Indole Alkaloids from Chaetomium globosum

Jun 30, 2015 - Chaetomium globosum. Their structures were elucidated by spectral analysis. Three new epipolythiodioxopiperazines, chaetocochins G−I ...
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Indole Alkaloids from Chaetomium globosum Guo-Bo Xu,†,‡ Gu He,§ Huan-Huan Bai,† Tao Yang,† Guo-Lin Zhang,† Lin-Wei Wu,† and Guo-You Li*,† †

Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, People’s Republic of China ‡ School of Pharmacy, Guiyang Medical College, Guiyang, Guizhou 550004, People’s Republic of China § State Key Laboratory of Biotherapy/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, People’s Republic of China S Supporting Information *

ABSTRACT: Two new indole alkaloids chaetocochin J (1) and chaetoglobinol A (8), along with chetomin (2), chetoseminudin A (3), cochliodinol (9), and semicochliodinol (10), were isolated from the rice culture of the fungus Chaetomium globosum. Their structures were elucidated by spectral analysis. Three new epipolythiodioxopiperazines, chaetocochins G−I (5−7), were identified by the combination of UPLC and mass spectrometric analysis. Chaetocochin I contained two sulfur bridges, one formed by three sulfur atoms between C-3 and C-11a, and the other formed by four sulfur atoms between C-3′ and C-6′. Chaetocochin I was readily transformed into chetomin (2), chetoseminudin A (3), chaetocochin D (4), chaetocochin G (5), and chaetocochin H (6) by losing sulfur atoms. Compounds 1−3, and 8 exhibited antibacterial activities against Bacillus subtilis with MICs of 25, 0.78, 0.78, and 50 μg/mL, respectively, but not against Gram-negative bacterium (Escherichia coli). Compounds 2 and 8 were inactive against Candida albicans, Fusarium graminearum, Fusarium vasinfectum, Saccharomyces cerevisiae, and Aspergillus niger even at the high concentrations of 200 and 100 μg/mL, respectively. Compound 8 showed free radical scavenging capacity against the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid radical (ABTS+•), with IC50 values of 143.6 and 45.2 μM, respectively. The free radical scavenging capacity rates of compounds 1−3 on the DPPH and ABTS+• were less than 20% at the test concentrations (89.9−108.3 μM). The superoxide anion radical scavenging assay indicated that compounds 1−3, and 8 showed 14.8% (90.9 μM), 18.1% (90.9 μM), 51.5% (88.3 μM), and 30.4% (61.3 μM) superoxide anion radical scavenging capacity, respectively.

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antifungal activity, have been reported from Chaetomium.12,17,20−28 Mycotoxins represent a diverse group of secondary fungal metabolites that have attracted the attention of microbiologists and pharmacologists for some time because of the acute and lethal toxicity.29 Many mycotoxins, including aflatoxins, trichothecene, ochratoxin, and ergot alkaloids, possess extreme toxicity, and their presence is strictly regulated in food and feedstuffs.30,31 Some fungal metabolites have been developed into important pharmaceuticals; these include penicillin, cyclosporin A, and lovastatin. In our search for bioactive molecules from the genus Chaetomium, six compounds (1−3 and 8−10) were isolated from the active ethyl acetate extract of Chaetomium globosum which inhibited the growth of Bacillus subtilis at 20.0 μg/mL. Meanwhile, compounds 4−7 were identified by the combination of UPLC and mass spectrometric analysis from the same extract. Compounds 1 and 5−8 are new indole alkaloids.

he genus Chatomium is well-known for producing structurally diverse and complex natural products with either toxicity against pathogens or harmful effects to plants, animals, and human beings. At present, about 400 species of Chaetomium have been recorded in the Index Fungorum,1 and some of these species exhibit promising antagonistic activity against agricultural pathogens such as Pythium ultimum, Rhizoctonia solani, Alternaria brassicicola, Botrytis cinerea, Cochliobolus sativus, Venturia inaequalis, Drechslera oryzae, and Fusarium oxysporum sp. lycopersici.2−11 Antibiosis is one of the antagonism mechanisms of Chaetomium sp. against pathogens. Their secondary metabolites, such as chetomin and chaetoglobosin C, play important roles in the antagonism against many pathogens.7,8 Some Chaetomium fungi are pathogenic to plants, animals, and humans, and may cause phaeohyphomycosis, onychomycosis, allergy, orphytotoxicity, and lethality.12−16 There is little doubt that secondary metabolites are one key factor in the pathogenicity of Chaetomium.17−19 Over 200 metabolites with diverse bioactivities, including cytotoxicity, phytotoxicity, enzyme inhibitory, nematicidal, antibacterial, and © XXXX American Chemical Society and American Society of Pharmacognosy

Received: September 16, 2014

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Compounds 1−3 and 8 showed antimicrobial activities against B. subtilis, but were not active against Candida albicans, Fusarium graminearum, Fusarium vasinfectum, Saccharomyces cerevisiae, Aspergillus niger, and Escherichia coli (antifungal activities only for compounds 2 and 8). The antioxidative activities of compounds (1−3, and 8) were also evaluated by DPPH free radical assay, ABTS cation radical assay, and superoxide anion radical assay. Here, we report the isolation, identification, analysis, and the bioactivities of the metabolites from C. globosum.

Compound 8 was isolated as a yellow powder and assigned the molecular formula C32H30N2O5 based on HR-ESIMS analysis (m/z 521.2073 [M − H]−), with 19 degrees of unsaturation. The IR absorptions at 3400 and 1672 cm−1 suggested the presence of hydroxy and carbonyl groups. On the basis of HSQC experiment, four methyls [δH 1.69 (3H, s), 1.70 (3H, s), 1.74 (3H, s), 1.72 (3H, s); δC 17.9, 17.9, 25.9, 25.9], three carbonyls (δC 195.8, 193.5, 190.0) and an oxygenated quarternary C atom (δC 86.0) were assigned. The 13C NMR data of 8 was partly similar to those of cochliodinol (9) (Table 2); thus, this suggested that compound 8 was an asterriquinone derivative. In the HMBC spectrum, correlations of H-2′/C-3′, C-8′, and C-9′, H-4′/C-3′, C-6′ and C-8′, H-7′/C-9′ and C-5′ confirmed the presence of an indole unit. The dimethylallyl group located at C-5′ was confirmed by the correlations of H-13′/C-12′, C-14′, and C11′, H-11/C-10′, H-10′/C-5′. Another 5″-dimethylallyl indole unit of 8 was verified by the HMBC signals (H-2″/C-3″, C-8″, and C-9″, H-4″/C-3″, C-6″ and C-8″, H-7″/C-9″ and C-5″, H13″/C-12″, C-14″, and C-11″, H-10″/C-5″ and C-12″). In the 13 C NMR spectrum of compound 8, the signals for three carbonyls (δC 195.8, 193.5, 190.0) and an oxygenated quarternary C atom (δC 86.0) were observed, while these were absent in compound 9. The carbonyls resonances (C1, C2, C4, and C5) of 2,5-dihydroxycyclohexa-2,5-diene-1,4-dione in the asterriquinone can only be observed in THF-d8 or in CDCl3 at −75 °C.35 The dioxygenated quinone moiety in compound 9 exists in a form of keto−enol tautomerism (1,2,4,5-tetraone) in solvent. Five degrees of unsaturation must be attributed to a double bond, a ring, and three carbonyls in addition to the 14 contributed by two dimethylallyl substituted indoles in the structure. The central quinone moiety in compound 8 was suggested to be 3,5dihydroxycyclohexa-5-ene-1,2,4-trione. The structure of 8 was finally elucidated as shown in Figure 2. Epipolythiodioxopiperazines with disulfide or polysulfide bridge on the diketopiperazine ring are a class of fungal toxins possessing diverse bioactivities including being ascytotoxin, antimicrobial, and antiviral,36,37 which has attracted the attention of chemists and pharmacologists. We have discovered new cytotoxic ETPs from Chaetomium cochliodes,38 and analyzed the MS fragmentation mechanism of ETPs.34 In this study, the minor ETP metabolites from C. globosum were analyzed by UPLC-MS (see UV spectrum, Figure 3, Schemes1−3). Compounds 2 and 3 were identified to be chetomin and chetoseminudin A, respectively, by comparing the retention time with those of reference substances. The molecular formulas of compounds 4− 7 were successively determined as C 3 1 H 3 0 N 6 O 6 S 5 , C31H30N6O6S6, C31H30N6O6S6, and C31H30N6O6S7 by HRESIMS. Compound 4 was assigned as chaetocochin D based on the fragmentation of McLafferty rearrangements (Scheme 1) and the loss of a sulfur atom from each ring, which was identical with the conclusion reported by Wu. The structures of compounds 5−7 (chaetocochins G−I) were postulated from the mass spectrometric cleavage characteristic of ETPs (Schemes 2 and 3). In the isolation process of 7, which was assigned a molecular formula C31H30N6O6S7 by the HR-ESIMS analysis (m/z 829.0165 [M + Na]+), we found it was unstable and easily converted into chetomin (2), chetoseminudin A (3), chaetocochins D (4), G (5), and H (6), which were determined by UPLC-MS analysis. The known compounds were identified to be chetomin (2),33 chetoseminudin A (3),32 cochliodinol (9),35 and semicochliodinol (10)39 by comparing their NMR data and optical rotation values with those reported.

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RESULTS AND DISCUSSION Compound 1 was obtained as white amorphous powder. Its molecular formula was determined to be C31H30N6O6S4 from the quasimolecular ion peak at m/z 733.1002 [M + Na]+ in HRESIMS, indicative of 20 degrees of unsaturation. The IR spectrum of 1 revealed the presence of hydroxy (3433 cm−1) and carbonyl (1676 cm−1) groups. From the HSQC data, four carbonyls (δC 158.2, 164.4, 168.9, and 168.2) and three Nmethyls (δH 3.02, 3.22, 3.22; each s, 3H; δC 32.2, 30.4, 29.7) were recognized. The 1H and 13C NMR data were very similar to those of chetomin (2) and chetoseminudin A (3) (Table 1) except two more carbon-atom signals (δC 115.8 and 137.3) for a double bond were observed, but one methylene (δC 42.9) and one quarternary (δC 73.8) carbon was missing in the 13C NMR spectrum of 1.32,33 The HMBC correlations of H-11/C-10b (78.3) and C-11a (137.3), and H-5/C-10b revealed that the double bond was located between C11 and C11a. In the mass fragmentation experiment, the ion peak at m/z 605.2147 [M + H − S4]+ (see in the Supporting Information) due to the loss of four sulfur-atoms from the quasi-molecular ion was observed. However, under the same condition of tandem mass spectrometry analysis, Wu et al. reported the loss of two sulfur atoms from chetomin ([M + H − S2]+, 669.1572).34 Thus, these data suggested that four sulfur atoms found in compound 1 formed a bridge between C-3′ and C-6′ on the diketopiperazine ring in 1. In addition, as indicated by the NMR data, the presence of a methine (δH 4.26; δC 67.8, CH-3) and the double bond carbon atom (δC 137.3, C-11a) suggest that there was no sulfur atoms at C-3 and C-11a. Finally, the structure of 1 was elucidated on the basis of HSQC and HMBC correlations. The relative configuration (except C-3) was deduced by NOESY experiments (Figure 1). B

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Table 1. NMR Data of Compounds of 1−3a 1b

a

position

δC, type

1 2-NCH3 3 3-CH2OH 4 5 6a 7 8 9 10 10a 10b 11 11a 1′ 2′-NCH3 3′ 3′-CH2OH

158.2, C 32.2, CH3 67.8, CH 61.4, CH2 164.4, C 83.0, CH 151.4, C 110.7, CH 126.1, CH 120.0, CH 131.1, CH 127.8, C 78.3, C 115.8, C 137.3, C 168.9, C 30.4, CH3 80.0, C 62.6, CH2

4′ 5′-NCH3 6′ 7′

168.2, C 29.7, CH3 79.1, C 31.3, CH2

8′ 9′ 10′a 11′ 12′ 13′ 14′ 14′a

108.5, C 125.8, CH 135.4, C 112.8, CH 123.0, CH 120.8, CH 120.0, CH 130.9, C

2c δH (J/ Hz) 3.02, s 4.26, overlap 4.40, d (11.2) 4.15, overlap 6.41, s 7.03, d (7.8) 7.25−7.20, overlap 6.61, t (7.3) 7.25−7.20, overlap

6.95, overlap

3.22, s 4.77, d (11.3) 4.20, overlap 3.22, s 4.32, d (15.3) 3.70, d (15.3) 7.74, s 7.25−7.20, overlap 6.98, t (7.9) 7.17, t (7.9) 7.85, d (7.9)

3c

δC

δC

167.1 27.6 75.0 61.4 163.4 80.3 148.6 111.4 125.3 120.6 131.7 126.8 76.8 42.9 73.8 165.8 27.3 74.0 60.8

168.6 28.0 75.7 62.4 165.6 79.6 150.0 111.4 125.1 120.6 132.0 126.0 78.5 49.3 72.2 165.9 27.7 75.0 61.5

165.8 27.7 76.3 27.3

167.1 28.5 76.8 27.3

107.9 127.5 134.3 111.6 123.1 120.8 119.4 130.6

108.3 126.9 134.7 111.9 123.1 120.7 119.0 130.4

Assignments based on HSQC and HMBC experiments. bIn pridine-d5; 1H 600 MHz; 13C 150 MHz. cIn CD3Cl; 13C 100 MHz.

Figure 1. Key HMBC and NOESY correlations of compound 1.

test fungal strains at the concentrations up to 200 and 100 μg/ mL, respectively. Antioxidative assays were performed by three methods. Compound 8 showed moderate antioxidative activities on the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and 2,2′-azino-bis-3ethylbenzothiazoline-6-sulfonic acid radical (ABTS+•) scavenging assay models, with IC50 values of 143.6 and 45.2 μM, respectively (vitamin C, IC50 = 0.02 μM, 0.01 μM, respectively). The superoxide anion radical scavenging assay indicated that 8

Two strains of bacteria (E. coli 1.044 and B. subtilis 1.079) and five fungi (C. albicans, F. graminearum, F. vasinfectum, S. cerevisiae, and A. niger) were selected for antibacterial and antifungal assays. Compounds 1−3 showed strong inhibitory activity against B. subtilis 1.079 with MICs values of 25, 0.78, and 0.78 μg/mL (methicillin, MIC = 0.78 μg/mL), respectively. Compound 8 exhibited weak activity against B. subtilis 1.079 (c = 50 μg/mL). However, compounds 1−3, and 8 were not active against E. coli (c = 50 μg/mL). Compounds 2 and 8 were inactive against the C

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Table 2. NMR Data of Compounds 8 and 9a 8b position

δC, type

1, 2, 4

195.8, C; 190.0, C; 193.5, C 86.0, C 162.6, C 131.3, C 137.9, CH 131.3, CH 113.9, C 106.2, C 122.0, CH 123.6, CH 134.6, C 137.0, C 125.2, CH 124.3, CH 112.7, CH 112.4, CH 135.6, C 136.3, C 128.1, C 127.1, C 35.4, CH 35.3, CH 125.3, CH 125.5, CH 132.0, C 132.1, C 25.9, CH3 25.9, CH3 17.9, CH3 17.9, CH3

3 5 6 2′ 2″ 3′ 3″ 4′ 4″ 5′ 5″ 6′ 6″ 7′ 7″ 8′ 8″ 9′ 9″ 10′ 10″ 11′ 11″ 12′ 12″ 13′ 13″ 14′ 14″

9c δH (J/ Hz)

δC

δH (J/ Hz)

111.8

8.73, d (3.2) 8.40, d (2.9)

8.10, s 8.25, s

7.07, dd (8.1, 1.4) 7.05, dd (8.1, 1.2) 7.42, d (8.1) 7.40, d (8.1)

3.38−3.44, overlap 3.38−3.44, overlap 5.34, overlap 5.38, overlap

1.69, s 1.70, s 1.74, s 1.72, s

111.8 127.8 127.8 104.5 104.5 120.8 120.8 131.9 131.9 122.3 122.3 111.8 111.8 135.7 135.7 127.2 127.2 34.7 34.7 125.3 125.3 131.0 131.0 25.9 25.9 18.2 18.2

7.20, s 7.20, s

7.43, d (3.0) 7.43, d (3.0)

6.90, d (8.4) 6.90, d (8.4) 7.30, d (8.4) 7.30, d (8.4)

3.34, overlap 3.34, overlap 5.30, t like 5.30, t like

1.68, overlap 1.68, overlap 1.68, overlap 1.68, overlap

a Assignments based on HSQC and HMBC experiments. bIn acetone-d6. 1H 400 MHz; 13C 100 MHz; NMR data for the two 5-dimethylallyl indole units may be interchangeable. cIn DMSO-d6. 13C 150 MHz.

scavenging rates below 10% at the concentrations of 93.9, 93.9, and 89.9 μM, respectively. The superoxide anion radical scavenging assay displayed that compounds 1−3 possessed superoxide anion radical scavenging capacity of 14.8, 18.1, and 51.5% at concentrations of 90.9, 90.9, and 88.3 μM, respectively. The ABTS+• scavenging assay indicated that compounds 1−3 showed weak antioxidative activities with scavenging rates less than 20% at the concentrations of 108.3, 108.3, and 103.7 μM, respectively.

Figure 2. Key HMBC correlations of compound 8.

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showed 30.4% superoxide anion radical scavenging capacity at 61.3 μM (Cyanidenon, IC50 = 22.3 μM). Compounds 1−3 showed weak antioxidative activities on the DPPH assay with

EXPERIMENTAL SECTION

General Experimental Procedures. High-resolution electrospray ionization mass spectra (HR-ESI-MS) were carried out on a BioTOF-Q

Figure 3. UV-UPLC chromatogram of compounds 2−7 from Fra.D. D

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Scheme 1. Partial Fragmentation Pathways of [M + H]+ for Chaetocochin D (4)

Scheme 2. Partial Fragmentation Pathways of [M + H]+ for Chaetocochins G (5) and H (6)

mass spectrometer. UPLC-MS analysis was performed on a UPLC-TQ mass spectrometer. Optical rotations were measured on a PerkinElmer

341 polarimeter. UV spectra were obtained on a PerkinElmer S2 Lambda 35 UV/vis spectrometer. IR spectra: PerkinElmer Spectrum E

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Scheme 3. Partial Fragmentation Pathways of [M + H]+ for Chaetocochin I (7)

One FT-IR spectrometer; as KBr pieces; in cm−1. NMR spectra were performed on the Bruker Avance 600/400 spectrometers; δ in ppm, J in Hz; residual solvent peak as reference. Thin-layer chromatography (TLC) was executed on silica gel GF254 from Qingdao Haiyang Chemical Co., Ltd. (QHCC), detected under a UV lamp at 254 or 365 nm, and visualized by spraying with 5% sulfuric acid/ethanol (v/v) solution followed by heating. Column chromatography (CC) was performed on columns with silica gel (QHCC), Sephadex LH-20 (Pharmacia), and semipreparative high-performance liquid chromatography with a UV−vis detector and a Kromasil C18 column (250 mm × 10 mm; 5 μm). All solvents were of analytical grade. Fungus Material. C. globosum was isolated from soil collected in Xichang of Sichuan Province, China, and identified by associate Professor Tao Yang (Chengdu Institute of Biology) with the methods of microscopic and macroscopic features, and by Xiang Pu with the method of molecular identification (see Supporting Information). The fungal was kept on potato dextrose agar slant (PDA) at 4 °C and stored at Chengdu Institute of Biology fungus storage center (No. CIB-G3604). Fermentation, Extraction, and Isolation. The fungal seed culture and fermentation process were identical to those reported.16 The fermented solid rice medium (5 kg) was soaked with ethyl acetate (10 L × 2, 2 day for each time) at room temperature. The ethyl acetate was evaporated under reduced pressure to afford a residue (35.0 g). This residue was divided into four fractions (Fra. A, B, C and D) over silica gel column (200 g, 300−400 mesh, Φ 45 cm × 5.5 cm), eluted with petroleum ether−acetone (6:1, 3:1, 1.5:1, 0:1, successively). Fraction A contained oil and ergosterol. Fraction B was separated over Sephadex LH-20 column eluted with CHCl3−MeOH (1:1, v/v) to obtain compounds 8 (10 mg) and 10 (110 mg). Fraction C was further subjected to silica gel column chromatography (80 g, 300−400 mesh, Φ 2.5 cm × 45 cm, P.E.−acetone, 4:1, 2000 mL) to afford Subfra.C2. Compound 9 (292 mg) was obtained from C2 by Sephadex LH-20 column (CHCl3−MeOH, 1:1). Compound 2 (1.2 g) was crystallized from acetone solution of Fraction D. The mother liquid of compound 2 afforded compound 1 (9 mg) and Subfra.D0 through semipreparative high-performance liquid chromatography with mobile phase MeOH with H2O mixture (83:17) as solvents (flow rate: 2.5 mL/min, UV detector was set at 254 nm). Compound 3 (23 mg) was obtained by semipreparative high-performance liquid chromatography eluted with a

CH3CN with H2O mixture (68:32, v/v) from Subfra.D0 (flow rate: 2.5 mL/min, UV detector was set at 254 nm). Chaetocochin J (1): white powder; [α]20D + 199° (c 0.1, acetone); UV (CH3OH) λmax (log ε) 207 (4.11), 220 (4.25), 292 (3.56) nm; IR (KBr) νmax 3433, 2929, 1676, 1645, 1455, 1206, 1064, and 745 cm−1; 1H and 13C NMR see Table 1; HR-ESIMS m/z 733.1022 [M + Na]+ (calcd for C31H30N6O6S4Na, 733.1002). Chaetoglobinol A (8): yellow powder; [α]20D +7° (c 0.1, acetone); UV (CHCl3) λmax nm (log ε) 239 (4.27), 411.3 (3.99) nm; IR (KBr) νmax 3400, 2922, 1672, 1615, 1511, 1474, 1422, 1399, 1311, 1238, 1135, 1071, 803, 777, and 615 cm−1; 1H and 13C NMR, see Table 2; HRESIMS m/z 521.2073 [M − H]− (calcd for C32H29N2O5, 521.2082). UPLC−MS Analysis. Fraction D was analyzed on a Waters ACQUITY UPLC−MS system (Waters Corp., Milford, MA) with an ACQUITY UPLC BEH-C18 column (2.1 × 100 mm, 1.7 μm) and detected with UV detector at 254 nm. The mobile phase was a mixture of methanol and water (38:62, v/v). The total running time for this analysis was 7.0 min. Mass detection of products was carried out on a Waters TQ mass spectrometer. The capillary voltage was set at 3 and 5 kV for the positive and negative ESI modes, respectively. Nitrogen was used as the nebulizing gas, and the source temperature was set at 150 °C. The scan range was m/z 130−1000. Data processing was performed automatically with MassLynx workstation. Antimicrobial Assay. The antibacterial activity was evaluated according to the reported procedure with little modification.40,41 Activity was determined using the Oxford cup method with medium (dextrose 20.0 g/L, beef infusion 10 g/L, NaCl 5 g/L, agar 17 g/L) respectively, inoculated with strains of E. coli 1.044 and B. subtilis 1.079. To each cup was added 200 μL of sample (compounds 1−3, 8) dissolved in DMSO. Methicillin (5 μg/mL) and DMSO were used as positive and negative controls, respectively. The plates were incubated at 37 °C for 24 h. The antimicrobial activity was evaluated by measuring the diameter zone of growth inhibition against the test microorganism. MIC was detected complying with the method described by Kubo et al.42 All the test samples were dissolved in DMSO and the final concentration of DMSO was not over 5% (v/v). The final range of test sample dilutions was between 50 and 0.19 μg/mL in the MHB broth. The final bacteria concentration in each dilution was 1 × 108 CFU/mL. The tubes were incubated at 37 °C for 24 h and then examined for evidence of the growth. MIC was determined as the lowest F

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concentration of the antibacterial agents to inhibit bacterial growth. The antifungal activity was assayed by the Oxford cup method with medium [potato extract 20% (potato:water, w/v; boiling 20 min), dextrose 20.0 g/L, agar 17 g/L] inoculated with strains of C. albicans, F. graminearum, F. vasinfectum, S. cerevisiae, and A. niger. The plates were incubated at 31 °C for 72 h. Antioxidative Assay. The antioxidative activity was evaluated by testing the DPPH free radical scavenging, ABTS cation radical scavenging, and superoxide anion radical scavenging capacities of the compounds.43

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ASSOCIATED CONTENT

S Supporting Information *

1D and 2D NMR spectra of compounds 1 and 8, and the DNA sequence of C. globosum. The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/ np5007235.

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AUTHOR INFORMATION

Corresponding Author

*Tel: +86-28-82890829. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We are very grateful to Miss Dong-Mei Fang for detecting the NMR data, and professor Ying-Gang Luo team for testing the DNA sequence of C. globosum. This study was financially supported by the National Natural Science Foundation of China (No. 21272228), the Applied and Basic Research Program of Sichuan Province (2013JY0049), and the National New Drug Innovation Major Project of China (2011ZX09307-002-02).

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DOI: 10.1021/np5007235 J. Nat. Prod. XXXX, XXX, XXX−XXX