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| Author(s): |
Giovana Maria Lanchoti Fiori
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Ribeirão Preto. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Ciências Farmacêuticas de Ribeirão Preto (PCARP/BC) |
| Defense date: | 2016-09-08 |
| Examining board members: |
Norberto Peporine Lopes;
Silvia Helena Taleb Contini;
Regina Helena Queiroz Fornari;
Silvia Regina Cavani Jorge Santos
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| Advisor: | Norberto Peporine Lopes; Ana Maria Soares Pereira |
| Abstract | |
Cucurbitacin E is currently considered a drug candidate due to its anticancer activity, recognition of its molecular targets, and synergism with other drugs used for cancer treatment. However, the use of cucurbitacin E in clinical practice is not possible because of important research gaps regarding its preclinical and clinical pharmacokinetic characteristics. Cucurbitacin E is hydrolyzed to cucurbitacin I in plasma and in human liver microsomes. The aim of this study was to evaluate the population pharmacokinetics and plasma protein binding of cucurbitacin E and of its metabolite cucurbitacin I in rats. The method for the sequential analysis of cucurbitacins E and I in rat plasma was developed using LC-MS/MS. Plasma aliquots of 50 ?L were deproteinized with acetonitrile, the residues were reconstituted in acetonitrile:water (1:1, v/v), and clobazam was added as internal standard. The extracts were injected into an RP-18 column using a mobile phase consisting of a mixture of acetonitrile:water:methanol (32:35:33, v/v/v). The method was precise and accurate, showing linearities at a range of 1-100 ng cucurbitacin E/mL plasma and of 0.4-200 ng cucurbitacin I/mL plasma. The method was applied to the pharmacokinetic evaluation of cucurbitacin E administered to male Wistar rats at a single oral (gavage) or intravenous dose of 1 mg/kg dissolved in DMSO and phosphate-buffered saline, pH 7.4 (5:95, v/v). Serial blood samples were collected up to 24 h after oral or intravenous administration. The plasma concentrations of cucurbitacin E were quantified up to 16 h only after intravenous administration, while the plasma concentrations of cucurbitacin I remained below the limit of quantification after oral or intravenous administration. The population pharmacokinetic model was developed for administered intravenously cucurbitacin E using the NONMEM program, with adequate goodness of fit and predictive performance. The pharmacokinetic profile of intravenously administered cucurbitacin E was described by a two-compartment model with first-order distribution and elimination. The following pharmacokinetic parameters were obtained: release time (D) of 0.45 h, volume of distribution (Vd) of 27.22 L, clearance (Cl) of 4.13 L/h, and elimination half-life (t1/2) of 4.57 h. The interactions of cucurbitacin E and I with human (HSA) and rat (RSA) serum albumins were investigated using an optical biosensor by surface plasmon resonance (SPR) and circular dichroism (CD) spectroscopy. The binding data of the cucurbitacins to albumins were obtained by CD competition experiments with biliverdin. The SPR data revealed an undescribed binding event between cucurbitacin I and HSA and the binding affinities of cucurbitacin E and cucurbitacin I were higher for RSA than for HSA. Cucurbitacin E and cucurbitacin I can be classified as substances with high binding affinity for HSA and RSA. CD analysis showed that cucurbitacin E and cucurbitacin I modify the binding of biliverdin to albumins through opposite allosteric modulation (positive for HSA, negative for RSA), confirming that care should be taken when extrapolating the pharmacokinetic data between species. (AU) | |
| FAPESP's process: | 12/14408-9 - Disposition kinetics, plasma protein binding, metabolism in vitro and in vivo of curcubitacins in rats |
| Grantee: | Giovana Maria Lanchoti Fiori |
| Support Opportunities: | Scholarships in Brazil - Doctorate |