Synthesis, physicochemical properties and antiviral activities of ester prodrugs of ganciclovir

The purpose of this study was to synthesize a series of diester prodrugs of ganciclovir (GCV), for improving ocular and oral bioavailability and therapeutic activity. Solubility, logP, pH stability profile, in vitro antiviral activity, cytotoxicity, inhibition profile and ocular tissue hydrolysis of the GCV prodrugs were measured. Val-Val-GCV and Val-Gly-GCV diesters were found to exhibit greater aqueous stability compared to Val-GCV and Gly-Val-GCV while ocular tissue hydrolysis demonstrated Val-Gly-GCV and Gly-Val-GCV to be more stable. Val-Val-GCV and Val-GCV diesters were the most lipophilic compounds and were predicted to possess a partition coefficient 295- and 12-fold greater than that of GCV, respectively. All the prodrugs possess much higher aqueous solubility than the parent drug GCV. Ex vivo uptake in the rabbit eye indicates that the prodrugs have high uptake potential. The prodrugs showed no increase in cytotoxicity compared to GCV, instead there was a marked increase in their potency against human cytomegalovirus (HCMV) as well as HSV-1 and HSV-2. This should allow therapeutic response to be seen at a lower concentration that can be achieved more easily, than the drugs currently being used. In conclusion, the diester GCV prodrugs demonstrated excellent chemical stability, high aqueous solubility and markedly enhanced antiviral potency against the herpes viruses without any increase in cytotoxicity.     

灯盏乙素酯类前药的合成、理化性质及降解研究

目的对口服难吸收中药活性成分灯盏乙素进行结构改造，为寻找和设计合理前药及其剂型提供依据。方法通过先成盐后酯化的方法合成灯盏乙素乙酯、苄酯并改进文献方法合成羟乙酰胺酯，用质谱和氢谱确证结构。研究3种前药在不同pH水溶液中的稳定性、溶解度、分配系数和在人血浆中的降解。制备灯盏乙素羟乙酰胺酯环糊精包合物和乳剂，比较包合物和乳剂在肠液中对该前药的保护作用，考察该前药在不同肠段黏膜匀浆中的降解情况。结果合成的3种前药经确证为目标物；灯盏乙素羟乙酰胺酯在缓冲液(pH 4.2)和水中的溶解度比灯盏乙素分别提高近10倍和35倍，分配系数也由原来的-2.56提高到1.48；该酯水溶液的稳定性较好(t_1/2≈16 d，pH 4.2)，在人血浆的半衰期最短(t_1/2≈7 min)，但在肠黏膜匀浆中的降解可能影响酯的吸收，不同肠段黏膜匀浆降解羟乙酰胺酯的次序为：十二指肠>回肠≥空肠>结肠。乳剂在肠黏膜匀浆中对前药有显著的保护作用，包合物次之。结论与灯盏乙素乙酯和苄酯比较，羟乙酰胺酯的理化性质较好，但其在肠道中的稳定性有待提高，可以选择乳剂或结肠定位给药减少前药的降解。     

In-vitro hydrolysis, permeability, and ocular uptake of prodrugs of N-[4-(benzoylamino)phenylsulfonyl]glycine, a novel aldose reductase inhibitor

To enhance the ocular uptake of N-[4-(benzoylamino)phenylsulfonyl]glycine (BAPSG), two ester (methyl and isopropyl) prodrugs were synthesized and evaluated for their stability in various buffers (pH 1-9), hydrolysis in rabbit ocular tissues (cornea, conjunctiva, iris-ciliary body, lens, aqueous humor, and vitreous humor), transport across cornea and conjunctiva, and in-vivo uptake following topical administration. Over the pH range of 1-9, the rate constants for degradation ranged from 5.67 to 218.9 x 10(-3) h(-1) for the methyl ester and from 3.14 to 4.45 x 10(-3) h(-1) for the isopropyl ester. At all pH conditions, the isopropyl ester was more stable when compared with the methyl ester. A change in buffer concentration at pH 7.4 did not influence the stability of the prodrugs. The prodrugs were rapidly hydrolysed in the tissue homogenates, with the rate constants for hydrolysis ranging from 1.98 to 7.2x 10(-3) min(-1) for the methyl ester and 3.32 to 6.53 x 10(-3) min(-1) for the isopropyl ester. The in-vitro permeability of the methyl ester was less than the parent drug across cornea and conjunctiva. Isopropyl ester levels were not detectable in the receiver chamber even at the end of the 4-h transport study. Following topical administration of BAPSG and the two prodrugs at a dose of 60 microg/eye, the lowest levels were seen in vitreous humor for parent compound and its methyl ester. In general, the tissue uptake of methyl ester was less than BAPSG. Isopropyl ester levels were below detection limits in all the ocular tissues. Lipophilic ester prodrugs of BAPSG showed good aqueous solution stability in tissue homogenates. However, these prodrugs lacking the free carboxylate anion exhibited reduced in-vitro permeability and in-vivo uptake, suggesting the importance of free carboxylate anion in the delivery of BAPSG.     

高效液相色谱法测定去氧氟尿苷在不同介质中的平衡溶解度和表观油水分配系数

目的测定去氧氟尿苷在不同介质中的平衡溶解度以及在正辛醇-水和正辛醇-缓冲液体系中的表观油水分配系数。方法采用HPLC法测定去氧氟尿苷的浓度,采用摇瓶法测定去氧氟尿苷的表观油水分配系数。结果37℃,pH=7时去氧氟尿苷在水中的平衡溶解度为2.570 1 g.L-1,在pH〈5磷酸盐缓冲液中的平衡溶解度较低;去氧氟尿苷在正辛醇和水相中表观油水分配系数Papp为0.97;当pH〈7时,受pH影响不显著,表现为亲水性。结论去氧氟尿苷在水中的平衡溶解度及油水分配系数与介质的pH值有关,可以通过改变pH值,增加该药物新剂型的稳定性。     

黄芩苷在不同pH值缓冲液中理化常数的测定

目的考察黄芩苷在不同pH值中的平衡溶解度与表观油水分配系数,为制剂研究奠定基础。方法采用摇瓶-紫外分光光度法测定温度为25和37℃时,黄芩苷在不同pH值磷酸盐缓冲溶液中的平衡溶解度及在正辛醇/缓冲液体系中的表观油水分配系数。结果 25℃时,黄芩苷在pH=2.0,3.0,4.0,5.0,6.0,6.8,7.4,8.0和9.0缓冲液中的平衡溶解度分别为0.032,0.034,0.119,0.873,3.329,12.96,11.49,4.605和11.87mg.mL-1,相应条件下表观油水分配系数(P)值分别为0.363,0.244,0.292,0.137,0.057,0.046,0.036,0.028和0.029。37℃时,黄芩苷在pH=2.0,3.0,4.0,5.0,6.0,6.8,7.4,8.0和9.0缓冲液中的平衡溶解度分别为0.028,0.048,0.095,0.950,4.881,14.15,26.65,14.48和17.89mg.mL-1,相应条件下表观油水分配系数(P)值分别为0.234,0.224,0.365,0.103,0.074,0.049,0.034,0.034和0.035。结论黄芩苷的平衡溶解度在酸性及中性条件下受温度影响很小,在碱性条件下随着温度升高而增加;黄芩苷在酸性条件下的P值比在碱性条件下大,Pmax=0.363(T=25℃,pH=2),Pmax=0.365(T=37℃,pH=4),随着碱性的增加P值变化不明显,且温度对黄芩苷的P值几乎无影响。     

延胡索乙素在不同溶剂中平衡溶解度及其油水分配系数的测定

目的测定延胡索乙素在各种溶剂中的平衡溶解度以及在正辛醇-水中的表观油水分配系数,为延胡索乙素经皮给药制剂的制备提供实验基础。方法采用紫外分光光度法测定延胡索乙素在不同pH缓冲液中的平衡溶解度;采用高效液相色谱(HPLC)方法,测定不同介质中延胡索乙素的平衡溶解度;采用摇瓶法测定延胡索乙素的表观油水分配系数。结果 32℃延胡索乙素在pH7.4缓冲液中的平衡溶解度为32.47mg/L,在酸性缓冲液中溶解度增大;32℃延胡索乙素在油酸、吐温80中有较好的增溶能力,其溶解度分别为22165.21mg/L、69653.86mg/L;延胡索乙素的表观油水分配系数为3.12。结论延胡索乙素水溶性差,在油酸和吐温80中有较好的增溶能力。     

青蒿素在不同溶剂中平衡溶解度和表观油水分配系数的测定

目的测定青蒿素在不同pH缓冲液和7种非极性溶剂中的平衡溶解度以及在正辛醇-水中的表观油水分配系数,为青蒿素新剂型的研究与开发提供实验基础。方法采用高效液相-柱后衍生化-紫外检测法测定青蒿素在不同pH缓冲溶液及7种非极性溶剂中的平衡溶解度;采用摇瓶法测定青蒿素的表观油水分配系数。结果 37℃时青蒿素在纯水中的平衡溶解度为82.4μg/mL,随着pH的增大平衡溶解度呈先增大（pH5.0～6.8）后减小（pH6.8～8.0）的趋势;37℃时青蒿素在肉豆蔻酸异丙酯（IPM）、油酸乙酯（EO）和中链甘油酸三酯（MCT）中平衡溶解度较大,分别为10.34、9.28、8.46mg/mL,青蒿素的正辛醇-水表观油水分配系数P为12.2（lgP=1.09）。结论青蒿素水溶性差,在非极性溶剂IPM、EO、MCT中平衡溶解度较大。     

盐酸吉西他滨的处方前研究

目的测定盐酸吉西他滨在不同pH缓冲液中的平衡溶解度以及在正辛醇-水和正辛醇-缓冲液体系中的表观油水分配系数,并对其水溶液的稳定性进行研究。方法采用HPLC法测定盐酸吉西他滨的含量,摇床法测定该药物的表观溶解度和油水分配系数。结果 25℃条件下,盐酸吉西他滨在水中的平衡溶解度为58.82 g.L-1,在酸性介质中的平衡溶解度相对增加;盐酸吉西他滨的表观油水分配系数LgP为-1.22;60℃条件下,盐酸吉西他滨水溶液在pH3.84~10.37内较稳定,pH小于2或pH大于11时,降解反应加快,药物含量明显下降。结论盐酸吉西他滨的水溶性较强,其水溶液在强酸和强碱环境下不稳定。     

基于HPLC法测定醋酸甲羟孕酮的平衡溶解度与油水分配系数

目的对醋酸甲羟孕酮(MPA)在不同溶剂中的平衡溶解度及其在正辛醇-缓冲液体系中的油水分配系数进行测定。方法采用HPLC法测定MPA的质量浓度,测定MPA在水、有机溶剂、缓冲溶液和加十二烷基硫酸钠的缓冲溶液中的平衡溶解度,采用摇瓶法结合HPLC法测定MPA在正辛醇-缓冲液体系中的质量浓度,从而计算油水分配系数。结果 37℃时,MPA在蒸馏水和丙酮中的平衡溶解度分别为0.52±0.04和238.70±0.47μg·mL~(-1);在体积分数为90%的乙醇溶液中的平衡溶解度最大;在加十二烷基硫酸钠的缓冲溶液中的平衡溶解度增大;在水中的表观油水分配系数为1.99(lgP=0.30),脂溶性较强;在pH值为1.2~6.8的缓冲溶液中,平衡溶解度随pH值的升高而减小,油水分配系数随pH值的升高而增大。结论该实验建立的测定方法可准确测定MPA的平衡溶解度和油水分配系数。     

Designing novel pH-sensitive non-phospholipid vesicle: Characterization and cell interaction

In an effort to enhance the oral bioavailability of scutellarin, ethyl, benzyl and N,N-diethylglycolamide ester of scutellarin were synthesized. The hydrolysis of the prodrugs follows first-order kinetics in aqueous solution, and produced a V-shaped pH profile. The N,N-diethylglycolamide ester is highly susceptible to enzymatic hydrolysis in human plasma (t_1/2 ≈ 7 min) with a high stability in aqueous solution (t_1/2 ≈ 16 day, pH 4.2). Compared with the solubility of scutellarin, the solubility of glycolamide ester was about ten times in pH 4.0 buffer, and about thirty five times in water. Its apparent partition coefficient increased significantly from −2.56 to 1.48. Glycolamide ester of scutellarin was chosen to investigate the intestinal metabolism and in vivo bioavailability. Degradation studies in the intestinal tract content and homogenates indicated intestinal metabolism before absorption was a crucial obstacle for the prodrug. N,N-Diethylglycolamide ester can be protected from the degradation in the intestinal lumen by an emulsion. A significant increase in the plasma AUC and C_max of the prodrug emulsion was observed in rats, compared with that of the scutellarin–cyclodextrin complex (P < 0.01). The emulsion of N,N-diethylglycolamide ester produces a 1.58-fold enhancement in apparent bioavailability and 1.4-fold increase in the absolute bioavailability compared to the scutallarin–cyclodextrin complex.     

盐酸苯环壬酯油水分配系数的测定及pH值对其的影响

目的： 测定盐酸苯环壬酯油水分配系数,研究不同pH值对药物脂水分配系数的影响,为盐酸苯环壬酯新剂型的处方设计提供理论参考。方法： 本实验采用摇瓶-高效液相色谱法测定盐酸苯环壬酯在不同pH值条件下正辛醇-水/缓冲液体系中的表观脂水分配系数。结果： 盐酸苯环壬酯的脂水分配系数lgP值为1.29±0.16;在pH为1.2,3.0,4.5,5.0,5.5,6.0,6.8,7.0,8.0,9.0的环境中,脂水分配系数lgP值分别为0.31,0.72,1.16,1.34,1.99,2.26,2.22,1.61,2.34,3.24。结论： 盐酸苯环壬酯的脂水分配系数与介质的pH值有关,在pH 4.5~8.0生理条件下,盐酸苯环壬酯的脂溶性较好,水溶性差。     

Determination of the partition coefficients, acid dissociation constants, and intrinsic solubility of carbenoxolone

The dissociation constants, partition coefficients, and solubility of carbenoxolone (1) were determined using tritium-labeled drug. The partition and solubility methods were used to assess the dissociation constants of carbenoxolone, while the pKa of the structurally related triterpenoid, enoxolone (2) was determined using a spectrophotometric method. The true partition coefficient (TPC) of carbenoxolone was found to be 643.8 in an n-octanol:aqueous buffer system, while its intrinsic solubility (So) was 1.63 x 10(-5) M. The apparent partition coefficient (APC) was independent of the concentration of carbenoxolone over the pH range of 3 to 7. The values of pk1 and pk2 for carbenoxolone, obtained by the partition and solubility methods, were in reasonably good agreement. The observed pKa value of enoxolone enabled the assignment of pk2 (the weaker acid grouping) to the carboxyl group at C-30.     

布洛芬平衡溶解度及表观油水分配系数的测定

目的：测定布洛芬在不同pH磷酸盐缓冲溶液中的平衡溶解度与表观油水分配系数。方法采用紫外－可见分光光度法测定布洛芬的质量浓度,气浴恒温振荡－摇瓶法测定布洛芬的平衡溶解度及表观油水分配系数。结果37℃时布洛芬在pH2．0、3．0、4．0、5．0、6．0、6．8、7．4、8．0、9．0缓冲溶液中的平衡溶解度分别为0．05874、0．04078、0．06404、0．1930、1．027、2．551、4．613、3．866、4．409mg? mL －1;表观油水分配系数分别为10．19、17．11、12．55、6．390、4．911、5．976、4．925、2．599、1．716。结论布洛芬在磷酸盐缓冲溶液中的平衡溶解度及表观油水分配系数与介质的pH值相关,介质的pH值的增大,布洛芬的平衡溶解度增大;表观油水分配系数减小。     

田蓟苷在不同介质中的平衡溶解度及油水分配系数

目的：测定田蓟苷在不同缓冲溶液和表面活性剂溶液中的平衡溶解度及在正辛醇-水/磷酸缓冲盐中表观油水分配系数（P_app）,为今后新剂型的选择和制备提供参考。方法：通过高效液相色谱法测定田蓟苷在不同溶剂和表面活性剂溶液中的浓度,采用摇瓶法测定田蓟苷在正辛醇-水/磷酸缓冲盐中油水分配系数。结果：田蓟苷在37℃纯水中的平衡溶解度为1.57 mg·L^-1,在甲醇、乙酸乙酯及三氯甲烷有机溶液中溶解性较好;在酸性缓冲溶液中的平衡溶解度较水中有明显增加,在碱性缓冲液中随pH的增高平衡溶解度逐渐减小。在32 g·L^-1的十二烷基硫酸钠溶液中平衡溶解度提高到188.65 mg·L^-1。田蓟苷的油水分配系数为14.63（lg P=1.17）,且随溶液pH的增高逐渐增加。结论：田蓟苷为疏水性药物,脂溶性较强。制剂时,可加入适当浓度的十二烷基硫酸钠助溶。同时,提高其制剂的溶出度可能会提高其生物利用度。     

磺胺二甲嘧啶的溶解度及油水分配系数的研究

目的:研究磺胺二甲嘧啶(SM2)在不同pH值下的平衡溶解度和油水分配系数(Ko/w),为SM2制剂的开发提供基础研究。方法:配制不同pH值的磷酸盐缓冲液,采用饱和法测定其表观溶解度;通过SM2分配平衡后在油相(正辛醇)和水相的浓度比,计算油水分配系数。结果:SM2在pH2·0和pH9·0时平衡溶解度较高,分别为1·916、1·375g·L-1,油水分配系数在pH8·0时最高,为3·9070。结论:SM2在水中的平衡溶解度及油水分配系数与介质的pH值有关,pH<3·0或pH>6·8时溶解度较好。pH3～8时SM2在油相中分配较多,较易被机体吸收。     

乙酰天麻素平衡溶解度、油水分配系数及稳定性的测定

目的：测定乙酰天麻素平衡溶解度、油水分配系数及水解速率常数,为其制剂设计与吸收机制的研究提供依据。方法：建立乙酰天麻素UPLC分析方法,采用摇瓶法测定乙酰天麻素在不同pH值缓冲液中的平衡溶解度,以及在正辛醇-磷酸盐缓冲溶液中的油水分配系数,并考察其在60℃下不同pH值的水中的稳定性。结果：乙酰天麻素在水中的平衡溶解度约为300 μg·mL^-1,油水分配系数lgP值约为1.1,pH值的影响较小。乙酰天麻素在强酸性与碱性条件下易水解,在pH值5.0附近较为稳定。结论：乙酰天麻素在水中极微溶解,脂溶性较强,酸碱均可催化其发生水解反应。     

VBE-1平衡溶解度和表观油水分配系数的测定及其酸碱稳定性的考察

目的：测定VBE-1的平衡溶解度和表观油水分配系数,并考察其酸碱稳定性,为药物的制剂设计提供实验依据。方法：采用平衡法和摇瓶法测定VBE-1在不同溶剂中的平衡溶解度以及在正辛醇-水/缓冲溶液中的表观油水分配系数,采用高效液相色谱法测定两者的浓度,并用紫外分光光度法考察VBE-1的酸碱稳定性。结果：VBE-1在PEG-400中的溶解度较大,为（677.47±48.09）g·L^-1。在pH4.0~8.0范围内,pH对VBE-1的表观油水分配系数有影响,表现出表观油水分配系数随着pH升高而降低的趋势。pH的升高会引起VBE-1颜色的改变,但此变化为可逆反应。结论：VBE-1具有一定的透过能力,可满足经皮给药的一般要求,其对pH较敏感,实验过程中应避免在强碱条件下操作。     

Design of novel prodrugs for the enhancement of the transdermal penetration of indomethacin

A series of esters of indomethacin containing tertiary amine functional groups and designed for transdermal delivery were synthesized. The rates of chemical hydrolysis of all the esters in pH 7.4 phosphate buffer were determined. For N,N-diethylaminopropyl N-(4-chlorobenzoyl)-5-methoxy-2-methyl-3-indole acetate (ester 4), the rates of chemical hydrolysis in pH 5.5–11.25 buffers were investigated in detail. Ester 4 was chemically stable and had a higher n-octanol/water partition coefficient and a greater solubility in water at pH 7.4 than indomethacin. Furthermore, the rate of transdermal penetration of ester 4 through cadaver skin in Franz cells was found to be more than 10-times faster than that of indomethacin itself. Ester 4 was found to possess surface-active properties (CMC = 0.5 mg/ml). Assuming that micelles cannot penetrate biologic membranes, a corrected permeability coefficient was calculated for ester 4 using only the monomer concentration. This value, 3.6 × 10⁻² cm/h, was 100-times greater than that of indomethacin. These results suggest that prodrugs with structures similar to that of ester 4 may be useful for enhancing transdermal penetration of other carboxylic acid-containing anti-inflammatory agents.     

Anandamide prodrugs. 1. Water-soluble phosphate esters of arachidonylethanolamide and R-methanandamide.

Phosphate esters of arachidonylethanolamide (AEA) and R-methanandamide were synthesized and evaluated as water-soluble prodrugs. Various physicochemical properties (pK(a), partition coefficient, aqueous solubility) were determined for the synthesized phosphate esters. The chemical stability of phosphate esters was determined at pH 7.4. In vitro enzymatic hydrolysis rates were determined in 10% liver homogenate, and in a pure enzyme-containing (alkaline phosphatase) solution at pH 7.4. The intraocular pressure (IOP) lowering properties of R-methanandamide phosphate ester were tested on normotensive rabbits. The phosphate promoiety increased the aqueous solubility of the parent compounds by more than 16500-fold at pH 7.4. Phosphate esters were stable in buffer solutions, but rapidly hydrolyzed to their parent compounds in alkaline phosphatase solution (t(1/2)<15 s) and liver homogenate (t(1/2)=8-9 min). The phosphate ester of R-methanandamide reduced IOP in rabbits. These results indicate that the phosphate esters of AEA and R-methanandamide are useful water-soluble prodrugs.     

pH值对吡罗昔康理化性质及其经皮渗透性能的影响

目的:研究pH值对吡罗昔康理化性质及经皮渗透性能的影响,为其经皮给药制剂的研究提供实验依据。方法:用HPLC法测定药物在水、不同pH缓冲液(PBS)中的溶解度;采用双波长分光光度法测定药物的解离常数(pKa);摇瓶法测定药物的表观油水分配系数(logP);利用透皮扩散池以稳态渗透速率常数(Js)和通透系数(Ps)为评价指标研究药物的透皮效果。结果:吡罗昔康的pKa为6.33。32℃时,吡罗昔康在pH 7.4的缓冲液中logP为0.17,且溶解度和Js均达到最大,分别为(420.445)μg.mL-1和(64.612±0.011)μg.cm-2.h-1;Ps为(0.154±0.014)cm.h-1。结论:调节药物pH值,使药物维持较高的溶解度和分子型药物比例,可望获得理想的皮肤通透性。