Evaluation of the Impact of Esterases and Lipases from the Circulatory System against Substrates of Different Lipophilicity

Esterases and lipases can process amphiphilic esters used as drugs and prodrugs and impact their pharmacokinetics and biodistribution. These hydrolases can also process ester components of drug delivery systems (DDSs), thus triggering DDSs destabilization with premature cargo release. In this study we tested and optimized assays that allowed us to quantify and compare individual esterase contributions to the degradation of substrates of increased lipophilicity and to establish limitations in terms of substrates that can be processed by a specific esterase/lipase. We have studied the impact of carbonic anhydrase; phospholipases A1, A2, C and D; lipoprotein lipase; and standard lipase on the hydrolysis of 4-nitrophenyl acetate, 4-nitrophenyl palmitate, DGGR and POPC liposomes, drawing structure–property relationships. We found that the enzymatic activity of these proteins was highly dependent on the lipophilicity of the substrate used to assess them, as expected. The activity observed for classical esterases was diminished when lipophilicity of the substrate increased, while activity observed for lipases generally increased, following the interfacial activation model, and was highly dependent on the type of lipase and its structure. The assays developed allowed us to determine the most sensitive methods for quantifying enzymatic activity against substrates of particular types and lipophilicity.     

Computer-Aided Search for 5-Arylideneimidazolone Anticancer Agents Able To Overcome ABCB1-Based Multidrug Resistance

ABCB1 modulation is an interesting strategy in the search for new anticancer agents that can overcome multidrug resistance (MDR). Hence, 17 new 5-arylideneimidazolones containing an amine moiety, as potential ABCB1 inhibitors, were designed, synthesized, and investigated. The series was tested in both parental (PAR) and multidrug-resistant (MDR) ABCB1-overexpressing T-lymphoma cancer cells using cytotoxicity assays. The ABCB1-modulating activity was examined in rhodamine 123 accumulation tests, followed by Pgp-Glo™ Assay to determine the influence of the most active compounds on ATPase activity. Lipophilic properties were assessed both, in silico and experimentally (RP-TLC). Pharmacophore-based molecular modelling toward ABCB1 modulation was performed. The studies allowed the identification of anticancer agents (p-fluorobenzylidene derivatives) more potent than doxorubicin, with highly selective action on MDR T-lymphoma cells (selectivity index >40). Most of the investigated compounds showed ABCB1-modulating action; in particular, two 5-benzyloxybenzylidene derivatives displayed activity nearly as strong as that of tariquidar.     

Lipophilicity of Flavonoids Estimated by Reversed-Phase High Performance Thin-Layer Chromatography: Chemically Bonded Plates vs. Impregnated Plates with Oils,Animal, and Human Fats

Silica gel plates impregnated with a variety of oils (olive oil, sunflower oil, corn oil, trioctylamine, and paraffin oil) and fats (margarine, butter, cod liver fat, pig fat, sheep fat, pullet fat, and human fat) were evaluated and compared with the commercially available reversed-phases TLC plates (RP-18, RP-18 W, and CN). A representative series of flavonoids is employed to evaluate the suitability of oils and fats as reversed-phases for TLC and to provide different lipophilicity indices: R_M0, scores corresponding to first principal component of R_F and/or R_M, arithmetic mean of R_F and R_M values obtained with solvent mixture containing various concentrations of methanol in water. The retention results were excellent (r > 0.96) and allowed for accurate estimation of lipophilicity of selected flavonoids and to ranking the lipophilicity of oils and fats when comparing with chemically bonded phases. The human fat-impregnated plates provided lipophilicity values closely associated with those obtained for margarine and butter. Moreover, the human fat lipophilic character seems to be placed between pullet and cod fats. Concerning the lipophilicity scale of vegetable oils, it is worth noting that the corn oil presents the highest lipophilicity, closely followed by the sunflower and olive oils.     

柚皮苷-卵磷脂包合物的制备及其理化性质研究

柚皮苷是一种天然抗氧化剂,具有多种生物活性,但是存在脂溶性差、口服吸收率低等问题。为了提高柚皮苷的脂溶性和生物利用度,本研究制备了柚皮苷-卵磷脂包合物,并采用紫外(UV),红外(IR),差示量热扫描(DSC),X-射线衍射(XRD)等波谱分析方法研究了该包合物的理化性质。研究结果表明,柚皮苷与卵磷脂并没有形成一种新的化合物,柚皮苷只是以一种无定形状态分散在卵磷脂中,二者是通过氢键、范德华力等非共价键形式相结合。同时对比了柚皮苷与柚皮苷-卵磷脂包合物中柚皮苷在正辛醇中的溶解性,结果表明,与卵磷脂形成包合物后,柚皮苷在正辛醇中的溶解度由3.28μg/m L增加至755.50μg/m L,脂溶性得到了显著的提高;亚油酸体系中抗氧化能力实验表明,柚皮苷与卵磷脂的包合可以显著提高柚皮苷在脂溶性体系中的抗氧化能力。     

Synthesis and in vivo bioactivity of lipophilic alendronate derivatives against osteoporosis

New lipophilic alendronate amidated derivatives 1a–1d anchored alkyl chains (C_nH_2n+1, n?=?12, 14, 16, 18) had been obtained through the reaction of alendronate with carboxylic acid under anhydrous condition. The physicochemical parameters, such as the solubility and partition coefficient P_o/w in n-octanol/water, were determined through calculation by performing reversion phase high-performance liquid chromatography (RP-HPLC). The results showed that the derivatives had improved lipophilicity compared with alendronate. The in vivo bioactivities of the derivatives were investigated using the hindlimb unloading growing rats’ model. The results showed that the derivatives had in vivo bioactivity against hindlimb unloading growing rats’ bone loss, which indicated that the lipophilic derivative would be a promising new potent bisphosphates for treatment of the osteoporosis.     

Nickel‐Catalyzed Synthesis of Phosphonium Salts from Aryl Halides and Triphenylphosphine

An efficient method to synthesize functionalized tetraarylphosphonium salts is described. The nickel‐catalyzed coupling reaction between aryl iodides, bromides, chlorides, or triflates and triphenylphosphine generates tetraarylphosphonium salts in high yields. The coupling is wide in scope and tolerates a variety of functional groups such as alcohols, amides, ketones, aldehydes, phenols, phosphines and amines.     

Highly Hydrophilic and Lipophilic Derivatives of Bile Salts

Lipophilicity of 15 derivatives of sodium cholate, defined by the octan-1-ol/water partition coefficient (log P), has been theoretically determined by the Virtual log P method. These derivatives bear highly hydrophobic or highly hydrophilic substituents at the C3 position of the steroid nucleus, being linked to it through an amide bond. The difference between the maximum value of log P and the minimum one is enlarged to 3.5. The partition coefficient and the critical micelle concentration (cmc) are tightly related by a double-logarithm relationship (VirtuallogP=−(1.00±0.09)log(cmcmM)+(2.79±0.09)), meaning that the Gibbs free energies for the transfer of a bile anion from water to either a micelle or to octan-1-ol differ by a constant. The equation also means that cmc can be used as a measurement of lipophilicity. The demicellization of the aggregates formed by three derivatives of sodium cholate bearing bulky hydrophobic substituents has been studied by surface tension and isothermal titration calorimetry. Aggregation numbers, enthalpies, free energies, entropies, and heat capacities, ΔC_P,demic, were obtained. ΔC_P,demic, being positive, means that the interior of the aggregates is hydrophobic.