Coumarins and xanthones from the seeds of Mammea siamensis

J. Braz. Chem. Soc., Vol. 18, No. 5, 1077-1080, 2007. Printed in Brazil - ©2007 Sociedade Brasileira de Química 0103 - 5053 $6.00+0.00 ,a a a Surat Laphookhieo,* Phunrawie Promnart, John Keith Syers, Akkharawit Kanjana-Opas, c c Chanita Ponglimanont and Chatchanok Karalai b a School of Science, Mae Fah Luang University, Tasud, Muang, Chiang Rai 57100, Thailand b Department of Industrial Biotechnology, Faculty of Agro-Industry, Prince of Songkla University, Hat-Yai, Songkhla 90112, Thailand c Department of Chemistry, Faculty of Science, Prince of Songkla University, Hat-Yai, Songkhla 90112, Thailand Uma cumarina inédita, mammea E/BB ciclo D (1), juntamente com cinco compostos conhecidos, mammea E/BA ciclo D (2), suragina C (3), terapina B (4), 1,7-dihidroxixantona (5) e 1-hidróxi-5-metoxyxantona (6), foram isolados de sementes de Mammea siamensis. Suas estruturas foram caracterizadas usando dados de RMN 1D e 2D. Suragina C e terapina B mostraram atividade citotóxica contra adenocarcinoma de mama (MCF-7), câncer cervical humano (HeLa), câncer de colon (HT-29) e câncer oral humano (KB). A new coumarin, mammea E/BB cyclo D (1), together with five known compounds, mammea E/BA cyclo D (2), suragin C (3), therapin B (4), 1,7-dihydroxyxanthone (5) and 1-hydroxy-5methoxyxanthone (6), were isolated from the seeds of Mammea siamensis. Their structures were characterized using 1D and 2D NMR spectral data. Suragin C and therapin B showed cytotoxic activity against breast adenocarcinoma (MCF-7), human cervical cancer (HeLa), colon cancer (HT-29) and human oral cancer (KB). Keywords: mammea E/BB cyclo D, cytotoxic activity, Mammea siamensis, guttiferrae Introduction Experimental Mammea siamensis (Miq) T. Anders. (Guttiferae), known in Thai as “Sarapi”, is a small evergreen tree distributed in Thailand, Laos, Cambodia, Vietnam and Myanmar. The flowers of this plant have been used in traditional Thai medicine as a heart tonic. Investigations of different parts of the plant have revealed the presence of several coumarins and xanthones.1-4 We have previously reported the isolation and structure determination of phenolic compounds from the seeds of this species.5 In a continuation of our study on this plant, we now report herein the isolation and structure elucidation of a novel compound, mammea E/BB cyclo D (1), together with three known coumarins, mammea E/BC cyclo D (2),3 suragin C (3),6 therapin B (4)7 and two known xanthones, 1,7-dihydroxyxanthone (5)8 and 1-hydroxy-5methoxyxanthone (6)9 from the CH2Cl2 extract (Figure 1). The cytotoxic activity of all isolates is also reported. General procedures *e-mail: ; Melting points were determined using a Fisher-John melting point apparatus. The optical rotation [α]D values were determined with a JASCO P-1020 polarimeter. UV spectra were measured with a UV-160A spectrophotometer (Shimadzu). The IR spectra were measured with a PerkinElmer FTS FT-IR spectrophotometer. The 1H and 13C NMR spectra were recorded using 500 MHz Varian UNITY INOVA and 300 MHz Bruker FTNMR Ultra ShieldTM spectrometers. Chemical shifts were recorded in parts per million (δ) in CDCl3 with tetramethylsilane (TMS) as an internal reference. The EIMS was obtained from a MAT 95 XL mass spectrometer. Quick column chromatography (QCC) and column chromatography (CC) were carried out on silica gel 60 F254 (Merck, 230-400 Mesh ASTM) and silica gel 100 (Merck, 70-230 Mesh ASTM), respectively. Precoated plates of silica gel 60 F254 and reversed-phase (RP-18 F254S) were used for analytical purposes. Short Report Coumarins and Xanthones from the Seeds of Mammea siamensis 1078 Coumarins and Xanthones from the Seeds of Mammea siamensis 8'' 7'' 3' 2' 6'' 4'' 1' 3 4a 8a 8 1 O 1''' O 2''' R 2 R O O R 6 HO O 3 4a 8a 8 3' 1' O R2 O O R 3''' 10'' 4''' R2 = CH3 3: R = 4: R = 5'' 3'' 1 9'' 1'' 2'' OH O 1 1 1: R1 = CH3; R2 = H 2: R1 = H; 2' HO OH O O 1'' 6 HO J. Braz. Chem. Soc. 4'' 6'' 7'' 8'' 5: R1 = H; R2 = OH 6: R1 = OMe; R2 = H Figure 1. Structures of compounds 1-6. Plant material The seeds of M. siamensis were collected from Mae Fah Luang University, Tasud, Muang, Chiang Rai Province, northern Thailand in August 2005. The identification was made by Professor Puangpen Sirirugsa, Department of Biology, Faculty of Science, Prince of Songkla University and a voucher specimen (No. SC09) was deposited at Prince of Songkla University Herbarium. Extraction and Isolation The seeds (224.5 g) of M. siamensis were extracted successively with CH2Cl2 (500 mL) at room temperature for 5 days. The filtered samples were combined and the solvents were evaporated under reduced pressure to provide the CH2Cl2 extracts (44.4 g). The CH2Cl2 extract (44.4 g) was chromatographed by QCC and eluted with hexane-EtOAc mixtures to give seven fractions (F1-F7). Fraction F2 (1.92 g) was purified by RP18 CC with acetone: H2O (3:1) and followed by RP-18 preparative TLC with acetone: H2O (3:1) to yield 1 (3.1 mg) and 2 (4.3 mg). Fraction F4 (3.35 g) was separated by CC with EtOAc: hexane (3:17) and followed by RP-18 preparative TLC with MeOH:H2O (4:1) to provide five subfractions (F4a-F4e). Subfraction F4b (12.8 mg) was purified by preparative TLC with EtOAc: hexane (1:3, v/ v) to give 5 (2.1 mg). Subfraction F4d (1.02 g) was purified by RP-18 CC with MeOH:H2O (4:1) and followed by CC with EtOAc: hexane (1:3) to afford 4 (16.8 mg) and 3 (32.6 mg). Fraction F6 (167.0 mg) was separated by CC with EtOAc: hexane (2:3, v/v) to give 6 (6.3 mg). Mammea E/BB cyclo D (1) Yellowish viscous oil; 1H NMR (δ, CDCl3, 300 MHz): 14.44 (7-OH), 6.74 (1H, d, J 10.0 Hz, H-4′′), 6.60 (1H, dd, J 6.8, 2.8 Hz, H-1′), 6.30 (1H, s, H-3), 5.60 (1H, d, J 10.0 Hz, H-5′′), 4.02 (1H, sextet, J 6.3 Hz, H-2′′′), 2.17 (3H, s, H-1′-COCH3), 1.97 (1H, m, H-2′a), 1.80 (1H, m, H-3′′′a), 1.78 (1H, m, H-2′b), 1.58 (3H, s, H-7′′), 1.56 (3H, s, H-8′), 1.45 (1H, m, H-3′′′b), 1.26 (3H, d, J 6.3 Hz, H-5′′′), 1.07 (3H, t, J 7.2 Hz, H-3′) and 1.06 (3H, t, J 7.2 Hz, H-4′′′); 13C NMR data (CDCl3, 75 MHz): 210.8 (C1′′′), 170.3 (CH3CO), 163.5 (C-7), 159.3 (C-2), 157.5 (C4), 156.7 (C-8a), 155.7 (C-5), 126.8 (C-5′′), 115.8 (C4′′), 106.5 (C-6), 106.4 (C-3), 103.7 (C-8), 100.9 (C-4a), 80.2 (C-6′′), 73.0 (C-1′), 46.9 (C-2′′′), 29.6 (C-3′′′), 28.6 (C-2′), 28.4 (C-7′′), 27.8 (C-8′′), 21.0 (CH3CO), 16.9 (C5′′′), 10.6 (C-4′′′), 10.0 (C-3′); EIMS m/z (rel. int.): 428 [M]+ (39), 413 (100), 371 (45), 353 (13), 311 (29), 283 (5); HREIMS m/z [M]+ 428.1813 (calc. for C24H28O7, 428.1835); UV(MeOH) λmax/nm: 225, 280, 285, 300, 373; IR(CHCl3) νmax/cm-1: 3454, 1738, 1655, 1605; [α]D27-15.0° (c 0.10, MeOH). Cytotoxicity assay The procedure for cytotoxic assay was performed by sulphorhodamine B (SRB) assay as described by Skehan et al.10 In this study, four cancer cell lines, MCF-7 (breast adenocarcinoma), HeLa (human cervical cancer), HT-29 (colon cancer) and KB (human oral cancer) were used. Camptothecin, the refer (...truncated)