 (c 0.19, MeOH)]; CD (0.489 mM, CHCl3) λmax (Δε) 232 (−2.95), 251 (0.43), 275 (−1.78), 328 (−0.64). Sclerotiamide (8): white, amorphous solid; [α]20D −88 (c 0.9, MeOH) [lit.8 [α]20D −55.1 (c 0.1, MeOH)]. Cytotoxicity Assay. Cytotoxic activity was evaluated using human erythroid leukemic K562, promyelocytic leukemia HL-60, breast adenocarcinoma MCF-7, and lung carcinoma A549 cell lines by the MTT method as described previously.17
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Note
REFERENCES
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ASSOCIATED CONTENT
S Supporting Information *
This material (1H, 13C NMR, DEPT, HSQC, HMBC, COSY, NOESY, and HRESIMS spectroscopic data for compounds 1− 5) is available free of charge via the Internet at http://pubs.acs. org.
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AUTHOR INFORMATION
Corresponding Author
*Tel: (86) 20-89022112. E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors are grateful to the National High Technology Research and Development Program of China (863 Program, grant 2012AA092104), National Basic Research Program of China (973 Program, grant 2010CB833803), National Marine Public Welfare Research Project of China (grant 201305017), and Science and Technology Foundation of Guangdong Province (grant 2010B030600009) for financial support. E
dx.doi.org/10.1021/np400132m | J. Nat. Prod. XXXX, XXX, XXX−XXX
