Two flavonoid glycosides from Chenopodium murale

Phytochemistry 53 (2000) 299±303 www.elsevier.com/locate/phytochem Two ¯avonoid glycosides from Chenopodium murale Ahmed A. Gohar a,*, Galal T. Maatooq a, Masatake Niwa b a Department of Pharmacognosy, Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt Department of Medicinal Resources Chemistry, Faculty of Pharmacy, Meijo University, Tempaku, Nagoya 4688503, Japan b Received 23 June 1999; accepted 23 June 1999 Abstract Two new triglycosides, kaempferol-3-O-{(4-b-D-apiofuranosyl)-a-L-rhamnopyranoside}-7-O-a-L-rhamnopyranoside and kaempferol-3-O-{(4-b-D-xylopyranosyl)-a-L-rhamnopyranoside}-7-O-a-L-rhamnopyranoside were isolated from the methanol extract of Chenopodium murale, together with a known diglycoside, kaempferol-3-O-b-D-glucopyranoside-7-O-a-Lrhamnopyranoside. The characterization of the three compounds was achieved by various spectroscopic methods. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Chenopodium murale; Chenopodiaceae; Flavonoids; Flavonols; Kaempferol; Glycosides 1. Introduction In the previous paper, the presence of ¯avonoids having dose-related hypotensive activity was reported in Chenopodium murale L. (Gohar & Elmazar, 1997). TLC and gravity column chromatography of the BuOH fraction a€orded three ¯avonoids, one of them was identi®ed as kaempferol-3,7-dirhamnoside. The identity of the other two compounds was not veri®ed (Gohar & Elmazar, 1997). In this report, a full analysis of these ¯avonoids is presented. 2. Results and discussion TLC and gravity column chromatography of the BuOH fraction of the methanolic extract of Chenopodium murale L. a€orded three ¯avonoids. Kaempferol-3,7-dirhamnoside 1 in addition to compounds 2 and 3 were obtained (Gohar & Elmazar, 1997). Compound 2 was proved to be a mixture by NMR experiments. The TLC of 2 using chromatographic system A (Gohar & Elmazar, 1997), double development, resulted in resolution of 2 into two com- * Corresponding author. pounds (Rf 0.53 and 0.51). RpC18 Ð TLC of 2 using 40% aqueous methanol resolved it into two components which were isolated by preparative reversed phase HPLC using 45% aqueous methanol as mobile phase by isocratic elution (Carotenuto, Fattorusso, Lanzotti, Magno, de Feo, Cicala, 1997). The resolved compounds were noted as 2A (Rt 2.82; TLC, system A, Rf 0.53, double run) and 2B (Rt 7.55, TLC system A, Rf 0.51 double run). Compound 2A was identi®ed as kaempferol-3-O-b-D-glucopyranoside-7-O-a-L-rhamnoside. Its identity was veri®ed by comparison of its spectral data with those reported in the literature (Markham & Mahan Chari, 1982; Kowalewski & Wierzbicka, 1971; Mabry, Markham & Thomas, 1970; Gieger & Schwinger, 1980; Markham, Ternai, Stanley, Geiger & Mabry, 1978). The IR spectrum of compound 2B showed strong absorption bands at 3420 (OH), 1610 (C.O), 2950 (C± H), 1650 (C.C, aromatic), and broad band at 1130± 1000 cmÿ1 indicating its glycosidic nature (Jain, Sarwar-Alam, Kamil, Ilyas, Niwa & Sakae, 1990). Its reaction (¯uorescent yellow in UV with AlCl3) and UV spectral data with diagnostic shift reagents (Mabry et al., 1970; Markham & Mabry, 1975) suggested the likely presence of 3,7-disubstituted ¯avonol glycoside with free hydroxyl groups at 5 and 4 '-positions. Two intermediate spots were detected upon mild acid hy- 0031-9422/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 3 1 - 9 4 2 2 ( 9 9 ) 0 0 5 2 5 - 7 300 A.A. Gohar et al. / Phytochemistry 53 (2000) 299±303 Table 1 1 H-NMR data and HMBC results of compounds 3, 2A and 2Ba No. 3 1 6 8 2' 3' 5' 6' Rha-3 10 20 30 40 50 60 Rha-7 11 21 31 41 51 61 Xylose 12 22 32 42 52 glc. 3 10 2 30 40 50 6 Apiose 12 22 42 52 2A H-NMR = = = = = 2.4 2.4 9 8 8 HMBC correlations 1 95.87, 107.49 100.55, 107.49 6037 s 6.73 s 8.03 d, J = 9.5 6.76 d, J = 8.8 6.76 d, J = 8.8 6.41 6.67 7.75 6.92 6.92 d, d, d, d, d, 5.45 4.21 3.82 3.35 3.68 1.05 d, J = 1.2 m d, J = 3.3 m m d, J = 6.6 136.97, 82.6 5.55 4.00 3.84 3.84 3.60 1.25 d, J = 1.2 m d, J = 3.3 t m d, J = 6.5 163.43 4.30 3.20 3.30 3.45 3.08 d, J = 8.6 m m m m 82.6 J J J J J 2B 122.24 122.24 H-NMR HMBC correlations 1 HMBC correlations H-NMR 6.37 6.69 7.69 6.73 6.73 7.69 s s d, d, d, d, J J J J = = = = 8.8 8.8 8.8 8.8 5.22 s 3.42 m 3.82 m 3.28 m 3.76 m 0.8 d, J = 4.4 82.6 5.51 3.40 3.62 3.32 3.08 1.10 d, J = 1.2 m m m m d, J = 6.58 69.01, 76.95 5.50 s 3.25±3.8 m 3.25±3.8 m 3.25±3.8 m 3.25±3.8 m 1.1 d, J = 5.66 5.42 d, J = 7.33 3.18 m 3.20 m 3.08 br 3.82 br b-3.32 br, a-3.54 br 5.15 3.94 3.53 3.33 d, J = 2.2 br.s m, 3.75 d, J = 9.6 d, J = 4.4 3.29, br.m 73.55, 76.95 a The solvent is DMSO-d6 for 2A and 2B and CD3OD for 3. The chemical shifts are expressed in (ppm) and the coupling constant (J ) is expressed in Hz/s. The multiplicities are represented by s for singlet, d for doublet, t for triplet, m for multiplet and br for broad. drolysis of 2B with 1 N HCl, before yielding the aglycone. This suggested the presence of three sugar moieties. Two sugars were detected and proved to be rhamnose and apiose by comparing their paper chromatography and GC of their TMS derivatives with the natural authentic samples. GC indicated that the ratio of rhamnose to apiose was 2 : 1. NMR of 2B further con®rmed the presence of two rhamnose (signals at d 0.8 and d 1.1 in 1 H-NMR and at d 17.82 and d 18.11 in 13 C-NMR for the two methyl groups) and one apiose residue. The carbon signal at d 109.20 as well as the CH2 signal (DEPT) resonated at d 73.55 were assigned to the anomeric and C42 of the apiose moiety, respectively, (Tables 1 and 2). The rest of the sugar carbons were assigned by comparison with the published data (Markham & Mahan Chari, 1982; Markham et al., 1978). The aglycone was proved to be kaempferol by direct co-chromatography with authentic sample, UV and 1 H-NMR. The mass spectrum (FAB+) of 2B showed the presence of fragments having m/z 733 calculated for M + Na, 711 for M + 1 corresponding to molecular formula C32H38O18, 565 for (M + 1)-rha, 433 for (M + 1)-rha-api, and 287 for the aglycone M + 1. This is consistent with the presence of two rhamnose, one apiose and one kaempferol unit. The fragmentation sequence proved that one rhamnose and the apiose fragment must be terminal sugars (Crow, Tomer, Looker & Gross, 1986). 301 A.A. Gohar et al. / Phytochemistry 53 (2000) 299±303 The 1 H-, 13 C-NMR and DEPT spectra (Tables 1 and 2) con®rmed this structural hypothesis. The anomeric carbon atoms of the two rhamnose units resonate at d 101.56 and d 98.47. The chemically shifted signal at d 101.56 was assigned to the rhamnose unit linked at C3, while the signal at d 98.47 was assigned to the rhamnose at C7 of the aglycone (Agrawal & Bansal, 1989). An HMBC experiment (Table 1) revealed a correlation between the signal at d 76.95 assigned to C40 of the rhamnose at C3 of the aglycone and the anomeric proton of apiose resonated at d 5.15 as well as to the signal at d 0.8 assigned to protons of the methyl group of the rhamnose residue. The latter was assigned to H6 of rhamnose at position 3 of the aglycone (Chang, 1978). This suggests that apiose residue is attached to C40 of the rhamnose moiety at position 3 of the aglycone. This was con®rmed from the low-®eld shift of C40 at d 76.95 and from the high-®eld shift of H40 at d 3.28 (Agrawal & Bansal, 1989; Carotenuto, de Feo, Fattorosso, Lanzotti, Magno & Cicala, 1996; Kikuchi & Matsuda, 1996). Di€erent protons of the sugar residues were assigned using the anomeric protons as starting points in the 1 H-NMR spectrum for analysis of the HHCOSY and CHSHF spectra. From these data, 2B was identi®ed as kaempferol-3-O-[4-b-D-apiofuranosyl]-a-L-rhamnopyranoside-7-O-a-L-rhamnopyranoside which has been not reported before. The striking similarity of IR, UV and MS FAB+ between 2B and 3 suggested a close similarity in their structure. The UV spectrum and its changes in the presence of diagnostic shift reagents (Mabry et al., 1970; Markham & Mabry, 1975) pointed to the presence of free hydroxyl groups at C5 and C4 ' of a 3,7-disubstituted ¯avonoid glycoside framework. Acid hydrolysis of 3 gave the same result as 2B except for the presence of xylose sugar instead of apiose. The MS FAB+ of 3 is in agreement with the suggested structure. Fragment m/z 711 (M + 1) calculated for C32H38O18, m/z 565 (loss of one rhamnose), m/z 578 (loss of xylose) and m/z 287 accounted for M + 1 of the aglycone. The NMR spectra of 3 (Tables 1 and 2) con®rmed the previous conclusions. The chemical shift of the two anomeric carbon atoms of rhamnose residues unambiguously con®rmed their linkage to C3 and C7 of the kaempferol residue (Agrawal & Bansal, 1989). As mentioned for 2B, the xylose was deduced to be linked to C40; rhamnose linked to C3 of kaempferol (Agrawal & Bansal, 1989; Carotenuto et al., 1996). The previous conclusion was con®rmed from the HMBC experiment since the proton signals at d 6.41 and d 6.67 (assigned to 6 and 8 positions, respectively) are correlated with the carbon resonances at d 107.49, d 95.87) and d 107.49, d 100.55) assigned to (C10, C8) and (C10, C6), respectively. Also, protons at 3 ' and 5 ' d 6.92) were found to interact with C1 ' d 122.24). The location of Table 2 13 C-NMR of compounds 3, 2A and 2Ba Carbon 3 2 3 4 5 6 7 8 9 10 1' 2' 3' 4' 5' 6' Rha-3 10 20 30 40 50 60 Rha-7 11 21 31 41 51 61 Xylose 12 22 32 42 52 glc. 3 10 20 30 40 50 60 Apiose 12 22 32 42 52 157.95 136.97 179.74 162.93 100.55 163.43 95.87 159.59 107.49 122.24 131.94 116.60 161.73 116.60 131.94 (s ) (s ) (s ) (s ) (d ) (s ) (d ) (s ) (s ) (s ) (d ) (d ) (s ) (d ) (d ) 103.09 73.57 71.87 82.60 71.83 17.68 (d ) (d ) (d ) (d ) (d ) (q ) 99.78 72.03 71.67 73.57 71.24 18.09 (d ) (d ) (d ) (d ) (d ) (q ) 107.67 75.20 77.73 70.93 67.06 (d ) (d ) (d ) (d ) (t ) 2A 2B 155.93 133.16 177.32 161.57 99.62 161.57 96.6 156.79 105.95 118.71 131.24 116.16 157.30 116.60 131.24 156.27 133.70 177.52 161.60 99.66 161.6 95.2 156.27 106.16 123.41 130.83 117.00 159.33 117.00 130.24 101.56 70.70 70.41 76.95 69.01 17.82 98.45 70.19 70.09 71.82 70.04 18.09 98.47 70.52 70.23 71.82 70.01 18.11 101.12 74.40 77.65 70.01 76.63 61.03 109.20 76.24 79.22 73.55 63.60 (d ) (d ) (s ) (t ) (t ) a The solvent is DMSO-d6 for 2A and 2B and CD3OD for 3. The chemical shifts are expressed in (ppm). The multiplicities are represented by s for singlet, d for doublet, t for triplet and q for quartet. the rhamnose units at positions 3 and 7, with anomeric carbons resonating at d 103.09 and 99.78, respectively, was con®rmed from HMBC correlation between their respective anomeric protons and target carbon atoms. The anomeric proton at d 5.45 (rha-3) was correlated with C3 d 136.97) and the proton at d 5.55 (rha-7) was correlated with C7 d 163.43). These results con- 302 A.A. Gohar et al. / Phytochemistry 53 (2000) 299±303 ®rm the previous assignment based on the conclusion of Agrawal and Bansal (1989). The xylose moiety was deduced to be attached to C40 of the rhamnose at position-3 from HMBC correlation of its anomeric proton d 4.3) with the rhamnose C40 d 82.6) which, in turn, was correlated with the 6-methyl protons of rhamnose at position-3. From these data, 3 was identi®ed as kaempferol-3-O-(4-b-D-xylopyranosyl)-a-L-rhamnopyranoside-7-O-a-L-rhamnopyranoside. From the chemotaxonomic point of view, the genus Chenopodium contains both ¯avones and ¯avonols. Flavones are reported in C. graveolens (Mata, Navarrete, Alvarez, Pereda-Miranda, Delgado & Romo de Vivar, 1987), methoxylated ¯avones in C. botrys (de Pascual-T, Gonzalez, Vicente & Bellido, 1981), 3-O-substituted ¯avonol glycosides in C. quinoa and C. ambrosioides (Jain et al., 1990; de Simone, Dini, Pizza, Saturnino & Schettino, 1990). Concerning C. murale, this is the ®rst report for all the discussed compounds. The presence of apiose in C. murale supports the previous reports of its presence in C.quinoa (de Simone et al., 1990) as well as in another genus in the family Chenopodiaceae; Spinacia (Aritomi, Komori & Kawasaki, 1986; Williams & Harborne, 1994). spectra in KBr discs. NMR spectra were run at 600 MHz 1 H† and 150 MHz 13 C† in DMSO-d6 (compound 2A and 2B) or in CD3OD (compound 3) using TMS as internal standard. MS were obtained by FAB+ at 70 eV. TLC was performed using silica gel GF254 (Merck), EtOAc±MeOH±H2O (100 : 15 : 10) mixture was used as solvent (A). Whatmann No. 1 paper was used in PC, 15% AcOH and EtOAc± Pyridine±H2O (5 : 5 : 4) mixtures were used as solvents (B and C, respectively). AlCl3 (+UV 366 nm) and aniline hydrogen phthalate spray reagents were used for detection. Plant materials, extraction, chromatography, and preparation of fraction II (Gohar & Elmazar, 1997) Fraction II was subjected to repeated column chromatography (250 silica gel). Elution was done using EtOAc±MeOH±H2O (100 : 10 : 5) mixture, 100 ml fractions were collected. Two groups of the resolved compounds were separately collected. From the ®rst group (900 ml), compound 1 was recovered (Gohar & Elmazar, 1997). The second group, following 1200 ml gave a residue (4.8 g) which was subjected to repeated column chromatography, using the same condition. From the ®rst 1200 ml eluate, compound 2 was obtained (2.8 g). From the next 800 ml eluate, compound 3 was recovered by repeated recrystallization from MeOH (255 mg). RpC18 Ð TLC of 2 using 40% MeOH followed preparative reversed phase HPLC using 45% aqueous MeOH resulted in resolution of 2 into 2A (137 mg) and 2B (157 mg); Waters 600E-Millipore 6plepf504 attached to waters 486 Tunable Absorbence detector, column 7.8  300 mm, C18 prep., lmax 345 nm, aufs 0.05, att., variable 512±1024, ¯ow rate 4 ml/min, chart speed 0.25 cm/min. 3.2. Kaempferol-3-O-b-D-glucopyranoside-7-O-a-Lrhamnopyranoside 2A Pale yellow crystals, mp 2548C; ‰aŠ25 D ˆ ÿ748 (MeOH: c 0.25); FAB-MS (positive ion) m/z 595 M + 1; 617, M + Na; 433, (M + 1)-gluc; UV spectra, lmax nm MeOH 210, 266, 347; + NaOMe 212, 266, 396; + AlCl3 212, 274, 301sh, 350, 397; + AlCl3±HCl 212, 274, 301sh, 349, 397; + NaOAc 213, 266, 352; + NaOAc±H3BO3 213, 266, 352; IR. 3420 (OH), 2950 (C±H), 1650 (C.C aromatic), 1610 (C.O), 1130±1000 cmÿ1 (glycosidic linkage); NMR data (Tables 1 and 2). 3.3. Acid hydrolysis 3. Experimental 3.1. General Mps uncorr., UV spectra were run in MeOH and IR An alcoholic solution (20 mg) was re¯uxed on boiling water bath with 1 N HCl. The solution was monitored by PC System B, time interval 5 min, for 1 h. The excess acid was precipitated with Ag2O, the alcohol evaporated and the aglycone extracted with EtOAc A.A. Gohar et al. / Phytochemistry 53 (2000) 299±303 and recrystallized from methanol. The sugars in the aqueous solution were examined by PC (System C) and by GLC, and the aglycone was subjected to UV and 1 H-NMR analysis. 3.4. GLC analysis of sugars The neutral aqueous hydrolysates were silylated with BSFTA/TMS for 15 min at room temperature in pyridine. Silylated samples were subjected to GLC analysis: column BP5-25 m, 0.25 mm id; column temperature 200±3008C; 58C/min; 20 min; dect, temperature 3008C (Fid); helium. 3.5. Identi®cation of aglycone (kaempferol) Yellow needles, mp 2808C, UV lmax nm: MeOH 265, 371; + NaOMe 263, 285, 359sh, 451; + AlCl3 261, 300sh, 364, 426; + AlCl3±HCl 261, 300sh, 346sh, 427; + NaOAc 262, 322sh, 384; + NaOAc±H3BO3 257, 314sh, 369. 1 H-NMR d 8.07, d, J = 8.69 Hz (H2 ',6 '); d 6.89, d, J = 8.79 Hz (H3 ',5 '); d 6.39, d, J = 1.46 Hz (H8); d 6.17, d, J = 2.19 Hz (H6). 3.6. Kaempferol-3-O-[4-b-D-apiofuranosyl]-a-L-rhamnopyranoside-7-O-a-L-rhamnopyranoside 2B Yellow crystals, mp 2248C; ‰aŠ25 D ˆ ÿ1818 (MeOH: c 0.15), FAB-MS (positive ion) m/z 733 (13.5) M + Na, 711 (10.18) M + 1, 565 (1), (M + 1)-rha, 433 (M + 1)-rha-api, 287 (2.5) M + 1 for aglycone; UV spectra lmax nm: MeOH 210, 265, 343; + NaOMe 211, 265, 387 + AlCl3 212, 268, 398; + AlCl3±HCl 210, 267, 343sh, 397; + NaOAc 210, 265, 343; + NaOAc± H3BO3 212, 265, 344; IR 3420 (OH), 2950 (C±H), 1650 (C.C), 1610 (C.0), 1130±1000 cmÿ1 (glycosidic linkage); NMR data (Tables 1 and 2). Acid hydrolysis and identi®cation of sugars and aglycone as compound 2A. 3.7. Kaempferol-3-O-(4-b-D-xylopyranosyl)-a-Lrhamnopyranoside-7-O-a-L-rhamnoside 3 Pale yellow crystals, mp 2328C; ‰aŠ25 D ˆ ÿ1548 (MeOH: c 0.114); FAB-MS (positive ion) m/z 711 (2.5) M + 1, 578 (10) (M + 1)-xyl, 565 (6.5) (M + 1)-rha, 303 287 M + 1 for aglycone; UV spectra lmax nm MeOH 209, 265, 326+; + NaOMe 210, 247, 390; + AlCl3 210, 247, 301sh, 349, 398; + AlCl3±HCl 210, 275, 301sh, 344, 397; + NaOAc 214, 248, 350; + NaOAc± H3BO3 212, 247, 344; IR. 3420 (OH), 2950 (C±H), 1650 (C.C), 1610 (C.O), 1130±1100 cmÿ1 (glycosidic linkage); NMR experiments (Tables 1 and 2). Acid hydrolysis and identi®cation of sugars and aglycone as compound 2A. References Agrawal, P. K., & Bansal, M. C. (1989). Flavonoid glycosides. In P. K. Agrawal, Carbon-13 NMR of ¯avonoids (p. 283). Amesterdam: Elsevier. Aritomi, M., Komori, T., & Kawasaki, T. (1986). Phytochemistry, 25, 231. Carotenuto, A., de Feo, V., Fattorusso, E., Lanzotti, V., Magno, S., & Cicala, C. (1996). Phytochemistry, 41, 531. 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