Research on chemical constituents and biological activities of two species garcinia cowa roxb. ex choisy and garcinia hanburyi hook. f growing in Vietnam

From the results of the chemical and biological activity studies of two plant species, the acacia tree (G.

cowa) and the canopy tree (G. hanburyi), it can be seen that these two plants have great potential for detection ofnew compounds or compounds with many important biological activities, especially those with cytotoxic activity.

Therefore, there is a need for further research into these two plant species to detect compounds with unique new structures or potential biological activities.

Gambogic acid isolated from wisteria exhibited many important biological activities, especially cytotoxic

activity on many cancer cell lines. Therefore, it is necessary to continue to study gambogic acid metabolism in order to obtain derivatives with higher biological activity and lower toxicity than the first; at the same time, to conduct further bioactivity tests to understand the mechanism of action of GA and its derivatives for application in supportive treatment products.

pdf27 trang | Chia sẻ: honganh20 | Ngày: 05/03/2022 | Lượt xem: 232 | Lượt tải: 0download
Bạn đang xem trước 20 trang tài liệu Research on chemical constituents and biological activities of two species garcinia cowa roxb. ex choisy and garcinia hanburyi hook. f growing in Vietnam, để xem tài liệu hoàn chỉnh bạn click vào nút DOWNLOAD ở trên
ent signal of H-8 at δH 7.51. On the 13C NMR spectrum of the compounds isolated, there appeared characteristic carbon signals of xanthone frame containing 1-3 prenyl or geranyl substituents. The results of synthesis of carbon signals in xanthone frame of GC1-GC17 compounds are summarized in Table 4.1 below. Table 4.1. Signals of the displacement of carbon in the xanthone frame Position δCaC Note C-O C-H C-C or C- prenyl/geranyl 1 160.0-162.7 - - GC7: δC 158.0 (C-O) 2 - 98.3-98.4 104.5-112.2 3 161.5-164.5 - - GC7: δC 159.9 (C-O) 4 - 92.2-93.9 107.8 4a 155.1-157.1 - - 5 - 100.9-103.9 111.4-113.9 GC3: δC 119.8 (C-H) 5a 152.9-157.9 - - 6 152.3-157.8 125.3 - GC3: δC 125.3 (C-H) 7 142.6-147.2 - - GC3: δC 151.4 (C-O) 8 - 105.0-109.4 129.2-139.8 8a - - 109.5-113.8 GC3: δC 121.9 (C-C) 9 179.9-183.5 - - 9a - - 101.7-103.9 a Measured in CDCl3, c125 MHz. The structure of substances was determined based on the NMR, HRESIMS spectral data combined with comparison with the published compounds in the reference. The results determined the structure of 17 xanthone, including 06 new xanthone: cowaxanthone IK (GC1-GC3), norcowanol AB (GC4-GC5), garcinone F (GC6) and 03 compounds were isolated for the first time from G. cowa plants: garcinone D (GC16), fuscaxanthone I (GC17) and parvifoliol F (GC18). The following presents the results of structural elucidation of two compounds GC1 and GC4. 4.1.1. GC1 Compound: Cowaxanthone I (New Compound) GC1 compounds are isolated in the form of yellow iridescent needles with a melting point of 204-205 oC. On the HRESIMS spectrum (Figure 4.2), the protonated molecular ion peak [M + H] + at m / z 429,1907 (theoretical calculation for C24H29O7 is 429,1908), so the CTPT of GC1 is determined as C24H28O7. Spectra 1H and 13C NMR of GC1 appeared signals suggesting GC1 has the structure of a monogeranylated xanthone. In the low field on 1H NMR spectrum there are resonance signals of three aromatic protons at δH 7.50 (1H; s; H-8); 6.80 (1H; s; H-5) and 6.32 (1H; s; H-4). There was also a signal of a methoxy group oscillating at δH 3.96 (3H; s; 7-OCH3) and a hydrated geranyl group (figure 4.3). On 13C NMR spectrum there are signals of 15 Csp2 with specific signals for xanthone frame. That is the signal of a carbonyl group at δC 181.0 (C-9) and the signal of a phenolic carbon conjugated to the carbonyl group at δC 161.1 (C-1). 13C NMR spectra also showed the signal of 6 aromatic carbon attached to oxygen at δC 161.1 (C-1); 164.1 (C-3); 157.2 (C-4a); 155.7 (C-5a); 153.9 (C-6) and 147.2 (C-7). The signal of methoxy carbon appears at δC 56,7 (7-OCH3) and the signal of a third Csp3 linked to oxygen at δC 71.5 (C-7 ') (Figure 4.4). 11 Figure 4.3. 1H NMR spectra of GC1 compound Figure 4.4. 13C NMR spectra of GC1 compound The aromatic proton signal at low field δH 7.50 is attributable to H-8 due to the electron attraction effect of the conjugated carbonyl group at C-9. HMBC spectrum also shows interaction of H-8 with C-9, C-8a (δC 113,6) and C-7. The methoxy group is attributed to the C-7 position by the HMBC interaction of the methoxy group proton and H-8 with C-7. The remaining two aromatic protons are attributed to H-5 (δH 6.80) and H-4 (δH 6,32) due to HMBC interaction of H-5 proton with C-9, C-7, C- 6 and the proton H-4 with C-9, C-2 (δC 111,8), C-3. The presence of the hydrated geranyl group was determined by signals on the spectrum 1H, 13C NMR, HSQC and HMBC. On the HMBC spectrum appears interactions of proton H-1 '(δH 3.33) with phenolic carbon C-1 and with C-2, C-3; interaction of proton alken at δH 5.27 (1H; t; 6.0; H-2 ') with two methylene carbon C-1' (δC 22,1), C-4 '(δC 41 , 3) and a C-10 'methyl carbon (δC 16,1); interaction of the H-4 'methylene proton (δH 1.98) with a quaternary alken carbon C-3' (δC 135.6) and two carbon methylene C-5 '(δC 23,7), C-6 '(δC 44,3). The position of the hydroxy group on the geranyl group was determined at C-7 'due to the HMBC interaction of the two methylene proton groups H-5', -6 '(δH 1.47 and 1.40, respectively) and the proton of the two. methyl group H-8 ', -9' (δH 1.15) with C-7 '. The spectral data of GC1 are given in Table 4.2, the molecular structure and the main interactions on the HMBC spectrum of GC1 compounds are shown in Figure 4.5. 7 6 5 5a 8a 8 O 4a 9a 9 4 3 2 1 O H3CO HO OH 1' OH 2' 3' 4' 5' 6' 7' 8' 9'10' OH O O H3CO HO OH OH OH H H H Figure 4.5. Chemical structure and main HMBC interaction of GC1 compound Table 4.2. NMR spectral data of GC1 and GC2 compounds Position GC1 GC2 Hab (mult; J) CaC HMBC (HC) Hab (mult; J) CaC HMBC (HC) 1 161,1 161,1 2 111,8 111,6 3 164,1 164,0 4 6,32 (s) 94,0 2, 3, 4a, 9a, 9 6,33 (s) 93,9 2, 3, 4a, 9a, 9 4a 157,2 157,2 5 6,80 (s) 103,7 5a, 8a, 7, 6, 9 6,79 (s) 103,4 5a, 8a, 7, 6, 9 5a 155,7 155,3 6 153,9 153,2 7 147,2 144,7 8 7,50 (s) 105,7 5, 5a, 6, 7, 8a, 9 7,45 (s) 109,1 5, 5a, 6, 7, 9 8a 113,6 113,8 9 181,0 181,1 9a 103,2 103,2 1’ 3,33 (m) 22,1 3, 1, 3’, 2’, 2 3,33 (m) 22,1 3, 1, 3’, 2’, 2 12 2’ 5,27 (t; 6,0) 123,8 1’, 4’, 10’ 5,27 (t; 7,0) 123,8 1’, 4’, 10’ 3’ 135,6 135,6 4’ 1,98 (m) 41,3 2’, 3’, 5’, 6’, 10’ 1,98 (t; 7,0) 41,3 2’, 3’, 5’, 6’, 10’ 5’ 1,47 (m) 23,7 3’, 7’, 6’, 4’ 1,47 (m) 23,6 3’, 7’, 6’, 4’ 6’ 1,40 (m) 44,3 5’, 8’, 9’, 4’, 7’ 1,39 (m) 44,2 5’, 8’, 9’, 4’, 7’ 7’ 71,5 71,5 8’ 1,15 (s) 29,2 6’, 7’, 9’ 1,15 (s) 29,1 6’, 7’, 9’ 9’ 1,15 (s) 29,2 6’, 7’, 8’ 1,15 (s) 29,1 6’, 7’, 8’ 10’ 1,80 s) 16,1 2’, 3’, 4’ 1,79 (s) 16,1 2’, 3’, 4’ OCH3 3,96 (s) 56,7 7 - - - a Measured in CD3OD, b 500 MHz, C 125 MHz Based on the analysis of HRESIMS spectrum and 1D, 2D NMR spectra of GC1 compound, we determined GC1 to be 1,3,6-trihydroxy-7-methoxy-2- (7-hydroxy-3,7-dimethyloct- 2-enyl) xanthone. This is a new compound, isolated from nature for the first time and named cowaxanthone I. 4.1.2. GC4 Compound: Norcowanol A (New Compound) GC4 compounds isolated as pale yellow powder. On the HRESIMS spectrum (Figure 4.14) appears protonated molecular ion peak [M + H] + at m/z 499,2324 (theoretical calculation for CTPT C28H35O8 is 499,2326), so the CTPT of GC4 is determined. is C28H34O8. Figure 4.15. 1H NMR spectra of GC4 compound Figure 4.16. 13C NMR spectra of GC4 compound GC4's 1H and 13C NMR spectra showed signals that suggest the GC4 has the structure of a xanthone containing a hydrated geranyl group and a hydrated prenyl group. In the low field on the spectrum 1H and 13C NMR there are resonance signals of two aromatic CH groups at δH 6.27 (1H; s; H-4) / δC 93.1 and 6.69 (1H; s; H- 5) / δC 101.0. The signals of two doublet methylene groups appear at δH 3.41 (2H; d; 7.5; H-1 ') / δC 21.8 and 4.15 (2H; d; 6.5; H -1”) / δC 26.5 and singlet signal of 4 methyl groups suggest the existence of two substituent prenyl or geranyl groups on xanthone frame. The geranyl group was identified as 7-hydroxy-3,7-dimethyloct-2-enyl group based on NMR spectrum and HC interactions on HSQC and HMBC spectrum, in particular the signals of two methylene groups have the same displacement. chemically metabolized at δH 1.12 (3H; s; H-8 ", -9") / δC 29.1 and interacted on the HMBC spectrum of these two methyl groups with a tertiary Csp3 binding to oxygen at δC 71.5 (C-7”). There is also an HC interaction on the HMBC spectrum of the H-1 proton H-1” with the two C-2” carbon alkanes (δC 125,0), C-3” (δC 135,5) and the interaction of the alpha-alpha proton. -2” with 2 carbon methylene C-1”, C-4” (δC 41,3) and 1 methyl carbon C-10” (δC 16,5). The low field shift signal of the CH2-1” methylene group suggests that the geranyl group binds to C-8. On the HMBC spectrum also appears the interaction of H-1” with the carbon of the xanthone frame, namely C-7 (δC 142,5), C-8 (δC 129,2) and C-8a (δC 112, first). The prenyl group was defined as a 4-hydroxy-3-methylbut-2-enyl group based on the HMBC interaction of the proton H-1 'with C-2' carbon (δC 126.8) and C-3 '(δ C 135,1) and interaction of the singlet methylene proton binding to oxygen at δH 4.33 (3H; s; H-4 ') / δC 61.8 with C-2', C-3 carbon 'and C-5' (δC 21,7). The position of the prenyl group was determined at C-2 due to the HMBC interaction of H-1 'with C-1 (δC 161,5), C-2 (δC 110,3) and C-3 (δC 163.2). HMBC interactions of proton H-4 with C-2, C-3, C-4a (δC 156,4), C-9a (δC 103,9), C-9 (δC 183, 13 5) and the interaction of proton H-5 with carbon C-8a, C-7, C-6 and C-9 allows to locate the aromatic protons in the xanthone framework. The chemical structure and the main HMBC interactions of GC4 are presented below, the spectral data of GC4 compounds are presented in Table 4.4. 7 6 5 5a 8a 8 O 4a 9a 9 4 3 2 1 O HO HO 1'' OH 1' OH 2' 3' 5' 4'2'' 3''4'' 10'' 5''6'' 7'' 9'' 8'' OH OH O O HO HO OH OH OH H H OH Figure 4.17. Chemical structure and main HMBC interaction of GC4 compound The results of spectroscopic analysis of GC4 compounds showed that the structure of the compound almost coincided with the kaennacowanol A compound isolated from G. cowa [141], except for the signal dilatexpearance of the methoxy group. On the basis of analysis of HRESIMS spectrum and 1D, 2D NMR spectra of GC4 compound, GC4 compound was identified as 1,3,6,7-tetrahydroxy-2- (4-hydroxy-3-methylbut-2-enyl ) - 8- (7-hydroxy-3,7-dimethyloct-2-enyl) xanthone. This is a new compound, isolated from nature for the first time and named norcowanol A. 4.2. Research results on the chemical composition of G. hanburyi plants Research results on the chemical composition of DCM extract of G. hanburyi stem and resin obtained 8 caged xanthones GH1-GH8. The structures of the compounds are shown below. On the NMR spectrum of the compounds GH1- GH8 appeared specific signals for potential polyprenyl xanthone compounds with 4-oxotricyclo cage [,7] dec-8-en-2-one - a type xanthone frames are common in G. hanburyi trees. There are also signals characteristic of a pyrano ring formed by the reaction of the –OH group and the geranyl group. O O OH O O O CHO O R 5 CH3 CHO H 2 CH3 COOH isoprenyl 1 COOH CH3 isoprenyl R1 R2 R3 4 CH3 COOH H isoprenyl = 3 COOH CH3 H 6 CH3 CH3 H 7 R = CH3 8 R = n-butyl 2 3 4 5 6 7 8 9 10 11 12 13 1416 17 18 19 20 21 22 25 24 23 O O OH O O O R3 R2R1 ABCD Figure 4.61. Chemical structure of the compounds GHx (x = 1-8) isolated from G. hanburyi resin and sterm barks 1H NMR spectra of the caged xanthone frame of the compounds GH1-GH8 showed that the equivalent proton signals had similar shifts. It is the singlet signal of the phenolic hydroxy proton conjugate with the carbonyl group at δH 12.70-13.00 (6-OH). The weak field proton doublet signal represents the signal of proton olefin conjugate with carbonyl group at δH 7,55-7,57 (d; 6,5-7,0; H-10). Proton signaling group characteristic for cage structure includes the signal of a methylene group appearing at δH 2.31 (1H; dd; 13,0; 5.0; H-21); 1,34-1,36 (1H; overlap; H- 21); one proton methine at δH 2.51 (1H; d; 9.5; H-22) and one proton methine at δH 3.47 (1H; m; H-11) for xanthone carrying a 4-oxotricyclo cage [,7] dec-8-en-2-one or at δH 2.81-2.89 for xanthone with 4-oxotricyclo cage frame [,7] decan-2-one . The signal of a pair of proton doublet has separation constant J = 10.0 at δH 6.61- 6.66 (H-4) and 5.38-5.54 (H-3) characterizing the double bond of pyrano ring (ring D) (table 4.17). Table 4.17. Signals of displacement of protons and carbon in the cage xanthone 14 Position Xanthone with caged frame 4- oxotricyclo[,7]dec-8-en-2-one Xanthone with caged frame 4- oxotricyclo[,7]decan-2-one Hab Cac Hab Cac 2 78,4-81,3 78,4-81,3 3 5,38-5,54 (d; 10,0) 124,5-126,5 5,38-5,54 (d; 10,0) 124,5-126,5 4 6,61-6,66 (d; 10,0) 115,3-115,9 6,61-6,66 (d; 10,0) 115,3-115,9 5 102,8-103,3 102,8-103,3 6 - 157,3 -157,8 - 157,3 -157,8 7 100,4-100,6 100,4-100,6 8 178,8-179,0 178,8-179,0 9 133,2-133,8 3,07-3,18 (m) 48,5-48,6 10 7,55-7,57 (d; 6,0-6,5) 134,9-135,6 4,37-4,42 (dd; 4,5; 1,5) 72,3-74,1 11 3,47 46,8-47,0 2,81-2,89 43,7-44,2 12 202,4-203,5 208,1-208,4 13 83,7-84,7 86,0-86,4 14 90,5-90,9 88,4-88,4 16 157,3-157,7 155,5-155,7 17 107,6-108,3 107,6-108,3 18 160,9-161,5 160,9-161,5 21 2,31 (dd; 13,0; 5,0); 1,34- 1,36 (overlap) 25,2-25,5 2,31 (dd; 13,0; 5,0); 1,34-1,36 (overlap) 20,0 22 2,51 (d; 9,5) 49,0-49,2 2,51 (d; 9,5) 43,6 23 83,2-84,1 82,1-82,4 24 1,69 (s) 29,7-30,1 1,69 (s) 29,7-30,1 25 1,29 (s) 27,2-29,1 1,29 (s) 27,2-29,1 a Measured in CDCl3, b 500 MHz, c 125 MHz. Signals of carbon displacement at the same position in cage-bearing xanthone with similar structure (6 xanthone with 4-oxotricyclo cage frame [,7] dec-8-en-2-one GH1- GH6 and two xanthone carrying 4- oxotricyclo cage frame [,7] decan-2-one GH7-GH8) almost coincide. In addition, it can be observed that when the cage xanthone frame is oxidized to a 4-oxotricyclo [,7] decan-2-one frame, the whole signal of carbon in the cage structure is shifted. The structure of substances was determined based on the associated NMR spectroscopy compared with the compounds published in the references. The results have isolated and determined structure of 08 caged xanthone, including gambogic acid (GH1), isogambogic acid (GH2), morellic acid (GH3), isomorellic acid (GH4), isomorellin (GH5), desoxymorellin (GH6), isomoreollin B (GH7) and 10α- butoxygambogic acid (GH8). The analysis results of spectral data of gambogic acid are presented below: 4.2.1. GH1 compound: Gambogic acid The compound GH1 was isolated from the resin extract and the stem of G. hanburyi tree branches in the form of an orange amorphous powder, polar angle of rotation [α] = -578o (c 0.201; CHCl3). Spectra 1H, 13C NMR and HSQC of GH1 allowed to determine the signals of 44 protons and 38 carbons, including 1 -OH group at δH 12,77; 8 methyl groups; 5 methylene groups; 6 groups -CH sp2; 2 groups of methine; 3 carbonyl carbon; 10 Csp2 does not contain C-H bonds, of which 3 carbons is bound to oxygen; 3 Csp3 of grade 4 associated with oxygen. 15 2 3 4 5 6 7 8 9 10 11 12 13 1416 17 18 19 20 21 22 25 26 28 29 24 23 27 O O OH O O O 34 35 33 32 31 30 40 39 38 37 36 HOOC ABCD O O O O O O HOOC H H H H H H HMBC COSY Figure 4.62. Chemical structure and COSY interaction, HMBC of compound GH1 Figure 4.63. 1H NMR spectra of the compound GH1 Figure 4.64. 13C NMR spectra of the compound GH1 Interactions on COSY, HSQC and HMBC spectrum showed that GH1 has structural fragments including: three prenyl groups, one of which contains a COOH group; a double coupling CH = CH; a spin system CHsp2- CHsp3-CH2-CHsp3 (Figure 4.62). These data suggest that GH1 has the structure of a substitute polyprenyl xanthone. On the HMBC spectrum, the interaction of the double-bonded proton appears at δH 5.38 (d; 10.0; H-3) and 6.60 (d; 10.0; H-4) with the quaternary sp3 carbon at δ C 81.3 (C-2). HMBC interactions between methylene protons at δH 1,76 (1H; overlap; H-20); 1.59 (1H; m; H-20) and 2.01 (2H; m; H-36) with C-2 (δC 81,3) help confirm the structural part related to D-ring of xanthone frame cage. Interactions between olefin singlet proton at low field δH 7.55 (1H; d; 7.0; H-10) with carbon include: 2 carbonyl carbon at δC 178.9 (C-8) and 203, 3 (C-12); carbon sp3 at δC 46.8 (C-11) and the HMBC interaction between protons at δH 2.51 (1H; d; 9.0; H-22) with (C-14) and (C-23) help make Unravel the structure related to the A ring in the cage xanthone frame. HMBC interaction between methylene protons of 3-carboxylbut-2-enyl groups at δH 2.95 (2H; d; 7.0; H-26) with carbon C-12, C-13, C-14 shows position of this group on the cage xanthone frame (figure 4.70). This suggests that the chemical structure of GH1 could be acid (Z) -4 - ((2R, 11S, 13R, 14S, 23S) -6-hydroxy-2,23,23-trimethyl-17- (3- methylbut-2-en-1- yl) -2- (4-methylpent-3-en-1-yl) -8,12-dioxo-2,8,11,12,13,23-hexahydro-7H, 4H -11,22-methanofuro [3,2-g] pyrano [3,2-b] xanthen-3a-yl) -2-methylbut-2-enoic (gambogic acid) conforms to molecular formula C38H44O8. Combining analysis of COSY, HSQC and HMBC spectra, we assigned the remaining carbon and proton signals. Results of NMR spectroscopy analysis and comparison with spectral data of GH1 with gambogic acid in the reference [36] are summarized in Table 4.18, showing that the spectral data completely coincides. Therefore, we conclude that the compound GH1 is gambogic acid. 4.3. Results of GA derivative synthesis 4.3.1. Results of molecular recovery in the glass state and supercooler state of amorphous gambogic acid Among the morphological forms of the active substance, the amorphous form is of more interest than the crystalline form because of its better solubility in water and higher biological activity. The amorphous form of a material is created by rapidly cooling the drug to avoid crystallization after melting it at its melting point. The molecular movement in amorphous materials is characterized by the time for α structure recovery in the supercooler and glass states. These materials have an out-of-order and temperature dependent structure, and at high temperature amorphous materials have liquid-like properties but at low temperature molecular recovery takes place slowly. these materials are much more like solids. The investigation of molecular recovery in the glass state 16 and supercooling state of GA is to evaluate the potential of GA medicinal use. The thermal properties of GA have been investigated on the basis of differential scanning calorimetry (DSC) in the temperature range from 273-373 K with the temperature rise rate of 10 K / min. The results have determined that the glass transition temperature of GA is Tg = 338K (Figure 4.87). Figure 4.87. DSC spectrum of a) GA increment; b) GA after being heated at 373 K for 3 minutes To investigate the molecular dynamics of the amorphous GA, wide-field dielectric spectroscopy (BDS) was measured in a wide frequency range from 10-1 to 106. During the measurement, the temperature increased from 153 to 333 K. with heating rates of 10 K / min and from 333 to 411 K with heating rates of 2 K / min. The GA BDS broadband dielectric spectrum from the supercooler and the glass form is shown in Figure 4.88 below. Figure 4.88. GA's broadband dielectric spectrum is at a) higher than the mirror transfer temperature and b) lower than the mirror transfer temperature. On the broadband dielectric spectrum of GA at a temperature lower than the glass phase transition temperature, two secondary molecular recovery processes β and can be observed in conjunction with the intermolecular motion of GA. Meanwhile, on the BDS spectrum at a temperature higher than the glass transfer temperature, a peak appears corresponding to the recovery of α structure and dc conductivity. GA's molecular recovery processes shift towards higher frequencies with increasing temperature, showing an increase in the degree of molecular motion with increasing temperature. By combining the experimental data measured in the BDS spectrum, combined with the Vogel – Fulcher – Tammann equation (VFT), the glass transition temperature Tg = 333 K (determined at the temperature at which the recovery time is is equal to 100 s). This result is deviated from the DSC method, but this error is normal and acceptable. Theoretical calculation results on the basis of the dependence of α structural recovery time on τα temperature (T = 300 K) also show that GA can exist in a dynamic stable state in about 2, 31,109 days. This proves that GA is quite durable and can be stored at room temperature. In addition, based on the VFT equation, the material brittleness of GA is mp = 103 (common substances mp = 16-200 [199]). When the brittleness is between 16 and 30, eg glass (SiO2) the material is considered very hard. With a material brittleness greater than 100, the material is considered very brittle. Between 30 and 100, the brittleness is medium. Hence, the GA in the supercooled state could be classified as a brittle material. Calculation results on the ECNLE software obtained the glass transfer temperature Tg = 338 K with the heating rate of 10 K / min completely consistent with the experiment. In addition, the calculation results also show that the process is closely related to molecular recovery and the kinetic formation of individual molecules, this process is also known as Johari – Goldstein recovery. . Thus, the large kinetic stability time and relative material 17 brittleness properties of GA show that GA can meet the physical requirements of an active substance with medicinal potential. This is an important basis to conduct GA derivative fusion reactions to obtain highly active derivatives with potential for practical application. 4.3.2. Research orientation O O OH O O O HOOC Figure 4.89. Chemical and crystalline structure of GA The crystal structure of GA shows that the xanthone ring structure is on one plane and has two different upper and lower sides. The two prenyl groups and the polycyclic ring are located above, forming the hydrophobic face, while the carboxylic acid group and the carbonyl group of the lower polycyclic ring form the hydrophilic face (figure 4.89). The results of the carboxylic group transformation suggest that the hydrophilic plane does not play an important role in binding to its biological target. The carboxyl -COOH group can be converted to other functional groups such as ester, amide or other base group without much influence on apoptosis activity. The structural-activity (SAR) studies of GA have shown the importance of coupling on the D ring (conjugation with C = O group of ring C) for activity. The derivatives generated from 6-OH group (B-ring) metabolism such as methylation or acylation have similar activity as the primary agent. Therefore, this 6-OH group does not play a decisive role in activity. From the above results of SAR analysis of GA, we selected to synthesize some GA derivatives by converting carboxylic acid group to ester and amide form with the aim of preserving active structural parts of GA. The metabolic reactions use the DCC / DMAP catalyst to activate the acid group. 4.3.3. Results synthesized derivatives The transformation of the COOH group of GA is done according to the diagram in Figure 3.4. The structure of the products and their reaction efficiency are presented in Table 4.26. Table 4.26. The structure of products and the yield of the reactions Symbol R Yield (%) Physical state Weight (mg) Note GA1 -OCH3 91 Yellow oil 220 GA2 -OC2H5 75 Yellow oil 175 GA3 N 70 Yellow oil 250 New compound GA4 N 84 Yellow oil 233 GA5 N O 79 Yellow oil 189 New compound GA6 NN CF3 51 Yellow oil 140 New compound GA7 N N F F 68 Yellow oil 126 New compound GA8 S N H 15 Yellow oil 52 New compound Gambogic acid metabolism results obtained 08 derivatives, of which 02 ester derivatives are methyl gambogate (GA1), ethyl gambogate (GA2) and 06 amide derivatives are N, N-diallylgambogamide (GA3), N- piperidinylgambogamide. (GA4), N-morpholinegambogamide (GA5), 1 (4-trifluoromethylbenzene-piperazinyl) gambogamide (GA6), 1- (2,5-difluorobenzyl) piperazinylgambogamide (GA7) and N- (2-thiophen-2-yl) 18 ethylgambogamide (GA8). In which, 05 derivatives N, N-diallylgambogamide (GA3), N- morpholinegambogamide (GA5), 1 (4-trifluoromethylbenzene-piperazinyl) gambogamide (GA6), 1- (2,5- difluorobenzyl) piperazinylgambogamide (GA7) and N- (2-thiophen-2-yl) ethylgambogamide (GA8) are new compounds. The structure of the synthetic products is determined by one-dimensional and two-dimensional NMR spectra. The clean compounds GA1-GA5 have been subjected to high resolution spectroscopy. The analytical results of spectral data of compounds GA1 and GA4 are presented below: GA3 compounds: N, N-diallyl gambogamide On the HRESIMS spectrum of compound GA3 appeared protonated molecular peak [M + H] + at m / z 708,3883 (calculated for CTPT C44H54NO7 is 708,3900). Therefore, the CTPT of the GA3 compound is C44H53NO7. Spectrum 1H, 13C NMR and HSQC of GA3 showed proton and carbon signals corresponding to allyl group at δH 5,61 (2H; m) / δC 133,6; 132.8 (2CH = allyl); δH 5.09-5.02 (4H; m) / δC 117.6 (2CH2 = allyl); δH 3.88 (2H; m) / δC 45.5 (CH2 allyl); δH 3.71; 3.61 (2H; dd; 16.0; 5.5) / δC 49.5 (CH2 allyl). The analysis results on the COSY spectrum did not show any interaction of allyl pr

Các file đính kèm theo tài liệu này:

  • pdfresearch_on_chemical_constituents_and_biological_activities.pdf
Tài liệu liên quan