Meroterpenoids and Chalcone-Lignoids from the Roots of Mimosa

Oct 7, 2016 - of Mimosa diplotricha. Diplomeroterpenoids A−F consist of a 4H- chromen-4-one and a diterpenoid unit, and their absolute configuration...
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Meroterpenoids and Chalcone-Lignoids from the Roots of Mimosa diplotricha Chun-Tang Chiou,† Chien-Chang Shen,† Tung-Hu Tsai,‡ Yu-Jen Chen,§ and Lie-Chwen Lin*,†,⊥ †

National Research Institute of Chinese Medicine, Ministry of Health and Welfare, Taipei, Taiwan Institute of Traditional Medicine, National Yang-Ming University, Taipei, Taiwan § Department of Radiation Oncology, Center of Biomedical Development, and Laboratory of Cancer Therapeutics, MacKay Memorial Hospital, Taipei, Taiwan ⊥ Graduate Institute of Integrated Medicine, China Medical University, Taichung, Taiwan ‡

S Supporting Information *

ABSTRACT: Six new meroterpenoids, diplomeroterpenoids A− F (1−6), two new chalcone-lignoids, diplochalcolins A and B (7, 8), and 13 known compounds were isolated from the root extract of Mimosa diplotricha. Diplomeroterpenoids A−F consist of a 4Hchromen-4-one and a diterpenoid unit, and their absolute configurations were determined by X-ray crystallographic analysis. Compounds 1−3 and 5 showed potent inhibitory activity on protein farnesyl transferase, with IC50 values from 5.0 to 8.5 μM. Compound 1 showed antiproliferative activity against human hepatoblastoma HepG2 cells with a GI50 value of approximately 8.6 μM. retinitis pigmentosa, and premature aging syndromes. 4 Currently, PFTase inhibitors are being developed in attempts to treat cancer, progeria, and parasite infections,5 as well as neurodegenerative diseases.6 Herein, the isolation of six new meroterpenoids (1−6), two new chalcone-lignoids (7, 8), and 13 other components (9−21) from the root of M. diplotricha is described. The PFTase inhibitory activity and cytotoxicity against tumor cell lines of compounds 1−6 are also reported.

Mimosa diplotricha C. Wright ex Sauvalle (synonym: Mimosa invisa, Fabaceae), an erect shrub and a scrambling climber, is widely distributed in the open wastelands of central and southern Taiwan.1 The roots and the whole plant of M. diplotricha are used in Formosan folk medicine as an analgesic, anticancer remedy, antidote, hemostatic agent, and tranquilizer.2 Our previous investigation of this plant led to the isolation of flavonoids and triterpenoids from the aerial parts and showed that diplotrin B and 5″-methoxyhydnocarpin-D had antiproliferative activities against cancer cell lines.3 The EtOH extract of the roots of M. diplotricha also showed cytotoxic activity against various human tumor cell lines. A comparison of the HPLC profiles of the extracts of the roots and the aerial parts displayed different peak patterns in some segments (Figure S56, Supporting Information), which implied that some other bioactive constituents could exist in the roots of M. diplotricha. Therefore, a chemical constituent study on the root extract of M. diplotricha was conducted. Protein farnesyl transferase (PFTase) catalyzes a covalent linkage of a farnesyl group to the cysteine residue at the CAAX motif (C = cysteine, A = aliphatic amino acid, X = any amino acid) near the C-terminus of proteins. This post-translational modification, as a result, increases the hydrophobicity of the target proteins and allows them to interact with membrane and partner proteins with the correct cellular localization so that they can perform their functions normally. The substrates of PFTase include small GTPases, tyrosine phosphatases, the nuclear lamina, cochaperones, and centromere-associated proteins. The dysregulation of PFTase is associated with various diseases, such as cancer, neurodegenerative disorders, © 2016 American Chemical Society and American Society of Pharmacognosy

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RESULTS AND DISCUSSION Chromatography of the CHCl3 extract from the roots of M. diplotricha on silica gel, Sephadex LH-20, and C18 columns with various solvent systems afforded six new meroterpenoids (1−6), two new chalcone-lignoids (7, 8), and the 13 known compounds, hydnocarpin (9),7 7,4′-dihydroxyflavone (10),8 chrysoeriol (11),9 apigenin (12),9 diplotrin B (13),3 2′hydroxy-3,7,4′,5′-pentamethoxyflavone (14),3 hernancorizin (15), 3 diplotasin (16), 3 7-hydroxy-8-methoxychromone (17),10 (+)-syringaresinol (18),11 4-hydroxy-3,5-dimethoxybenzoic acid (19),12 β-sitosterol (20),13 and β-sitosterol glucoside (21).14 The spectroscopic and spectrometric data of the known compounds were in agreement with the literature values. Diplomeroterpenoid A (1) has the molecular formula C37H42O9 according to HRESIMS analysis (m/z 631.2914 [M + H]+, calcd for C37H43O9, 631.2907) and an [α]26D value of −173. The IR spectrum revealed the presence of hydroxy Received: February 26, 2016 Published: October 7, 2016 2439

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Chart 1

(3465 cm−1) and carbonyl (1703 and 1661 cm−1) groups. The 13 C NMR data of 1 (Table 1) showed 37 carbon signals due to 12 sp2 nonprotonated carbons, six sp2 methines, three sp3 quaternary carbons, four sp3 methines, six sp3 methylenes, and six sp3 methyls. The 1H NMR data of 1 (Table 2) revealed the presence of three aromatic signals [δ 6.36 (H-8′), 6.32 (H-6′), and 6.25 (H-3′)], three olefinic protons [δ 5.79 (H-3″), 5.44 (H-6), and 5.31 (H-14)], four tertiary methyls [δ 0.88 (Me20), 1.03 (Me-18), 1.02 (Me-19), and 1.93 (Me-16)], two methoxy groups (δ 3.72 and 3.83), and 16 aliphatic protons in the δ 0.9−3.9 range. A detailed analysis of the 1H and 13C NMR spectroscopic data disclosed a 5,7-dihydroxychromen-4one moiety [δH 6.36 (H-8′), 6.25 (H-3′), and 6.32 (H-6′); δC 165.9 (s, C-2′), 109.4 (d, C-3′), 181.5 (s, C-4′), 161.9 (s, C-5′), 99.0 (d, C-6′), 165.9 (s, C-7′), 92.3 (d, C-8′), 157.5 (s, C-9′), and 105.3 (s, C-10′)]. Proton signals at δ 5.79 (s, H-3″) and 3.72 (OMe-4″) and 13C NMR signals at δ 192.2 (s, C-2″), 111.1 (d, C-3″), 160.4 (s, C-4″), and 193.5 (s, C-5″) suggested the presence of a 2-methoxycyclohexene-1,4-dione moiety. A spin system of δ 3.81 (H-6″)/2.02 (H-15)/2.73 (H-15)/5.31 (H-14) and long-range couplings of δ 5.31 (H-14)/1.93 (H16)/3.30 (H-12)/3.81 (H-6″) were observed in 1H−1H COSY and TOCSY experiments, indicating the presence of a partial structure of CH−C(CH3)CH−CH2−CH. This partial structure and the 2-methoxycyclohexene-1,4-dione moiety were also connected through a quaternary carbon, as evidenced by HMBC correlations (Figure 1): H-3″, 6″, 15/C-1″; H-3″, 6″/C-2″; H-12, 14/C-6″; H-3″, 6″, 15/C-5″. Additional spin systems of δ 2.40 (H-10)/0.90 (H-1a)/1.38 (H-1b)/1.47 (H2a)/1.57 (H-2b)/1.15 (H-3a)/1.1.38 (H-3b) and δ 5.44 (H-

6)/2.19 (H-7)/2.40 (H-8), together with three methyl singlets at δ 0.88, 1.02, and 1.03, suggested the presence of a trimethyloctahydronaphthalene moiety, which was confirmed by COSY and TOCSY experiments. The HMBC cross-peak from methine H-7 to C-17 (δC 178.8) indicated the location of a carboxylic group at C-8. Cross-peaks from δ 1.24/1.90 (H211) to C-8, C-10, C-1″, and C-13 indicated that C-11 was linked to C-9 and C-12; cross-peaks from δ 5.79 (H-3″) to C1″ and from H-6″ to C-2′ suggested the connection of C-2′ and C-1″. The NOESY spectrum of 1 showed correlations of H-8/10 with H-11 and H-19, indicating that these hydrogens occupy the same face of the trimethyloctahydronaphthalene ring. The correlations of H-6″ to H-3′ and H-11 revealed that these hydrogens are in close spatial proximity. Therefore, the 2D structure of 1 was established. The absolute configurations were determined by X-ray crystallographic analysis using a Nonius CCD diffractometer equipped with Cu radiation (λ = 1.541 78 Å). Figure 2 shows the ORTEP drawing of 1 with an absolute configuration of (8S, 9S, 10S, 12R, 1″S, and 6″R). The ECD spectrum of 1 showed negative, positive, and negative Cotton effects at 294, 269, and 249 nm, respectively. Diplomeroterpenoids B (2), C (3), and D (4) showed characteristic 1H and 13C NMR signals of a 4H-chromen-4-one moiety and a diterpenoid unit, corresponding to the framework of meroterpenoid 1. HRESIMS analyses indicated that compounds 2, 3, and 4 had molecular formulas of C36H40O9, C37H42O8, and C36H40O8, respectively. The 1H NMR spectrum of 2 showed three aromatic protons at δ 6.17 (s, H-3′), 6.19 (d, J = 1.8 Hz, H-6′), and 6.29 (d, J = 1.8 Hz, H-8′), suggesting the presence of a 5′,7′-dihydroxy-4H-chromen-4-one moiety. The 2440

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Table 1. 13C NMR Data (150 MHz) for Compounds 1−6 (δ in ppm)a position 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2′ 3′ 4′ 5′ 6′ 7′ 8′ 9′ 10′ 7′-OCH3 1‴ 2″ 3″ 4″ 5″ 6″ 4″-OCH3 a

1

2

3

4

5

6

δC, type

δC, type

δC, type

δC, type

δC, type

δC, type

26.9, 22.0, 40.6, 36.3, 145.9, 114.7, 27.2, 45.5, 36.4, 40.0, 37.1, 40.3, 140.9, 121.0, 26.0, 25.6, 178.8, 29.5, 28.5, 18.7, 165.9, 109.4, 181.5, 161.9, 99.0, 165.9, 92.3, 157.5, 105.3, 55.9, 62.8, 192.2, 111.1, 160.4, 193.5, 43.0, 56.6,

CH2 CH2 CH2 C C CH CH2 CH C CH CH2 CH C CH CH2 CH3 C CH3 CH3 CH3 C CH C C CH C CH C C CH3 C C CH C C CH CH3

28.0, 23.2, 42.0, 37.2, 147.1, 116.4, 28.4, 46.8, 37.7, 41.6, 38.4, 41.7, 141.5, 122.7, 26.8, 26.1, 178.7, 30.0, 29.0, 19.4, 167.9, 109.8, 182.8, 163.2, 100.7, 166.7, 95.1, 159.1, 105.1,

CH2 CH2 CH2 C C CH CH2 CH C CH CH2 CH C CH CH2 CH3 C CH3 CH3 CH3 C CH C C CH C CH C C

64.1, 194.1, 112.1, 162.4, 195.2, 44.6, 57.4,

C C CH C C CH CH3

27.0, 22.0, 40.6, 36.3, 145.9, 114.7, 27.1, 45.5, 36.7, 40.2, 37.4, 40.2, 141.0, 120.9, 26.0, 25.6, 177.3, 29.5, 28.5, 18.5, 164.9, 111.0, 176.9, 127.0, 115.5, 164.4, 100.0, 157.8, 117.3, 56.5, 62.8, 192.6, 111.0, 160.3, 193.7, 43.1, 56.0,

CH2 CH2 CH2 C C CH CH2 CH C CH CH2 CH C CH CH2 CH3 C CH3 CH3 CH3 C CH C CH CH C CH C C CH3 C C CH C C CH CH3

27.2, 22.0, 40.6, 36.3, 145.9, 114.5, 26.9, 45.9, 36.8, 40.1, 37.7, 40.6, 140.5, 121.1, 26.0, 25.8, 178.8, 29.5, 28.5, 18.7, 165.1, 110.5, 177.2, 127.5, 115.7, 161.9, 102.9, 157.7, 116.9,

CH2 CH2 CH2 C C CH CH2 CH C CH CH2 CH C CH CH2 CH3 C CH3 CH3 CH3 C CH C CH CH C CH C C

28.8, 22.9, 42.0, 37.3, 147.9, 116.3, 28.2, 47.5, 38.7, 41.6, 37.2, 42.3, 143.4, 121.5, 26.7, 26.7, 178.4, 30.1, 29.2, 18.6, 167.7, 109.9, 183.2, 163.1, 100.9, 166.9, 95.1, 159.2, 105.1,

CH2 CH2 CH2 C C CH CH2 CH C CH CH2 CH C CH CH2 CH3 C CH3 CH3 CH3 C CH C C CH C CH C C

27.4, 21.8, 40.6, 36.3, 146.3, 115.1, 27.1, 45.5, 37.6, 40.0, 35.5, 40.9, 142.7, 119.5, 25.8, 26.2, 178.5, 29.5, 28.6, 18.1, 165.4, 110.1, 177.5, 127.1, 116.0, 162.6, 102.7, 157.8, 116.1,

CH2 CH2 CH2 C C CH CH2 CH C CH CH2 CH C CH CH2 CH3 C CH3 CH3 CH3 C CH C CH CH C CH C C

62.8, 192.7, 111.2, 160.2, 194.1, 43.0, 56.6,

C C CH C C CH CH3

64.5, 194.4, 112.2, 162.6, 195.0, 44.1, 57.4,

C C CH C C CH CH3

63.3, 192.8, 111.4, 160.6, 194.0, 42.8, 56.6,

C C CH C C CH CH3

Compounds 1, 3, 4, and 6 were measured in CDCl3; 2 and 5 were measured in methanol-d4.

6″ (δ 4.01) and H-8 (δ 2.67) appeared at a lower field than those of 1 (δ 3.81, H-6″; δ 2.40, H-8), which was caused by the configuration change. The NOESY spectrum of 5 showed correlations of H-8/H-10 with H-11 and H-19, as well as correlations of H-6″ with H-3′ and H-11. In contrast to the ECD spectrum of 1 with negative, positive, and negative Cotton effects at 294, 269, and 249 nm, respectively, the ECD spectrum of 5 showed positive, negative, and positive Cotton effects at 296, 271, and 250 nm, respectively. The absolute configuration of 5 was defined as (8S, 9S, 10S, 12S, 1″R, 6″S) by X-ray crystallographic analysis, and its ORTEP diagram is shown in Figure 2. Diplomeroterpenoid F (6) showed the same UV spectrum as 5 and gave the molecular formula C36H40O8 (m/z 601.2794 [M + H]+, calcd for C36H41O8, 601.2801) with one oxygen atom fewer than that of 5. A comparison of the 13C and 1H NMR data of 5 and 6 (Tables 1 and 2) suggests that they differed in the 4H-chromen-4-one moiety. The 1H NMR spectrum of the aromatic region of 6 showed four aromatic protons at δ 6.39 (s, H-3′), 6.73 (2H, m, H-6′/8′), and 7.74 (d, J = 7.5 Hz, H-5′),

H NMR spectrum of 3 showed four aromatic protons at δ 6.33 (s, H-3′), 6.94 (dd, J = 9.0, 2.4 Hz, H-6′), 8.01 (d, J = 9.0 Hz, H-5′), and 6.80 (d, J = 2.4 Hz, H-8′) and a methoxy group (δ 3.88), indicating the presence of a 7′-methoxy-4H-chromen-4one moiety. The 1H NMR spectrum of 4 showed four aromatic protons at δ 6.33 (s, H-3′), 6.92 (d, J = 9.0 Hz, H-6′), 8.01 (d, J = 9.0 Hz, H-5′), and 6.95 (s, H-8′), suggesting the presence of a 7′-hydroxy-4H-chromen-4-one moiety. These structures were confirmed by analyses of the HMQC, HMBC, and NOESY spectra. On the basis of the evidence of the specific rotations and ECD spectra, it was deduced that 2−4 possessed the same absolute configurations as 1. Compared to 1, diplomeroterpenoid E (5) had the same UV and similar IR spectra, but showed a specific rotation of [α]26D +173 with an opposite sign. HRESIMS data indicated that the molecular formula of 5 was C36H40O9 with one carbon and two hydrogen atoms fewer than 1. A comparison of the 13C and 1H NMR spectra of 5 (Tables 1 and 2) with those of 1 suggested that a hydroxy group in 5 instead of a methoxy group in 1 was located at C-7′. In the 1H NMR spectrum of 5, the signals of H1

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Table 2. 1H NMR Data (600 MHz) for Compounds 1−6 (δ in ppm and J in Hz)a position 1a 1b 2a 2b 3a 3b 6 7 8 10 11a 11b 12 14 15a 15b 16 18 19 20 3′ 5′ 6′ 8′ 7′-OCH3 3″ 6″ 4″-OCH3 a

1

2

0.90, 1.38, 1.47, 1.57, 1.15, 1.38, 5.44, 2.19, 2.40, 2.40, 1.24, 1.90, 3.30, 5.31, 2.02, 2.73, 1.93, 1.03, 1.02, 0.88, 6.25,

mb m m m td (13.2, 3.0) m brs m m m d (12.6) t (13.8) d (10.2) d (6.0) m dd (18.6, 11.4) s s s s s

0.95, 1.41, 1.45, 1.60, 1.17, 1.41, 5.46, 2.17, 2.42, 2.42, 1.26, 2.01, 3.30, 5.35, 2.07, 2.78, 1.92, 1.03, 1.06, 0.91, 6.17,

6.32, 6.36, 3.83, 5.79, 3.81, 3.72,

d (2.0) d (2.0) s s m s

6.19, d (1.8) 6.29, d (1.8)

m d (12.6) m m td (14.4, 3.0) m s m m m d (13.2) m db d (6.0) m dd (18.6, 11.4) s s s s s

5.96, s 3.80, dd (10.8, 5.4) 3.75, s

3 0.87, 1.38, 1.46, 1.55, 1.12, 1.38, 5.43, 2.19, 2.40, 2.40, 1.30, 1.89, 3.22, 5.33, 2.05, 2.74, 1.95, 1.01, 1.01, 0.86, 6.33, 8.01, 6.94, 6.80, 3.88, 5.78, 3.86, 3.71,

4

mb d (10.8) m m td (13.2, 3.0) d (13.8) s m m m d (12.6) t (13.8) d (10.2) d (6.0) m dd (18.6, 11.4) s s s s s d (9.0) dd (9.0, 2.4) d (2.4) s s m s

0.91, 1.44, 1.53, 1.58, 1.14, 1.39, 5.42, 2.12, 2.41, 2.41, 1.32, 1.88, 3.29, 5.34, 2.05, 2.72, 1.95, 1.02, 1.01, 0.85, 6.33, 8.01, 6.92, 6.95,

m d (10.8) m m td (13.8, 3.0) d (15.0) s m/2.20, m m m d (12.6) t (12.6) d (10.8) d (4.8) m dd (18.6, 11.4) s s s s s d (9.0) d (9.0) s

5.80, s 3.91, m 3.71, s

5 0.93, 1.74, 1.44, 1.55, 1.17, 1.44, 5.54, 2.15, 2.67, 2.39, 1.31, 1.88, 3.42, 5.44, 2.15, 2.87, 1.94, 1.05, 0.98, 0.85, 6.20,

6

mb d (10.8) m m td (13.2, 3.0) m d (6.0) m/2.25, m m d (12.6) d (12.6) t (12.6) d (12.6) d (5.4) m dd (19.2, 11.4) s s s s s

mb d (10.5) m m td (12.5, 3.0) m s m m d (12.0) m t (13.5) d (11.5) d (6.0) d (13.5) dd (18.6, 11.4) s s s s s d (7.5) m m

6.17, d (1.8) 6.22, d (1.8)

0.94, 1.62, 1.37, 1.53, 1.15, 1.37, 5.51, 2.25, 2.73, 2.35, 1.37, 1.85, 3.43, 5.41, 2.13, 2.90, 1.98, 1.04, 0.95, 0.85, 6.39, 7.74, 6.73, 6.73,

5.96, s 4.01, dd (11.4, 5.4) 3.75, s

5.80, s 4.06, dd (10.0, 5.0) 3.71, s

Compounds 1, 3, 4, and 6 were measured in CDCl3; 2 and 5 were measured in methanol-d4. bSignal partially obscured.

and 6.87 (H-3), 7.59 (H-2), 7.75 (H-6)] and a trans double bond [δ 7.67 (H-8′) and 7.83 (H-9′)]. The four protons of an aromatic A2B2 spin system [δ 6.76 (H-3″, -5″) and 7.19 (H-2″, -6″)] were also observed. The 1H−1H COSY correlations of δ 5.55 (d, J = 6.0 Hz, H-7″)/3.53 (m, H-8″)/3.86, 3.88 (m, H29″) and the 13C NMR signals at δ 166.4 (s, C-4), 109.1 (s, C5), 89.4 (d, C-7″), 54.3 (d, C-8″), and 65.8 (t, C-9″) suggested the presence of a (2,3-dihydrofuran-3-yl)methanol moiety. The HMBC cross-peaks of H-6′/H-8′/H-9′ with C-7′, H-3′/H-5′ with C-1′, H-8′/H-3 with C-1, H-2/H-6/H-7″/H-8″ with C-4, H-3/H-8″/H2-9″ with C-5, and H-3″/H-5″/H-7″/H-8″ with C-1″ confirmed the structure shown as 7. The 1H and 13C NMR data of the (2,3-dihydrofuran-3-yl)methanol moiety as well as the coupling constants of H-7″ and H-8″ were similar to those of the trans-(2,3-dihydrofuran-3-yl)methanol moiety in silychristin, a dihydroflavonol lignoid.15 Hence, the relative configuration of C-7″, C-8″ was determined to be trans. The ECD spectrum of 7 ([nm (Δε): 265 (+0.3) and 231 (−0.1)]) proved the (7S, 8R) absolute configuration by comparison with the ECD data of (+) licarin A (positive and negative Cotton effects at 268 and 231 nm, respectively).16 The semipreparative HPLC separation of subfraction 15D-1 gave a mixture of 8 and 9. The 1H NMR spectrum of the mixture showed the presence of two sets of signals. The ratio of 8 and 9 was determined to be approximately 1:1 by a comparison of the proton signal integration. The ESIMS spectrum showed two deprotonated molecular ions at m/z 449 [M − H]− and 463 [M − H]−. The molecular formulas were determined as C25H22O8 for 8 and C25H20O9 for 9 based on an HRESIMS analysis (8: m/z 449.1230 [M − H]−, calcd for

Figure 1. HMBC correlations of compound 1.

indicating a 7′-hydroxy-4H-chromen-4-one moiety. Similar to the signals in 5, the signals of H-6″ at δ 4.06 (dd, J = 10.8/5.4 Hz) and H-8 at δ 2.73 (m) in 6 appeared at lower fields than those of 1. Furthermore, the ECD spectra of 5 and 6 showed similar Cotton effects. Therefore, the absolute configuration was deduced as (8S, 9S, 10S, 12S, 1″R, 6″S). Diplochalcolin A (7) has a molecular formula of C24H20O6 based on HRESIMS analysis (m/z 405.1323 [M + H]+, calcd for C24H20O6, 405.1338). The 13C NMR spectrum of 7 showed 24 carbon signals due to nine sp2 nonprotonated carbons (five oxygenated), 12 sp2 methines, two sp3 methines, and one oxygenated sp3 methylene. The 1H NMR spectrum of 7 revealed the presence of a chalcone moiety with two sets of ABX aromatic protons [δ 6.28 (H-3′), 6.41 (H-5′), 7.99 (H-6′) 2442

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Figure 2. ORTEP drawings of compounds 1 and 5.

C25H21O8, 449.1236; 9: m/z 463.1034 [M − H]−, calcd for C25H19O9, 463.1029). Analysis of the 1H NMR data showed that compound 9 was hydnocarpin.7 The 1H NMR signals derived from 8 included three sets of aromatic ABX spin systems [δ 6.29 (H-3′)/6.42 (H-5′)/7.98 (H-6′), δ 7.30 (H2)/7.40 (H-6)/6.97 (H-3), and δ 6.85 (H-5″)/6.91 (H-6″)/ 7.02 (H-2″)], a trans double bond [δ 7.67 (H-8′) and 7.83 (H9′)], two oxygenated aliphatic methines [δ 4.97 (H-7″) and 4.10 (H-8″)], an oxymethylene (δ 3.51/3.73), and a methoxy (δ 3.87) signal. Two sets of aromatic ABX spin systems [δ 6.29 (H-3′)/6.42 (H-5′)/7.98 (H-6′), δ 7.30 (H-2)/7.40 (H-6)/ 6.97 (H-3)] and the trans double-bond signals revealed the presence of a chalcone moiety as in 7, which was further confirmed by the HMBC data. The 1H−1H COSY correlations of δ 4.97 (d, H-7″)/4.10 (m, H-8″)/3.51(m, Ha-9″)/3.73 (m, Hb-9″) and the 13C NMR signals at δ 147.9 (s, C-4), 145.3 (s, C-5), 78.2 (d, C-7″), 79.9 (d, C-8″), and 62.0 (t, C-9″) suggested the presence of a (2,3-dihydro-1,4-dioxin-2-yl)methanol moiety. A third aromatic ABX spin system [δ 6.85 (d, H-5″)/6.91 (dd, H-6″)/7.02 (d, H-2″)] and the methoxy protons were derived from a 4-hydroxy-3-methoxyphenyl group, which was deduced from the 1H−1H COSY and NOESY spectra. The analysis of the HMBC cross-peaks of H-6′ with C-2′/C-4′/C-7′, H-3′/H-5′ with C-1′/, H-9′ with C-7′/C2/C-6, H-3 with C-1/C-5, H-2 with C-4/C-6, H-7″ with C-2″/ C-6″, H-5″ with C-1″/C-3″, and −OCH3 with C-3″ confirmed structure 8, referred to as diplochalcolin B. The relative configuration between H-7″ and H-8″ was determined as trans by the large coupling constant (J7″, 8″ = 8.4 Hz) as that of hydnocarpin.7,17 Compounds 1−6 were evaluated for their inhibitory effects on PFTase (Table 3). FTase inhibitor II, a potent PFTase inhibitor, was used as the positive control. Compounds 1−3 and 5 showed moderate inhibitory activity with IC50 values of

Table 3. Inhibition of Protein Farnesyl Transferase of Compounds 1−6a compound 1 2 3 4 5 6 FTase inhibitor IIb

IC50 (μM) 5.0 8.5 7.5 47.0 5.1 27.9 0.1

± ± ± ± ± ± ±

0.0 0.1 0.1 1.5 0.1 1.5 0.0

The values represent the mean ± SD of three independent experiments. bReported IC50 value of FTase inhibitor II is 50−75 nM.21 a

5.0−8.5 μM, while 6 and 4 were inactive. The results indicated that the 5′-hydroxy substitution in the meroterpenoid skeleton was essential for the stronger activities and that the replacement of 7′-hydroxy by 7′-methoxy could enhance these activities. Compounds 1−6 were also evaluated for their antiproliferation activity against a panel of human tumor cell lines, including A549 (lung carcinoma), AGS (gastric adenocarcinoma), HepG2 (hepatoblastoma), HT29 (colorectal adenocarcinoma), and PC3 (prostate carcinoma). Compound 1 showed growth inhibition activity against HepG2 cells with a GI50 value of approximately 8.6 μM, while the GI50 values of compounds 2− 6 were greater than 10 μM.

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EXPERIMENTAL SECTION

General Experiment Procedures. Optical rotations were measured on a JASCO DIP-370 polarimeter. UV spectra were measured on a Hitachi U-3200 spectrophotometer. ECD spectra were obtained on a JASCO J-715 spectrometer. IR spectra were obtained on a Nicolet Avatar 320 IR spectrometer. 1H, 13C, and 2D NMR spectra were measured on a Varian VNMRS600 spectrometer with deuterated 2443

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methods and refined by full-matrix least-squares on F2 values. The final indices were R1 = 0.0799, wR2 = 0.2036 with goodness-of-fit = 1.069. Diplomeroterpenoid B (2): [α]26D −125 (c 0.5, MeOH); UV (MeOH) λmax (log ε) 255 (4.08) nm; ECD [nm (Δε)] (2.6 mg/50 mL MeOH) 357 (−0.5), 324 (+0.6), 295 (−2.6), 269 (+10.1), 248 (−8.9), 227 (−4.7), 206 (−12.4); IR (KBr) νmax 3432, 1722, 1659, 1607, 1443, 1352, 1155, 1108 cm−1; 1H NMR (methanol-d4, 600 MHz) see Table 1; 13C NMR (methanol-d4, 150 MHz) see Table 2; ESIMS m/z 615 [M − H]−; HRESIMS m/z 617.2745 [M + H]+ (calcd for C36H41O9, 617.2751). Diplomeroterpenoid C (3): [α]26D −82 (c 0.4, MeOH); UV (MeOH) λmax (log ε) 281 (4.06) nm; ECD [nm (Δε)] (3.2 mg/50 mL MeOH) 307 (−0.3), 288 (+6.5), 273 (−0.5), 260 (+4.3), 241 (−6.1), 234 (−4.8), 211 (−8.4); IR (KBr) νmax 3429, 1705, 1625, 1604, 1439, 1376, 1366, 1204, 1165, 1089 cm−1; 1H NMR (CDCl3, 600 MHz) see Table 1; 13C NMR (CDCl3, 150 MHz) see Table 2; ESIMS m/z 613 [M − H]−; HRESIMS m/z 615.2970 [M + H]+ (calcd for C37H43O8, 615.2958). Diplomeroterpenoid D (4): yellow, microcrystalline from MeOH; mp 170 °C; [α]26D −52 (c 0.4, MeOH); UV (MeOH) λmax (log ε) 250 (3.70), 277 sh (3.58) nm; IR (KBr) νmax 3469, 1705, 1624, 1375, 1085 cm−1; ECD [nm (Δε)] (2.9 mg/50 mL MeOH) 308 (+0), 291 (+1.4), 276 (+0.3), 261 (+2.5), 244 (−2.4), 236 (−1.8), 223 (−3.5), 212 (−3.7); 1H NMR (CDCl3, 600 MHz) see Table 1; 13C NMR (CDCl3, 150 MHz) see Table 2; ESIMS m/z 599 [M − H]−; HRESIMS m/z 601.2804 [M + H]+ (calcd for C36H41O8, 601.2801). Diplomeroterpenoid E (5): [α]26D +173 (c 0.5, MeOH); UV (MeOH) λmax (log ε) 256 (4.16) nm; ECD [nm (Δε)] (2.7 mg/50 mL MeOH) 363 (+2.2), 321 (−0.3), 296 (+1.3), 271 (−9.2), 250 (+10.0), 241 (+6.3), 216 (−2.5); IR (KBr) νmax 3465, 1703, 1661, 1606, 1443, 1410, 1356, 1208, 1172, 1097, 1026 cm−1; 1H NMR (methanol-d4, 600 MHz) see Table 1; 13C NMR (methanol-d4, 150 MHz) see Table 2; ESIMS m/z 615 [M − H]−; HRESIMS m/z 617.2754 [M + H]+ (calcd for C36H41O9, 617.2751). X-ray Structure Analysis of Diplomeroterpene E (5).18 A suitable colorless crystal (0.25 × 0.20 × 0.15 mm3), grown by slow evaporation of a MeOH solution, was mounted on a Nonius CCD diffractometer equipped with Cu radiation (λ = 1.541 78 Å). Crystal data: C38H48O11, Mr = 680.76 g/mol, orthorhombic. Cell parameters: a = 7.72090(10), b = 15.8528(3), c = 28.9225(5) Å, V = 3540.05(10) Å3, space group P212121 (Z = 4), Dcalc = 1.277 mg/m3, F(000) = 1456. A total of 12 264 reflections were collected (6451 unique, Rint = 0.0232) in the range 3.06° < θ < 67.96°. The structure was solved using direct methods and refined by full-matrix least-squares on F2 values. The final indices were R1 = 0.0515, wR2 = 0.1444 with goodness-of-fit = 0.989. Diplomeroterpenoid F (6): [α]26D +235 (c 0.4, MeOH); UV (MeOH) λmax (log ε) 240 sh (4.13), 278 (4.04) nm; ECD [nm (Δε)] (2.9 mg/50 mL MeOH) 340 (+2.8), 316 (+0.4), 306 (+0.7), 265 (−7.5), 244 (+9.8), 229 (+6.4), 221 (+7.9), 207 (+2.3); IR (KBr) νmax 3433, 1709, 1668, 1645, 1464, 1381, 1322, 1209, 1175 cm−1; 1H NMR (CDCl3, 600 MHz) see Table 1; 13C NMR (CDCl3, 150 MHz) see Table 2; ESIMS m/z 599 [M − H]−; HRESIMS m/z 601.2794 [M + H]+ (calcd for C36H41O8, 601.2801). Diploflavolin A (7): [α]26D 0 (c 0.2, MeOH); UV (MeOH) λmax (log ε) 371 (3.87) nm; IR (KBr) νmax 3433, 1709, 1668, 1645, 1464, 1381, 1322, 1209, 1175 cm−1; ECD [nm (Δε)] (0.8 mg/25 mL MeOH) 265 (+0.3), 259 (+0.2), 238 (+0.4), 231 (−0.1), 222 (+0.4); 1 H NMR (600 MHz, methanol-d4) δ 3.53 (1H, m, H-8″), 3.86 (1H, m, H-9″a), 3.88 (1H, m, H-9″b), 5.55 (1H, d, J = 6.0 Hz, H-7″), 6.28 (1H, d, J = 2.4 Hz, H-3′), 6.41 (1H, dd, J = 2.4, 9.0 Hz, H-5′), 6.76 (2H, d, J = 9.0 Hz, H-3″, 5″), 6.87 (1H, d, J = 8.4 Hz, H-3), 7.19 (2H, d, J = 9.0 Hz, H-2″, 6″), 7.59 (1H, dd, J = 1.8, 8.4 Hz, H-2), 7.67 (1H, d, J = 15.6 Hz, H-8′), 7.75 (1H, d, J = 1.8 Hz, H-6), 7.83 (1H, d, J = 15.6 Hz, H-9′), 7.99 (1H, d, J = 9.0 Hz, H-6′); 13C NMR (150 MHz, methanol-d4) δ 54.3 (C-8″), 64.8 (C-9″), 89.4 (C-7″), 103.8 (C-3′), 109.1 (C-5′), 110.7 (C-3), 114.7 (C-1′), 116.4 (C-3″, 5″), 118.7 (C8′), 126.3 (C-6), 128.3 (C-2″, 6″), 129.5 (C-1), 130.6 (C-5), 132.4 (C-2), 133.4 (C-6′), 133.7 (C-1″), 145.7 (C-9′), 158.7 (C-4″), 163.9 (C-4), 166.4 (C-4′), 167.6 (C-2′), 193.5 (C-7′); ESIMS m/z 403 [M

solvents as internal standards. ESIMS and HRESIMS data were recorded on Finnigan LCQ and Finnigan/Thermo Quest MAT spectrometers, respectively. HPLC analysis was performed using a Shimadzu LC-8A pump and SPD-10A vp UV−vis detector. A Cosmosil 5C18-AR-II column (20 × 250 mm; particle size 5 μm; Nacalai tesque, Kyoto, Japan) was used for separation. The X-ray data were acquired on a Nonius Kappa CCD single-crystal X-ray diffractometer. Plant Material. The whole plant of Mimosa diplotricha was collected from Taitung County, Taiwan, in May 2009 and identified by Dr. Cheng-Jen Chou, Research Fellow, National Research Institute of Chinese Medicine, Taipei, Taiwan. A voucher specimen (NHP01474) was deposited in the Herbarium of the National Research Institute of Chinese Medicine, Ministry of Health and Welfare, Taipei, Taiwan. Extraction and Isolation. Roots of M. diplotricha (1.8 kg) were crushed and extracted with EtOH (3 × 40 L) under reflux. After removal of the solvent, the extract (195 g) was suspended in H2O (1 L) and extracted successively with CHCl3 and n-BuOH (each 3 × 1 L). The CHCl 3 fraction (42 g) was subjected to column chromatography on silica gel (5 × 75 cm) and was eluted with a solvent mixture of EtOAc/n-hexane (in ratios of 10, 20, 30, 40, 70, 90, and 100%, each 4 L) and then with 5 and 10% MeOH/CHCl3 to give 23 fractions (Frs. 1−23). β-Sitosterol (20, 110 mg), hernancorizin (15, 9 mg), and β-sitosterol glucoside (21, 794 mg) precipitated from Frs. 5, 14, and 20, respectively. The filtrate of Fr. 14 (95 mg) was chromatographed by semipreparative HPLC (column: Cosmosil 5C18-AR-II, 20 × 250 mm, 5 μm, solvent: 35% CH3CN/H2O, flow rate: 4.7 mL/min) to yield 7-hydroxy-8-methoxychromone (17, 10 mg), 2′-hydroxy-3,7,8,4′,5′-pentamethoxyflavone (14, 11 mg), and diplotrin B (13, 5 mg). Fr. 15 (1.12 g) was chromatographed on a Sephadex-LH-20 column (4.8 × 80 cm) with 5% CHCl3/MeOH as eluent to give eight subfractions, 15A−15H. Frs. 15C (109 mg) and 15D (398 mg) were individually chromatographed by semipreparative HPLC (column: Cosmosil 5C18-AR-II, 20 × 250 mm, 5 μm, solvent: 70% CH3CN/H2O, flow rate: 4.7 mL/min) to give 3 (14 mg) and 1 (12 mg) from Fr. 15C and subfraction 15D-1 (127 mg) and 2 (8 mg) and 5 (20 mg) from Fr. 15D. Subfraction 15D-1 was further chromatographed by semipreparative HPLC (50−75% MeOH/H2O over 30 min, flow rate: 3.7 mL/min) to give 7 (2 mg), a mixture of 8 and 9 (4 mg), and 12 (5 mg). A precipitate was separated from Fr. 16 and recrystallized from MeOH/CHCl3 to give diplotasin (16, 22 mg). The filtrate of Fr. 16 (565 mg) was chromatographed on a Sephadex LH-20 column (4.8 × 80 cm) with 5% CHCl3/MeOH as the eluent to give nine subfractions, 16A−16I. Fr. 16C (144 mg) was chromatographed by semipreparative HPLC (column: Cosmosil 5C18-AR-II, 20 × 250 mm, 5 μm, solvent: 70% CH3CN/H2O, flow rate: 4.7 mL/min) to give 6 (32 mg), 4 (4 mg), and 18 (4 mg). Precipitates of diplotasin (16, 29 mg), chrysoeriol (11, 3 mg), and 7,4′-dihydroxyflavone (10, 9 mg) were individually separated from Frs. 16E, 16F, and 16H. Fr. 17 (464 mg) was chromatographed on a Sephadex LH-20 column (3 × 50 cm), eluting with 5% CHCl3/MeOH, to give diplotasin (16, 28 mg) and 4-hydroxy-3,5-dimethoxybenzoic acid (19, 18 mg). Diplomeroterpenoid A (1): [α]26D −173 (c 0.4, CHCl3); UV (MeOH) λmax (log ε) 255 (4.43) nm; ECD [nm (Δε)] (2.9 mg/50 mL MeOH) 356 (−1.0), 323 (+1.5), 294 (−5.1), 269 (+23.0), 249 (−19.6), 229 (−10.3), 214 (−17.7); IR (KBr) νmax 3534, 3400, 1707, 1660, 1609, 1433, 1344, 1205, 1160, 1113, 1080 cm−1; 1H NMR (CDCl3, 600 MHz) see Table 1; 13C NMR (CDCl3, 150 MHz) see Table 2; ESIMS m/z 629 [M − H]−; HRESIMS m/z 631.2914 [M + H]+ (calcd for C37H43O9, 631.2907). X-ray Structure Analysis of Diplomeroterpenoid A (1).18 A suitable colorless crystal (0.20 × 0.15 × 0.05 mm3), grown by slow evaporation of a MeOH solution, was mounted on a Nonius CCD diffractometer equipped with Cu radiation (λ = 1.541 78 Å). Crystal data: C37H46O11, Mr = 666.74 g/mol, orthorhombic. Cell parameters: a = 10.4620(11) Å, b = 12.5584(8) Å, c = 26.2046(19) Å, V = 3442.9(5) Å3, space group P212121 (Z = 4), Dcalc = 1.286 mg/m3, F(000) = 1424. A total of 7104 reflections were collected (4821 unique, Rint = 0.0913) in the range 3.90° < θ < 67.99°. The structure was solved using direct 2444

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− H]−; HRESIMS m/z 405.1326 [M + H]+ (calcd for C24H21O6, 405.1338). Diploflavolin B (8): 1H NMR (600 MHz, methanol-d4) δ 3.51 (1H, m, H-9″a), 3.73 (1H, t, J = 14.4 Hz, H-9″b), 3.87 (3H, s, 3″-OCH3), 4.10 (1H, m, H-8″), 4.97 (1H, d, J = 8.4 Hz, H-7″), 6.29 (1H, d, J = 2.4 Hz, H-3′), 6.42 (1H, dd, J = 2.4, 8.4 Hz, H-5′), 6.85 (1H, d, J = 8.4 Hz, H-5″), 6.91 (1H, dd, J = 1.8, 8.4 Hz, H-6″), 6.97 (1H, d, J = 8.4 Hz, H-3), 7.02 (1H, d, J = 1.8 Hz, H-2″), 7.30 (1H, dd, J = 2.4, 8.4 Hz, H-2), 7.40 (1H, d, J = 2.4 Hz, H-6), 7.65 (1H, d, J = 15.6 Hz, H-8′), 7.77 (1H, d, J = 15.6 Hz, H-9′), 7.98 (1H, d, J = 8.4 Hz, H-6′); 13C NMR (150 MHz, methanol-d4) δ 56.5 (3″-OCH3), 62.0 (C-9″), 78.2 (C-7″), 79.9 (C-8″), 103.8 (C-3′), 109.2 (C-5′), 112.1 (C-2″), 114.7 (C-1′), 116.3 (C-5″), 118.1 (C-6), 118.6 (C-3), 119.9 (C-8′), 121.7 (C-6″), 123.7 (C-2), 129.1 (C-1″), 130.1 (C-1), 133.5 (C-6′), 145.1 (C-9′), 145.3 (C-5), 147.9 (C-4), 148.5 (C-4″), 149.3 (C-3″), 166.6 (C-4′), 167.6 (C-2′), 193.4 (C-7′); ESIMS m/z 449 [M − H]−; HRESIMS m/z 449.1230 [M − H]− (calcd for C25H21O8, 449.1236). Cell Cultures and Reagents. Human lung carcinoma A549 cells (BCRC 60074), human gastric adenocarcinoma AGS cells (BCRC 60102), human hepatoblastoma HepG2 cells (BCRC 60025), human colorectal adenocarcinoma HT-29 cells (BCRC 67003), and human prostate carcinoma PC3 cells (BCRC 60122) were obtained from the Bioresources Collection and Research Center (BCRC), Hsin-Chu, Taiwan. All cell lines were maintained in RPMI 1640 medium supplemented with 10% fetal bovine serum (FBS), nonessential amino acid, 100 units/mL penicillin, and 100 units/mL streptomycin. Cultures were maintained in a humidified incubator at 37 °C in 5% CO2/95% air. Cell culture reagents were obtained from Invitrogen (Rockville, MD, USA). Sulforhodamine B (SRB), trichloroacetic acid (TCA), doxorubicin, and other chemicals were purchased from Sigma Chemical Co. (St. Louis, MO, USA). Sulforhodamine B Assay. An antiproliferation assay was performed using the SRB assay as previously reported.19 Briefly, cells were seeded on 96-well plates in a medium with 10% FBS. After 24 h, the cells were fixed with 10% TCA (Sigma) to represent the cell population at the time of addition of the test compound (T0). After an additional incubation of DMSO, doxorubicin (as the reference compound), or the test compound for 72 h, the cells were fixed with 10% TCA, and 0.4% SRB solution (in 1% acetic acid) was added for 10 min. The unbound SRB was washed out by 1% HOAc, and the cell-bound SRB was solubilized with 10 mM Tris base. The absorbance was read at a wavelength of 515 nm. Using the following absorbance measurements, including time zero (T0), control growth (C), and cell growth in the presence of test compound (Tx), the percentage of growth was calculated as 100 − [(Tx − T0)/(C − T0)] × 100. The concentration that inhibited 50% of the cancer cell growth activity (GI50) of each compound was then determined. Protein Farnesyl Transferase Assay. The assay was carried out in 384-well microplates with a final volume of 20 μL by a method modified from a previous report.20 Briefly, 10 nM of rat PFTase (Jena Biosciences, Jena, Germany) was incubated with the test compound or DMSO (1%) for 15 min, and the mixture was added to a solution [50 mM Tris-HCl, pH 7.5, 5 mM MgCl2, 5 mM DTT, 0.1 mM ZnCl2, 0.2% octyl-β-D-glucopyranoside (Sigma), 10 μM PFTase substrate dansyl-Gly-Cys-Val-Leu-Ser-OH, and 10 μM farnesyl pyrophosphate (Sigma)] to initiate the reaction. The reaction was incubated at 37 °C for 30 min, and the fluorescence was detected by an M5 plate reader (Molecular Devices, Sunnyvale, CA, USA) at 340 nm excitation and 505 nm emission.

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AUTHOR INFORMATION

Corresponding Author

*Tel (L.-C. Lin): +886-2-28201999, ext. 7101. Fax: +886-228264276. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by a grant from the National Science Council, ROC (NSC 102-2320-B-077-002-MY3). REFERENCES

(1) Huang, T. C.; Ohashi, H. In Leguminosae. Flora of Taiwan, 2nd ed.; Editorial Committee of the Flora of Taiwan: Taipei, 1993; Vol. III, pp 172−174. (2) Chiu, N. Y.; Change, K. H. The Illustrated Medicinal Plants of Taiwan; Southern Materials Center Inc.: Taipei, 1998; Vol. 5, p 99. (3) Lin, L. C.; Chiou, C. T.; Cheng, J. J. J. Nat. Prod. 2011, 74, 2001− 2004. (4) Novelli, G.; D’Apice, M. R. J. Inherited Metab. Dis. 2012, 35, 917− 926. (5) Palsuledesai, C. C.; Distefano, M. D. ACS Chem. Biol. 2015, 10, 51−62. (6) Hottman, D. A.; Li, L. Mol. Neurobiol. 2014, 50, 177−185. (7) Wang, G. J.; Tsai, T. H.; Lin, L. C. Phytochemistry 2007, 68, 2455−2464. (8) Ji, S.; Li, Z.; Song, W.; Wang, Y.; Liang, W.; Li, K.i; Tang, S.; Wang, Q.; Qiao, X.; Zhou, D.; Yu, S.; Ye, M. J. Nat. Prod. 2016, 79, 281−292. (9) Markham, K. R.; Chari, V. M.; Mabry, T. J. . In: Harborne, J. B., Mabry, T. J., Eds.; The Flavonoids: Advances in Research; Chapman and Hall: New York, 1982. (10) Romussi, G.; Ciarallo, G. J. Heterocycl. Chem. 1976, 13, 211− 220. (11) Lin, L. C.; Tsai, W. J.; Chou, C. J. Chin. Pharm. J. 1996, 48, 441−449. (12) Wu, C.; Du, C.; Gubbens, J.; Choi, Y. H.; Van Wezel, G. P. J. Nat. Prod. 2015, 78, 2355−2363. (13) Matsumoto, T.; Shigemoto, T.; Itoh, T. Phytochemistry 1983, 22, 2622−2624. (14) Bayoumi, S. A.; Rowan, M. G.; Beeching, J. R.; Blagbrough, I. S. Phytochemistry 2010, 71, 598−604. (15) Tanaka, H.; Hiroo, M.; Ichino, K.; Ito, K. Chem. Pharm. Bull. 1989, 37, 1441−1445. (16) Nascimento, I. R.; Lopes, L. M. X.; Davin, L. B.; Lewis, N. G. Tetrahedron 2000, 56, 9181−9193. (17) Parthasarathy, M. R.; Ranganathan, K. R.; Sharma, D. K. Phytochemistry 1979, 18, 506−508. (18) Crystallographic data for the structures 1 (CCDC 1507257) and 5 (CCDC 1507258) reported in this paper have been deposited with the Cambridge Crystallographic Data Centre. (19) Chiou, C. T.; Hsu, R. Y.; Lin, L. C. Planta Med. 2014, 80, 1113− 1117. (20) Long, C.; Marcourt, L.; Raux, R.; David, B.; Gau, C.; Menendez, C.; Gao, M.; Laroche, M. F.; Schambel, P.; Delaude, C.; Ausseil, F.; Lavaud, C.; Massiot, G. J. Nat. Prod. 2009, 72, 1804−1815. (21) Manne, V.; Ricca, C. S.; Brown, J. G.; Tuomari, A. V.; Yan, N.; Patel, D.; Schmidt, R.; Lynch, M. J.; Ciosek, C. P.; Carboni, J. M.; Robinson, S.; Gordon, E. M.; Barbacid, M.; Seizinger, B. R.; Biller, S. A. Drug Dev. Res. 1995, 34, 121−137.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jnatprod.6b00170. 1D and 2D NMR data of compounds 1−9; HPLC chromatograms of CHCl3 extracts of Mimosa diplotrichaaerial sample and root sample (PDF) 2445

DOI: 10.1021/acs.jnatprod.6b00170 J. Nat. Prod. 2016, 79, 2439−2445