Abstract
Five novel tigliane-type diterpenes, stelleracins A–E (3–7), a novel flavanone dimer, chamaeflavone A (8), and six known compounds were isolated from roots of Stellera chamaejasme. Their structures were elucidated by extensive spectroscopic analyses. The isolated compounds were evaluated for anti-HIV activity in MT4 cells. New compounds 3–5 showed potent anti-HIV activity (EC90 0.00056–0.0068 μM) and relatively low or no cytotoxicity (IC50 4.4–17.2 μM). These new compounds represent promising new leads for development into anti-AIDS clinical trial candidates.
Stellera chamaejasme L. (Thymelaeaceae) is a toxic perennial plant that grows at high altitudes in China and Nepal. Its roots have been used in Traditional Chinese Medicine as an emulgent, anthelmintic, and dermatological agent. During our ongoing chemical investigations of Nepalese medicinal plants, a MeOH extract of S. chamaejasme showed potent anti-HIV activity. Investigation of the chemical constituents of this extract resulted in the isolation of eight daphnane-type diterpenes.1 Two of these compounds, stelleralide A and gnidimacrin, showed extremely potent anti-HIV activity (EC90 0.40 nM) with relatively low cytotoxicity (IC50 4.3 μM) in MT4 cells.1 Herein, we report a further phytochemical investigation of S. chamaejasme, including the isolation and structural determination of five novel tigliane-type diterpenes (3–7), a novel flavanone dimer (8), and six known compounds; stellerarin (1)2, 12-O-benzoylphorbol 13-octanoate (2),3 (−)-chamaejasmenin B (9),4,5 (+)-chamaejasmenin C (10),4,5 1,5-diphenyl-2(E)-penten-1-one (11),6,7 and 1-(ω-feruloyldocosanoyl)glycerol (12).8 The anti-HIV activity of compounds 1–12 was also evaluated in our study.
RESULTS AND DISCUSSION
A MeOH extract from roots of S. chamaejasme collected in Nepal was partitioned between EtOAc and H2O. The EtOAc fraction was fractionated by ODS and silica gel column chromatography, as well as preparative HPLC, to afford seven tigliane-type diterpenes (1–7), three flavanone dimers (8–10), and two phenolic compounds (11 and 12).
New compounds 3–7 were obtained as white powders, and their 1H and 13C NMR spectra showed characteristic resonances for the gem-dimethyl cyclopropane moiety of tigliane-type diterpenes (Table 1). A comparison of the NMR data of stelleracin A (3), and stelleracin B (4) with those of the known compounds 1 and 2 indicated that the four compounds had the same structures, except for the 13-acyl moiety.
Table 1.
1H and 13C NMR Spectroscopic Data (δ, CDCl3) for 3–7
| position | 3 | 4 | 5 | 6 | 7 | |||||
|---|---|---|---|---|---|---|---|---|---|---|
|
| ||||||||||
| δC, type | δH (J in Hz) | δC, type | δH (J in Hz) | δC, type | δH (J in Hz) | δC, type | δH (J in Hz) | δC, type | δH (J in Hz) | |
| 1 | 160.8, CH | 7.6, dq (2.5,1.5) | 160.7, CH | 7.61, dq (2.5,1.5) | 161.9, CH | 7.68, dq (2.5,1.5) | 160.3, CH | 7.66, dq (2.5,1.5) | 160.2, CH | 7.66, dq (3.0,1.5) |
| 2 | 132.9, C | 132.9, C | 134.1, C | 134.1, C | 134.1, C | |||||
| 3 | 209.0, C | 208.9, C | 209.6, C | 206.2, C | 206.2, C | |||||
| 4 | 73.7, C | 73.7, C | 73.4, C | 72.5, C | 72.5, C | |||||
| 5 | 38.6, CH | 2.50, d (19.5) | 38.6, CH | 2.50, d (19.0) | 71.7, CH | 4.38, s | 133.7, CH | 6.42, d (2.0) | 133.8, CH | 6.42, d (2.0) |
| 2.60, d (19.5) | 2.60, d (19.0) | |||||||||
| 6 | 140.5, C | 140.5, C | 140.2, C | 150.6, C | 150.6, C | |||||
| 7 | 129.2, CH | 5.72, d (5.0) | 129.2, CH | 5.72, br.d (5.5) | 132.8, CH | 5.73, d (5.5) | 83.1, CH | 4.81, dd (9.0,2.0) | 83.1, CH | 4.80, dd (9.0,2.0) |
| 8 | 39.1, CH | 3.34, dd (5.0,5.0) | 39.1, CH | 3.32, dd (5.5,5.5) | 38.9, CH | 3.54, dd (5.5,5.5) | 46.0, CH | 2.94, dd (9.0,5.5) | 46.0, CH | 2.93, dd (9.0,5.5) |
| 9 | 78.3, C | 78.3, C | 77.3, C | 75.0, C | 74.9, C | |||||
| 10 | 56.2, CH | 3.29, dd (2.5,2.5) | 56.2, CH | 3.29, dd (2.5,2.5) | 53.8, CH | 3.06, dd (2.5,2.5) | 57.3, CH | 3.02, dd (2.5,2.5) | 57.3, CH | 3.02, dd (3.0,3.0) |
| 11 | 43.3, CH | 3.32, dq (10.0,6.5) | 43.3, CH | 2.32, m | 44.1, CH | 2.24, dq (10.0,6.5) | 44.7, CH | 2.35, dq (10.0,6.5) | 44.7, CH | 2.36, dq (10.0,6.5) |
| 12 | 77.6, CH | 5.67, d (10.0) | 77.6, CH | 5.66, d (10.0) | 77.6, CH | 5.64, d (10.0) | 77.7, CH | 5.71, d (10.0) | 77.7, CH | 5.72, d (10.0) |
| 13 | 65.6, C | 65.7, C | 65.4, C | 65.8, C | 65.8, C | |||||
| 14 | 36.6, CH | 1.14, d (5.0) | 36.6, CH | 1.14, d (5.5) | 36.7, CH | 1.12, d (5.5) | 31.8, CH | 1.70, d (5.5) | 31.8, CH | 1.70, d (5.5) |
| 15 | 26.0, C | 26.0, C | 26.2, C | 26.1, C | 26.1, C | |||||
| 16 | 23.8, CH3 | 1.21, s | 23.8, CH3 | 1.21, s | 23.7, CH3 | 1.20, s | 23.8, CH3 | 1.28, s | 23.8, CH3 | 1.28, s |
| 17 | 17.0, CH3 | 1.38, s | 17.0, CH3 | 1.38, s | 17.0, CH3 | 1.35, s | 16.8, CH3 | 1.36, s | 16.8, CH3 | 1.36, s |
| 18 | 14.5, CH3 | 0.95, d (6.5) | 14.5, CH3 | 0.95, d (7.5) | 15.0, CH3 | 0.98, d (6.5) | 14.8, CH3 | 0.97, d (6.5) | 14.8, CH3 | 0.98, d (6.5) |
| 19 | 10.1, CH3 | 1.77, dd (2.5,1.5) | 10.1, CH3 | 1.77, dd (2.5,1.5) | 10.0, CH3 | 1.78, dd (2.5,1.5) | 10.2, CH3 | 1.80, dd (2.5,1.5) | 10.2, CH3 | 1.80, dd (3.0,1.5) |
| 20 | 68.1, CH3 | 4.01, d (13.0) | 68.0, CH3 | 4.01, d (13.0) | 67.8, CH2 | 4.23, s | 66.5, CH3 | 4.25, d (11.0) | 66.6, CH3 | 4.25, d (11.0) |
| 4.07, d (13.0) | 4.07, d (13.0) | 4.48, d (11.0) | 4.49 d (11.0) | |||||||
| 1′ | 176.0, C | 175.9, C | 176.7, C | 176.9, C | 176.8, C | |||||
| 2′ | 34.5, CH2 | 2.45, m | 34.3, CH2 | 2.44, dd (7.5,7.5) | 34.4, CH2 | 2.33, ddd (15.0,7.5,7.5) | 34.4, CH2 | 2.34, ddd (16.0,8.0,8.0) | 34.4, CH2 | 2.34, ddd (16.0,8.0,8.0) |
| 2.40, ddd (15.0,7.5,7.5) | 2.40, ddd (16.0,8.0,8.0) | 2.40, ddd (16.0,8.0,8.0) | ||||||||
| 3′ | 22.4, CH2 | 2.38, m | 22.4, CH2 | 2.43, dd (7.5,1.5) | 24.5, CH2 | 1.64, ddd (15.0,7.5,7.5) | 24.6, CH2 | 1.65, ddd (16.0,8.0,8.0) | 24.6, CH2 | 1.65, ddd (16.0,8.0,8.0) |
| 4′ | 127.0, CH | 5.33, dtt (10.5,7.0,1.5) | 127.3,a CH | c | 28.9,a CH2 | b | 29.1,a CH2 | b | 28.9,a CH2 | b |
| 5′ | 131.8, CH | 5.42, dt (10.5,7.0) | 129.9,a CH | c | 29.0,a CH2 | b | 29.2,a CH2 | b | 29.0,a CH2 | b |
| 6′ | 27.2, CH2 | 2.03, dt (7.0,7.0) | 25.5, CH2 | 2.80, dd (7.5,7.5) | 31.6,a CH2 | b | 29.3,a CH2 | b | 31.6, CH2 | b |
| 7′ | 29.2, CH2 | b | 126.8, CH | 5.29, dt (11.0,7.5) | 22.6,a CH2 | b | 29.4,a CH2 | b | 22.6, CH2 | b |
| 8′ | 31.5, CH2 | b | 132.1,a CH | c | 14.0, CH3 | 0.88, t (6.5) | 31.8, CH3 | b | 14.1, CH2 | 0.88, t (7.0) |
| 9′ | 22.5, CH2 | b | 20.5, CH2 | 2.06, dq (7.5,7.5) | 22.7, CH2 | b | ||||
| 10′ | 14.0, CH2 | 0.88, t (7.0) | 14.2, CH3 | 0.96, t (7.5) | 0.88, d (6.5) | 14.1, CH3 | 0.88, t (7.0) | |||
| 1″ | 166.2, C | 166.3, C | 166.2, C | 166.3, C | 166.3, C | |||||
| 2″ | 130.1, C | 130.1, C | 130.0, C | 130.2, C | 130.2, C | |||||
| 3″, 7″ | 129.7, CH | 8.03, dd (7.5,1.5) | 129.7, CH | 8.03, dd (7.5,1.5) | 129.7, CH | 8.02, dd (7.5,1.5) | 129.7, CH | 8.03, dd (7.5,1.5) | 129.8, CH | 8.04, dd (7.5,1.5) |
| 4″, 6″ | 128.4, CH | 7.45, dd (7.5,7.5) | 128.4, CH | 7.45, dd (7.5,7.5) | 128.5, CH | 7.45, dd (7.5,7.5) | 128.4, CH | 7.45, dd (7.5,7.5) | 128.4, CH | 7.45, dd (7.5,7.5) |
| 5″ | 133.0, CH | 7.58, tt (7.5,1.5) | 133.0, CH | 7.58, tt (7.5,1.5) | 133.1, CH | 7.58, tt (7.5,1.5) | 133.0, CH | 7.57, tt (7.5, 1.5) | 133.0, CH | 7.58, tt (7.5,1.5) |
These resonances in the same column are interchangeable,
1.21~1.38 (m),
5.34~5.44 (3H, m)
The molecular formula of 3 was determined as C37H48O8 by HR-FAB-MS. Thus, compound 3 has two fewer hydrogen atoms than 1, suggesting the presence of a decenoate moiety in 3. The olefinic position in this moiety was established at C-4′, based on HMBC correlations from δH 2.45 (H2-2′) and 2.38 (H2-3′) to δC 176.0 (C-1′), as well as 1H -1H COSY correlations between δH 2.38 (H2-3′) and 5.33 (H-4′). The coupling constant between the olefinic protons was 10.5 Hz, indicating a cis relationship, and accordingly, the 13-acyl moiety in 3 was assigned as 4Z-decenoate.
The molecular formula of 4 (C37H46O8 from HR-FAB-MS) contained two fewer hydrogen atoms than that of 3, indicative of a decadienoate 13-acyl moiety. The 1H NMR spectrum included resonances at δH 5.29 (1H, dt, J = 11.0, 7.5 Hz) and 5.34–5.44 (3H, m) for four olefinic protons, which had 1H-1H COSY correlations with H2-9′, H2-6′ and H2-3′. Based on these data, the two double bonds were assigned at C-4′ and C-7′. The orientations of both olefins were established as cis, based on the chemical shifts of C-3′, C-6′ and C-9′ (δC 22.4, 25.5 and 20.5, respectively). Thus, the 13-acyl moiety in 4 was fully determined as 4Z,7Z-decadienoate.
The molecular formula of stelleracin C (5) was determined as C35H46O9 from HR-FAB-MS. Thus, compound 5 contains one more oxygen atom than 2, which is consistent with the presence of an additional hydroxy group in 3. Accordingly, the C-5 methylene resonances at δH 2.50, 2.60 and δC 38.9 in the 1H and 13C NMR spectra of 2 were replaced by hydroxymethylene resonances at δH 4.38 and δC 71.7 in 5. A hydroxy moiety at C-5 was further confirmed by HMBC correlations from δH 5.73 (H-7) and 3.06 (H-10) to δC 71.7 (C-5). The β-orientation of this hydroxy moiety was deduced from a ROESY correlation between δH 3.06 (H-10) and 4.38 (H-5).
The molecular formula of stelleracin D (6) was determined by HR-FAB-MS as C37H50O10, and contains two more oxygen atoms than that of 1. A comparison of the 1H and 13C NMR spectroscopic data of 6 and 1 revealed large differences in the B-ring resonances. From detailed analyses of 2D NMR spectroscopic data, the olefinic proton resonance at δH 6.42 in 6 was assigned to H-5 based on HMBC correlations with δC 206.2 (C-3), 57.3 (C-10) and 66.5 (C-20). Thus, 6 contains a Δ5,6 olefin moiety. In addition, the oxymethine proton resonance at δH 4.81 in 6 was assigned to C-7, based on sequential 1H-1H COSY correlations between δH 1.70 (H-14), 2.94 (H-8) and 4.81 (H-7), and HMBC correlations from H-7 to δC 75.0 (C-9), 31.8 (C-14) and 66.5 (C-20). Based on the molecular formula and the chemical shift of the C-7 resonance at δC 83.1, the presence of a hydroperoxy moiety at C-7 was determined. The β-orientation of this moiety was established from ROESY correlations between H-7/H-10 and H-7/H-14.
Stelleracin E (7) and 6 had superimposable 1H and 13C resonances, except for those of the C-13 acyl moiety. The acyl group in 7 was established as octanoate, based on the molecular formula of C35H46O10 and the integrated values of the relevant 1H and 13C NMR resonances.
Chamaeflavone A (8) was isolated as a white powder, [α]D22 −319.0 (c 0.11, MeOH). Its molecular formula was determined as C32H26O10 by positive-ion HRFABMS, and was the same as that of (−)-chamaejasmenin B (9). Compound 8, 9, and 10 had similar 1H and 13C resonance patterns, suggesting that 8 is also a 3,3″ biflavanone. Based on ROESY correlations between 7-OCH3/H-6, H-8, and 4′-OCH3/H-3′, H-5′, two methoxy moieties were present in the same flavanone monomer at C-7 and C-4′. Two fragment peaks at m/z 299 and 271 in the FABMS spectrum also supported this conclusion. The trans relationships of both H-2/H-3 and H-2″ H-3″ were determined from their coupling constant values (12.0 Hz) by 1H NMR decoupling experiments, and contrasted with the cis relationships of the same hydrogens in 9 and 10 (coupling constant values of 0 Hz). In the CD spectrum, a negative Cotton effect at 311 nm and positive Cotton effect at 287 nm were consistent with 2R and 2″ R configurations.
The newly isolated compounds (1–12) were evaluated for anti-HIV-1 activity against NL4-3 virus in MT4 lymphocytes. The anti-HIV EC90 values, defined as the compound concentration that inhibited HIV-1 replication by 90%, are summarized in Table 3. Diterpenes 1, 2, and 3 were the most potent compounds, with comparable anti-HIV EC90 values of 0.50, 0.56, and 0.66 nM, respectively. All three compounds also demonstrated relatively low cytotoxicity (IC50 4.4–5.1 μM). Structurally, these three compounds differ only in the C-13 ester substituent (decanoate in 1, octanoate in 2, and 4Z-decenoate in 3). Compounds 4 and 5 showed lower, but still significant, anti-HIV potency with EC90 values of 6.8 and 3.8 nM, respectively. Compound 5 has a β-hydroxy group at C-5, while the more potent 1, 2, and 3 are unsubstituted at this position. Compound 4 showed lower anti-HIV potency, and has a 4Z,7Z-decadienoate ester rather than the less rigid ester side chains in 1, 2, and 3. Compounds 6 and 7 with a C-7 hydroperoxy moiety and a Δ5,6 rather than Δ6,7 olefin (as in compounds 1–5) showed significantly decreased anti-HIV activity with EC90 values of 0.49 and 1.52 μM, respectively. From the preliminary SAR, we can conclude that, in addition to the C-13 ester substituent, the B-ring also plays a critical role in the anti-HIV activity of tigliane-type diterpenes. Finally, the new flavanone dimer 8 and known phenolic compound 12 showed marginal anti-HIV activity with EC90 values of 4.21 and 3.63 μM, respectively.
Table 3.
Anti-HIV Data of 1–12a
| compound | anti-HIV (NL4-3) EC90 (μM) | cytotoxicity (MT-4) IC50 (μM) |
|---|---|---|
| 1 | 0.00050 | 5.1 |
| 2 | 0.00056 | 4.4 |
| 3 | 0.00066 | 4.7 |
| 4 | 0.0068 | 7.8 |
| 5 | 0.0038 | 17.2 |
| 6 | 0.49 | 3.5 |
| 7 | 1.52 | 15.8 |
| 8 | 4.21 | 17.5 |
| 12 | 3.63 | 16.2 |
Compounds 9–11 were inactive.
In conclusion, seven tigliane-type diterpenes (1–7), three flavanone dimers (8–10), and two phenolic compounds (11 and 12) were isolated from roots of Stellera chamaejasme L. Six compounds, stelleracins A–E (3–7) and chamaeflavone A (8), were identified for the first time. Three compounds (1, 2, and 3) exhibited potent anti-HIV EC90 values of less than 1 nM. The relevant structural pharmacophores were the ester side chain at C-13 and the substitution/unsaturation pattern at C-5 to C-7.
The tigliane-type diterpenes described in this study share some structural similarity to prostratin (12-deoxyphorbol-13-acetate) and DPP (12-deoxyphorbol-13-phenylacetate), as well as our previously discovered daphnane-type diterpenes,1 stelleralide A and gnidimacrin. The anti-HIV-1 activity of prostratin, DPP, and gnidimacrin is due, at least in part, to an ability to activate protein kinase C and down-regulate HIV-1 cellular receptors, CD4 and chemokine receptors, such as coreceptor CCR5.9–12 Due to their structural similarity, the new compounds’ extremely potent anti-R5 HIV-1 activity likely results from the same mechanisms. Although gnidimacrin is a potent inhibitor of many HIV-1 R5 viruses, it was essentially inactive against X4 or dual tropic HIV-1 replication in peripheral blood mononuclear cells (PBMCs).12 Therefore, it is likely that these new compounds will also be inactive under the same conditions.
EXPERIMENTAL SECTION
General Experimental Procedures
The UV spectra were obtained with a Hitachi U-2800 spectrophotometer, and the IR spectra were measured with a Hitachi DFT/IR 460 (KBr disk) spectrometer. Optical rotations were measured with a Hitachi DIP-1000 polarimeter in a 0.5 dm cell. The 1H and 13C NMR measurements were recorded using a Varian XL-400 NMR spectrometer with TMS as the internal reference, and chemical shifts are expressed in δ (ppm). FABMS and HRFABMS were conducted using JEOL JMS-AX505 HA and JMS-700 M Station mass spectrometers. Silica gel (Kanto Chemical Corporation) and ODS (Senshu Scientific Co., Ltd.) were used for column chromatography. For HPLC, a Waters 515 HPLC system, equipped with Shodex RI-72 refractive index and Shimadzu SPD-10AV UV detectors, was used. TLC was carried out on Kieselgel 60 F254 Art.5715 (E. Merck) and RP-18 F254 Art.15389 (E. Merck).
Plant Material
The roots of S. chamaejasme were collected from Chele (Alt. 3115m) to Shyammochem (Alt. 3755m), upper Mustang, Mustang District, Nepal in July 2002, and identified by Dr. Takahide Kurosawa (Faculty of Symbiotic System Science, Fukushima University). A plant specimen [LOM-SP020729(047)] is deposited in the herbarium of the University of Tokyo.
Extraction and isolation
Roots of S. chamaejasme (4.2 kg) were extracted with MeOH. The methanolic extract was concentrated (840.2 g), suspended in H2O, and then partitioned successively with EtOAc. The EtOAc layer was evaporated under reduced pressure below 40 °C to give a residue (471.6 g), which was passed over an ODS column, and washed with a gradient of MeOH-H2O to give eight fractions (1–8). Fractions 2 and 3 were purified by repeated RP-HPLC to give 8 (15.6 mg), 9 (27.7 mg), 10 (348.4 mg), 11 (88.6 mg), and 12 (1.9 mg). Fraction 4 was purified by repeated RP-HPLC to give 1 (48.6 mg), 2 (114.3 mg), 3 (27.4 mg), 4 (5.6 mg), 5 (7.4 mg), 6 (2.2 mg), and 7 (2.0 mg).
Stelleracin A (3)
white powder; [α]D23 +2.5 (c 0.13, MeOH); UV (MeOH) λmax (log ε) 230 (4.31) nm; CD (c 2.19 × 10−5, MeOH) Δε24 +0.77 (307), 0 (285), −4.8 (258), 0 (241), +24.1 (225); IR (KBr) νmax 3413, 2925, 1720, 1711, 1629 cm−1; 1H NMR (CDCl3, 400 MHz) and 13C NMR (CDCl3, 100 MHz), see Table 1; positive-ion FABMS m/z 621 [M + H]+, 643 [M + Na]+; positive-ion m/z HRFABMS 643.3270 [M+Na]+(calcd for C37H48O8Na, 643.3242).
Stelleracin B (4)
white powder; [α]D23 +2.3 (c 0.14, MeOH); UV (MeOH) λmax (log ε) 230 (4.33) nm; CD (c 2.26 × 10−5, MeOH) Δε24 (nm) +1.4 (301), 0 (282), −4.2 (258), 0 (242), +23.9 (225); IR (KBr) νmax 3414, 2925, 1717, 1710, 1629 cm−1; 1H NMR (CDCl3, 400 MHz) and 13C NMR (CDCl3, 100 MHz), see Table 1; positive-ion FABMS m/z 641 [M + Na]+; positive-ion HRFABMS m/z 641.3088 [M + Na]+(calcd for C37H46O8Na, 641.3086).
Stelleracin C (5)
white powder; [α]D23 −37 (c 0.12, MeOH); UV (MeOH) λmax (log ε) 230 (4.31) nm; CD (c 1.96 × 10−5, MeOH) Δε24 (nm) +1.2 (302), 0 (280), −9.1 (251), 0 (240), +24.9 (225); IR (KBr) νmax 3404, 2926, 1721, 1712, 1627, 1603 cm−1; 1H NMR (CDCl3, 400 MHz) and 13C NMR (CDCl3, 100 MHz), see Table 1; positive-ion FABMS m/z 633 [M + Na]+; positive-ion HRFABMS m/z 633.3055 [M + Na]+ (calcd for C35H46O9Na, 633.3034).
Stelleracin D (6)
white powder, [α]D23 −6.9 (c 0.13, MeOH); UV (MeOH) λmax (log ε) 230 (4.33) nm; CD (c 1.99×10−5, MeOH) Δε24 (nm) −25.5 (243), 0 (230), +22.6 (207); IR (KBr) νmax 3388, 2925, 1719, 1628, 1603 cm−1; 1H NMR (CDCl3, 400 MHz) and 13C NMR (CDCl3, 100 MHz), see Table 1; positive-ion FABMS m/z 677 [M + Na]+; negative-ion FABMS m/z 653[M −H]−; positive-ion HRFABMS m/z 677.3292 [M + Na]+(calcd for C37H50O10Na, 677.3297).
Stelleracin E (7)
white powder, [α]D22 −38 (c 0.12, MeOH); UV (MeOH) λmax (log ε) 230 (4.26) nm; CD (c 1.91×10−5, MeOH) Δε24 (nm) −15.0 (243), 0 (230), +13.7 (207); IR (KBr) νmax 3390, 2926, 1719, 1626, 1603 cm−1; 1H NMR (CDCl3, 400 MHz) and 13C NMR (CDCl3, 100 MHz), see Table 1; positive-ion FABMS m/z 649 [M + Na]+; negative-ion FABMS m/z 625 [M−H]−; positive-ion HRFABMS m/z 649.2979 [M + Na]+ (calcd for C35H46O10Na, 649.2984).
Chamaeflavone A (8)
white powder; [α]D22 −319 (c 0.11, MeOH); UV (MeOH) λmax (log ε) 297 (4.25) nm; CD (c 1.93×10−5, MeOH) Δε24 (nm) −25.4 (311), 0 (299), +32.3 (288), 0 (263), −4.6 (255), 0 (242), −35.4 (218); IR (KBr) νmax 3431, 1638, 1611, 1517, 1459 cm−1; 1H NMR (CDCl3, 400 MHz) and 13C NMR (CDCl3, 100 MHz), see Table 2; positive-ion FABMS m/z 571 [M + H]+, 593 [M + Na]+, 299 [M - C15H11O5]+, 271 [M-C17H15O5]+; positive-ion HRFABMS m/z 593.1448 [M + Na]+(calcd for C32H26O10Na, 593.1418).
Table 2.
1H and 13C NMR Spectroscopic Data (δ, CDCl3) for 8
| position | δC | δH (J in Hz) |
|---|---|---|
| 2 | 83.4 | 5.93, d (12.0)a |
| 3 | 49.7 | 2.82, dd (12.0,1.5) |
| 4 | 196.5 | |
| 5 | 164.3 | |
| 6 | 94.1 | 5.95, d (2.0) |
| 7 | 167.9 | |
| 8 | 95.2 | 6.06, d (2.0) |
| 9 | 162.6b | |
| 10 | 103.2c | |
| 1′ | 128.5 | |
| 2′,6′ | 129.2 | 7.04, d (8.0) |
| 3′,5′ | 114.3 | 6.87, d (8.0) |
| 4′ | 160.4 | |
| 7-OCH3 | 55.7 | 3.77, s |
| 4′-OCH3 | 55.4 | 3.85, s |
| 2″ | 83.4 | 5.92, d (12.0)a |
| 3″ | 49.7 | 2.80 dd (12.0,1.5) |
| 4″ | ||
| 5″ | ||
| 6″ | 96.7 | 5.98, d (2.0) |
| 7″ | 164.1 | |
| 8″ | 95.3 | 5.86, d (2.0) |
| 9″ | 162.9b | |
| 10″ | 103.1c | |
| 1‴ | 128.7 | |
| 2‴,6‴ | 129.4 | 6.98, d (8.0) |
| 3‴,5‴ | 115.7 | 6.80, d (8.0) |
| 4‴ | 156.5 | |
| 5,5″-OH | 11.89, d (14.5) |
Interchangeable signals
Anti-HIV Assay
MT4 cells were infected with HIV-1 NL4-3 (multiplicity of infection = 0.001) in the presence of various concentrations of compounds. Fresh medium, which contained appropriate concentrations of the compounds, was added to the culture 48 h after infection to maintain normal cell growth. Virus replication was analyzed on day-4 post-infection using p24 ELISA kits from Perkin-Elmer. The compound concentration that inhibited HIV-1 replication by 90% (EC90) was calculated by using the biostatistic software Calcusun (Biosoft).
Cytotoxicity Study
Cytotoxicity of the purified compounds toward MT4 cells was determined by using a cell viability kit provided by Promega. The CellTiter-Glo Luminescent Cell Viability Assay is a simple method of determining the viability of the cells in culture based on quantitation of ATP in metabolically active cells. The CellTiter-Glo reagent was added to MT4 cells that were cultured parallel to the antiviral assays. The compound concentration that decreased the cell viability by 50% (IC50) was calculated by using Calcusun (Biosoft).
Supplementary Material
Acknowledgments
This investigation was supported by NIH Grant AI-033066 from the National Institute of Allergy and Infectious Diseases (NIAID) awarded to K.H.L. This study was also supported in part by the Department of Health Clinical Trial and Research Center of Excellence (DOH100-TD-B-111-004).
Footnotes
ASSOCIATED CONTENT
Extraction procedures from Stellera chamaejasme, HPLC conditions for separation of compounds 1–10, 1H-NMR, 13C-NMR COSY, HMBC, NOESY and ROESY data and spectra for 1–10. Comparison of key HMBC/COSY (Fig. 1) and ROESY (Fig. 2) correlations in 5 and 6. This material is available free of charge via the Internet at http://pubs.acs.org.
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