Flavonoids and phenolics from the wholeplant of Macrosolen bidoupensis Tangane & V.S. Dang

Cite this paper: Vietnam J. Chem., 2021, 59(1), 115-119 Article DOI: 10.1002/vjch.202000138 115 Wiley Online Library © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH Flavonoids and phenolics from the wholeplant of Macrosolen bidoupensis Tangane & V.S. Dang Le Kieu Hung1,3, Phan Duy Thanh4,5, Phan Nhat Minh2, Bui Trong Dat2, Pham Nguyen Kim Tuyen4, Huynh Bui Linh Chi6, Nguyen Thi Ngoc Dan7, Dang Van Son8, Mai Dinh Tri1,2, Nguyen Tan Phat1,2* 1Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi 10000, Viet Nam 2Institute of Chemical Technology, Vietnam Academy of Science and Technology, Thanh Loc 29, Thanh Loc, District 12, Ho Chi Minh City 70000, Viet Nam 3Le Quy Don High School, 3/2 Street, Vung Tau City, Ba Ria-Vung Tau Province 78000, Viet Nam 4Sai Gon University, 273 An Duong Vuong, Ho Chi Minh City 70000, Viet Nam 5Le Thi Hong Gam Career Orientation and General Technical Education Centre, 147 Pasteur, Ho Chi Minh City 70000, Viet Nam 6Department of Science, Dong Nai University, 04 Le Quy Don, Bien Hoa City, Dong Nai Province 76000, Viet Nam 7Research Center of Ginseng and Medicinal Materials Ho Chi Minh City, Vietnam National Institute of Medicinal Materials, 41 Dinh Tien Hoang, District 1, Ho Chi Minh City 70000, Viet Nam 8Institute of Tropical Biology, Vietnam Academy of Science and Technology, 85 Tran Quoc Toan, District 3, Ho Chi Minh City 70000, Viet Nam Submitted August 11, 2020; Accepted September 16, 2020 Abstract Five flavonoids, including quercetin (1) and four its derivatives, quercitrin (2), isoquercitrin (3), astibin (4), and rutin (5), together with two phenolic glycosides, 3,3′-di-O-methylellagic acid 4-O-β-D-xylopyranoside (6), and aesculin (7) were isolated from the whole plants of Macrosolen bidoupensis Tangane & V.S. Dang. Their chemical structures were characterized using HR-ESI-MS, NMR data and comparison with published data. Compounds (3, 4 & 7) were notified from the Macrosolen genus for the first time, whereas, all isolated compounds were informed for the first time from this species. Keywords. Macrosolen bidoupensis, Loranthaceae, quercetin derivatives, astibin, aesculin. 1. INTRODUCTION The Macrosolen genus (Loranthaceae), a small parasitic shrub, comprising about forty species are widely distributed in tropical South and Southeast Asia.[1,2] Seven species were recorded in Viet Nam.[2,3] Macrosolen bidoupensis, a new species was discovered in Bidoup, Nui Ba National Park, Lam Dong Province, Vietnam in 2017.[2] In our earlier research, four triterpenoids, 3-oxofriedelane (1), 3-hydroxyfriedelane (2), 3- hydroxyfriedelane-28-oic acid (3), and 3- hydroxyglutin-5-ene (4) were verified from this species.[4] Hence, this paper detailed the separation and structural elucidation of five flavonoids (1-5) and two phenolics (6 and 7) from the whole plant of Macrosolen bidoupensis were collected in Bidoup Nui Ba National Park, Lam Dong Province, Vietnam. 2. MATERIALS AND METHODS 2.1. Methods The high resolution electrospray ionization mass spectroscopy (HR-ESI-MS) measurement was performed on a UPLC-MSQ Plus spectrometer (Thermo, USA). The 1H-NMR (500 MHz), 13C- Vietnam Journal of Chemistry Nguyen Tan Phat et al. © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH www.vjc.wiley-vch.de 116 NMR (125 MHz), HSQC, HMBC spectra of the studied compounds were recorded by mean of Bruker AM500 FT-NMR spectrometer. Column chromatography was carried out by normal-phase silica gel (230-400 mesh). Analytical TLC was carried out on silica gel plates (Kieselgel 60 F254, Merck). 2.2. Plant material The Macrosolen bidoupensis whole plants were collected in Bidoup Nui Ba National Park, Lam Dong Province (Dec 2018) and recognized by Dr. V. S. Dang, Institute of Tropical Biology. A voucher specimen (No.VH/PHAT-MB1218) was deposited in Bioactive Compounds Laboratory, Institute of Chemical Technology. 2.3. Extraction and isolation The 8 kg dried powder of M. bidoupensis were macerated with ethanol 96o for three times (330 L) at the room temperature to yield the crude extract. It (1000 g) was objected to liquid phase extraction and segregated into n-hexane, ethyl acetate and aqueous portion. The aqueous one was fractioned using Dianion HP-20 column with H2O-MeOH solvents (100-0, 75-25, 50-50, 25-75, 0-100, v/v) to collect five fractions (I-V), respectively. Fraction IV (205 g) was applied to silica gel chromatographical column using eluted solvents of EtOAc-MeOH gradient (from 0 % to 100 %) to provide seven subfractions (IV.1-IV.7). Subfraction IV.2 (8 g) was eluted on silica gel column with solvent systems CHCl3- MeOH (98:2  85:15, v/v) to obtain 1 (5 mg), and 6 (8 mg). Subfraction IV.3 (21 g) was separated on silica gel column chromatography with solvents CHCl3-MeOH (90:10  80:20, v/v), and purified on reversed phase RP-18 chromatography by mixtures of H2O-MeOH (60-40, v/v) to afford 2 (5 mg) and 4 (4 mg). Subfraction IV.4 (25 g) was re- chromatographed with CHCl3-MeOH-H2O as an eluting solvent (85:15:0  75:25:2, v/v) to get 3 (5 mg), 7 (4 mg), and 5 (6 mg). The NMR data for isolated compounds (1-5), see table 1. 3,3′-di-O-methylellagic acid 4-O-β-D- xylopyranoside (6): 1H-NMR (500 MHz, DMSO- d6,  ppm, J in Hz): 7.73 (1H, s, H-5), 7.50 (1H, s, H-5’), 5.16 (1H, d, 7.5, H-1’’), 3.83 (1H, dd, 11.0 & 5.0, H-5’’a), 3.32-3.44 (4H, m, H-2’’  H4’’, H- 5’’b), 4.08 (3H, s, 3-OCH3), 4.04 (3H, s, 3’-OCH3). 13C-NMR (125 MHz, DMSO-d6,  ppm): 114.2 (C- 1), 111.1 (C-1’), 141.6 (C-2), 140.9 (C-2’), 141.9 (C-3), 140.2 (C-3’), 151.2 (C-4), 152.8 (C-4’), 111.8 (C-5), 111.6 (C-5’), 112.9 (C-6), 112.8 (C-6’), 158.4 (C-7), 158.3 (C-7’), 61.6 (3-OCH3), 61.0 (3’-OCH3), 101.9 (C-1’’), 73.0 (C-2’’), 76.1 (C-3’’), 69.3 (C- 4’’), 65.8 (C-5’’). Aesculin (7): 1H-NMR (500 MHz, DMSO-d6,  ppm, J in Hz): 6.24 (1H, d, 9.5, H-3), 7.86 (1H, d, 9.0, H-4), 7.46 (1H, s, H-5), 6.84 (1H, s, H-8), 4.86 (1H, d, 7.5, H-1’), 3.40-3.97 (6H, m, H-2’  H-6’). 13C-NMR (125 MHz, DMSO-d6,  ppm): 163.7 (C- 2), 113.1 (C-3), 146.0 (C-4), 116.7 (C-5), 144.5 (C- 6), 153.4 (C-7), 104.6 (C-8), 152.6 (C-9), 112.8 (C- 10), 104.3 (C-1’), 74.8 (C-2’), 78.5 (C-3’), 71.4 (C- 4’), 77.6 (C-5’), 62.5 (C-6’). 3. RESULTS AND DISCUSSION Compound 1 was given as a yellow amorphous powder. The molecular formula was established as C15H10O7 ([M-H]- m/z 301.0340, calcd. 301.0348). The 1H-NMR data of 1 (table 1) exhibited one intramolecular proton at δH 12.48 (1H, s, OH-5); three ABX aromatic protons at δH 7.67 (1H, d, J = 2.0 Hz, H-2’), 7.54 (1H, dd, J = 8.5 & 2.0 Hz, H-6’), and 6.88 (1H, d, J = 8.5 Hz, H-5’); two AX aromatic protons at δH 6.40 (1H, d, J = 2.5 Hz, H-8) and 6.18 (1H, d, J = 2.0 Hz, H-6) were identified as two 1,3,4-trisubstituted and 1,2,4,5-tetrasubstituted benzene rings, respectively. The 13C-NMR spectrum of 1 (table 1) showed fifteen carbons including one carbonyl carbon at δC 175.8 (C-4), seven oxygenated aromatic carbons, two quaternary aromatic carbons, and five sp2 methine carbons at δC 98.1 (C-6), 93.3 (C-8), 115.0 (C-2’), 115.6 (C-5’), and 119.9 (C-6’) were confirmed a flavonoid bearing five hydroxyl groups. Based on data of 1H, 13C-NMR and compared with those data; the structure of 1 was evidenced as 3,5,7,3’,4’-pentahydroxyflavone (quercetin).[5] Compound 2 was yield as a yellow amorphous powder. The molecular formula was demonstrated as C21H20O10 ([M-H]- m/z 447.0924, calcd. 447.0927; [2*M-H]- m/z 895.1936, calcd. 895.1933). The 13C & 1H-NMR data (table 1) displayed 2 has the same quercetin skeleton similar 1. Furthermore, the 13C- NMR data of 2 described one anomer carbon at δC 101.8 (C-1’’), four oxymethine carbons at 70.0-71.1 (C-2’’  C-5’’), and one methyl carbon at δC 17.4 (C-6’’) correlated with one anomer proton at δH 5.25 (1H, d, J = 1.0 Hz, H-1’’), four oxymethine protons at δH 3.15-3.98 (4H, H-2’’  H-5’’), and three methyl protons at δH 0.81 (3H, d, J = 6.0 Hz, H-6’’), respectively, in 1H-NMR, which were concentrated a O--L-rhamnopyranose unit (Rha). The HMBC Vietnam Journal of Chemistry Flavonoids and phenolics from © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH www.vjc.wiley-vch.de 117 spectrum showed the correlation between proton at δH 5.25 (H-1’’) and carbon at δC 134.2 (C-3) were determined a Rha moieties attached to be C-3 of aglycon. Thence, the structure of 2 was evinced as quercetin 3-O--L-rhamnopyranoside (quercitrin).[6] Compound 3 was given as a yellow amorphous powder. The molecular formula was identified as C21H20O12 ([M-H]- m/z 463.0878, calcd. 463.0877; [2*M-H]- m/z 927.1856, calcd. 927.1831). The 13C & 1H-NMR spectra of 3 (table 1) exhibited signals of a quercetin glycoside similar 2, except for the disappearing of one methyl carbon at δC 17.4 (C- 6’’)/δH 0.81 (H-6’’) in 2 and the appearing of one oxymethylene carbon at δC 60.9 (C-6’’)/δH 3.58 (1H, brd, J = 11.0 Hz, H-6’’a), 3.32 (1H, overlap, H- 6’’b); and the larger J coupling constant of proton H-1’ at δH 5.45 (1H, d, J = 7.0 Hz, H-1’’) in 3, which were signified a O-β-D-glycopyranose moieties (Glc). Furthermore, this proton at δH 5.45 (H-1’’) correlated with carbon at δC 133.3 (C-3) were indicated a Glc unit linked to be C-3 of a quercetin aglycon. Therefore, the structure of 3 was designated as quercetin 3-O-β-D-glycopyranoside (isoquercitrin).[6] Compound 4 was obtained as a white amorphous powder. The molecular formula was determined as C21H21O11 ([M-H]- m/z 449.1077, calcd. 449.1084; [2*M-H]- m/z 899.2231, calcd. 899.2246). The 13C and 1H-NMR spectra of 4 (table 1) showed twenty-one signals of flavonoid bearing one Rhamnose unit similar 2, except for the vanishing of two oxygenated aromatic carbons at δC 157.3 (C-2), 134.2 (C-3) in 2 and the arriving of two oxymethine carbons at δC 81.5 (C-2), 75.6 (C-3) in 3, which were proved the aglycon of 4 was to be 2,3- dihydroquercetin. Moreover, the configurations for C-2 and C-3 of 4 were distinguished to be 2R,3R by comparing the large coupling constants of two protons H-2 (δH 5.24) and H-3 (δH 4.65) in 4 (J = 10.0 Hz) with 2R,3S-dihydroquercetin (J = 2.4 Hz), whereas, the relative upfield of protons H-1’’, H-2’’ and downfield of protons H-5’’, H-6’’ in 4 with 2S,3S-dihydroquercetin. On the other hands, proton at δH 4.04 (H-1’’) correlated with carbon at δC 75.6 (C-3) in HMBC. So, the structure of 4 was indicated as 2R,3R- dihydroquercetin 3-O--L- rhamnopyranoside (astibin).[7] Compound 5 was afforded as a yellow amorphous powder. The molecular formula was designated as C27H30O16 ([M-H]- m/z 609.1451, calcd. 609.1456; [2*M-H]- m/z 1219.2994, calcd. 1219.2990). The 13C & 1H-NMR data of 5 (table 1) showed signals of a quercetin glucoside similar 3. Additionally, those of 5 revealed one O--L- rhamnopyranose unit (Rha) according one anomer carbon at δC 100.7 (C-1’’’)/δH 4.38 (1H, d, J = 1.0, H-1’’’), four oxygenated methine carbons at 68.2- 71.8 (C-2’’’C-5’’’), and one methyl carbon at δC 17.7 (C-6’’’)/δH 0.99 (3H, d, J = 6.0 Hz, H-6’’). On other hands, proton at δH 4.38 (H-1’’’) correlated with oxymethylene carbon at δC 66.9 (C-6’’). Hence, the structure of 5 was elucidated as quercetin 3-O- [-L-rhamnopyranosyl-(16)]-β-D- glucopyranoside (rutin).[5] Compound 6 was obtained as a white amorphous powder. The molecular formula was established as C21H18O12 by HR-ESI-MS data ([M- H]- m/z 461.0730, calcd. 461.0720). The 13C & 1H- NMR spectra of 6 displayed twenty-one carbons, comprising two -lactone carbonyl carbons at δC 158.4 (C-7), 158.3 (C-7’), six oxygenated aromatic carbons, four quaternary aromatic carbons, and two sp2 methine carbons at δC 111.8 (C-5), 111.6 (C-5’) corresponded with protons at δH 7.73 (1H, s, H-5), 7.50 (1H, s, H-5’), were identified an ellgalic acid framework. In addition, 6 has two methoxy groups at δC 61.6 (3-OCH3)/δH 4.08 (3H, s, 3-OCH3), 61.0 (3’-OCH3)/δH 4.04 (3H, s, 3’-OCH3), and one O-β- D-xylopyranose unit (Xyl) consenting one anomer carbon at δC 101.9 (C-1’’)/δH 5.16 (1H, d, J = 7.5 Hz, H-1’’), three oxymethine carbons at δC 73.0 (C- 2’’), 76.1 (C-3’’), 69.3 (C-4’’), and one oxymethylene carbon at δC 65.8 (C-5’’). The HMBC spectra exhibited the correlations between protons at δH 4.08 (3-OCH3), 4.04 (3’-OCH3), 5.14 (H-1’’) and carbons at δC 141.9 (C-3), 140.2 (C-3’), 151.2 (C-4), respectively, were illustrated two methoxy groups and Xyl unit linked to be C-3, C-3’, and C-4 of an ellgalic frame, respectively. So, the structure of 6 was designated as 3,3′-di-O-methylellagic acid 4- O-β-D-xylopyranoside.[8] Compound 7 was got as a white amorphous powder. The molecular formula was caculated as C15H16O9 ([M-H]- m/z 339.0716, calcd. 339.0716). The 13C and 1H-NMR spectrum of 7 exhibited fifteen carbons, including one carbonyl carbon at δC 163.7 (C-2), three oxygenated aromatic carbons, one quaternary aromatic carbon, four sp2 methine carbons at 113.1 (C-3), 146.0 (C-4), 116.7 (C-5), 104.6 (C-8) corresponded with protons at δH 6.24 (1H, d, 9.5, H-3), 7.86 (1H, d, 9.0, H-4), 7.46 (1H, s, H-5), 6.84 (1H, s, H-8), one anomer carbon at δC 104.3 (C-1’)/δH 4.86 (1H, d, 7.5, H-1’), four oxymethine carbons, and one oxymethylene carbon at δC 62.5 (C-6’), which were supported a 6,7- dihydroxycoumarin frame bearing one O-β-D- glycopyranose moieties (Glc). Based on data of 1H, 13C-NMR and the previous literature; the structure of 7 was proved as 6,7-dihydroxycoumarin 6-O--D- Vietnam Journal of Chemistry Nguyen Tan Phat et al. © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH www.vjc.wiley-vch.de 118 Table 1: 1H and 13C-NMR data of 1-5 in DMSO-d6 No. 13C NMR ( ppm) 1H NMR ( ppm, J in Hz) 1 2 3 4 5 1 2 3 4 5 2 146.8 157.3 156.3 81.5 156.5 5.24 (d, 10.0) 3 135.7 134.2 133.3 75.6 133.3 4.65 (d, 10.0) 4 175.8 177.7 177.4 194.5 177.3 5 160.7 161.3 161.2 163.4 161.2 6 98.1 98.6 98.6 96.0 98.6 6.18 (d, 2.0) 6.21 (d, 2.0) 6.20 (d, 2.0) 5.90 (d, 2.0) 6.19 (d, 2.0) 7 163.8 164.2 164.1 166.9 164.0 8 93.3 93.6 93.4 95.0 93.5 6.40 (d, 2.5) 6.39 (d, 2.0) 6.40 (d, 2.0) 5.88 (d, 2.0) 6.38 (d, 2.0) 9 156.1 156.4 156.3 162.1 156.4 10 103.0 104.0 103.9 101.0 103.9 1' 121.9 121.1 121.6 126.9 121.1 2' 115.0 115.6 115.2 114.7 115.2 7.67 (d, 2.0) 7.30 (d, 2.0) 7.57 (d, 2.0) 6.88 (brs) 7.53 (d, 1.5) 3' 145.0 145.2 144.8 145.9 144.7 4' 146.8 148.4 148.4 145.1 148.4 5' 115.6 115.4 116.2 115.3 116.2 6.88 (d, 8.5) 6.87 (d, 8.0) 6.84 (d, 9.0) 6.73 (brs) 6.84 (d, 8.0) 6' 119.9 120.7 121.1 118.9 121.5 7.54 (dd, 8.5 & 2.0) 7.25 (dd, 8.0 & 2.0) 7.58 (dd, 9.0 & 2.5) 6.73 (brs) 7.54 (dd, 10.0 & 2.0) 1'' 101.8 100.8 100.0 101.1 5.25 (d, 1.0) 5.45 (d, 7.0) 4.04 (brs) 5.34 (d, 7.5) 2'' 70.3 74.1 70.1 74.0 3.50 (brd, 9.0) 3.09-3.24 (m) 3.39-3.42 (m) 3.22-3.24 (m) 3'' 70.5 77.5 70.4 76.4 3.19-3.25 (m) 3.09-3.24 (m) 3.33-3.34 (m) 3.22-3.24 (m) 4'' 71.1 69.9 71.6 70.0 3.15 (dd, 10.0 & 9.5) 3.09-3.24 (m) 3.12 (ddd, 10.0, 9.5 & 5.5) 3.03-3.10 (m) 5'' 70.0 76.5 68.9 75.9 3.98 (brs) 3.09-3.24 (m) 3.87 (dq, 9.5 & 6.0) 3.22-3.24 (m) 6'' 17.4 60.9 17.7 66.9 0.81 (d, 6.0) 3.58 (brd, 11.0) 3.32 (overlap) 1.05 (d, 6.0) 3.70 (brd, 10.0) 3.26-3.28 (m) 1''' 100.7 4.38 (d, 1.0) 2''' 70.3 3.39 (brs) 3''' 70.5 3.26-3.28 (m) 4''' 71.8 3.03-3.10 (m) 5''' 68.2 3.26-3.28 (m) 6''' 17.7 0.99 (d, 6.0) OH-5 12.48 (s) 12.65 (s) 12.63 (s) 11.79 (s) 12.59 (s) glucopyranoside (aesculin). R R 1 2 H 4 Rha 2 2 Rha 5 2 Rha(16)Glc 3 2 Glc 6 7 Figure 1: Chemical structure of compounds 1-7 Vietnam Journal of Chemistry Flavonoids and phenolics from © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH www.vjc.wiley-vch.de 119 4. CONCLUSION From the 75 % methanol extract of the whole plants of Macrosolen bidoupensis, five flavonoids, including quercetin (1), quercitrin (2), isoquercitrin (3), astibin (4), and rutin (5), together with two phenolic glycosides, 3,3′-di-O-methylellagic acid 4- O-β-D-xylopyranoside (6), and aesculin (7) were purified. Their structures were elucidated using HR- ESI-MS, NMR data as well as comparison with published papers. All isolated compounds were detected from this species for the first time, whereas, compounds (3, 4 & 7) were notified for the first time from the Macrosolen genus. Acknowledgment. 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Corresponding author: Nguyen Tan Phat Institute of Chemical Technology Vietnam Academy of Science and Technology Thanh Loc 29, Thanh Loc, District 12, Ho Chi Minh City 70000, Viet Nam E-mail: ntphat@ict.vast.vn; Tel. +84- 916360751.