Piperine and piplartine ( Fig. 1) are naturally occurring amides from Piper species (Piperaceae), which have been used in folk medicine of tropical and subtropical countries for treatment of asma, bronchitis, fever, hemorrhoidal afflictions, gastrointestinal diseases, rheumatism, and as food additive.1-3) The amide piperine is the pungent principle of black pepper (P. nigrum) and can be extracted from dried fruits with a yield of 3-7%.4) Several biological activities have been associated to piperine, including inhibition of liver metabolism, antioxidant, central nervous system depressant and antitumoral activities. [4][5][6][7][8][9] Piplartine is one of the major amide isolated from the roots of P. tuberculatum (popularly known as "long pepper"), which has been largely used in the folk medicine as a sedative and antidote for snake bite. Piplartine has shown significant cytotoxicity against cell tumor lines, as well as antifungal, antimitotic and anti-platelet aggregation compound.9-13) Piplartine anticancer potential has been highlighted by the undergoing preclinical evaluation. In vivo studies using murine tumors demonstrated that in spite of a moderate anticancer activity, piplartine has weak toxicological side effects. 3,14) Additionally, it increases 5-fluorouracil anticancer efficacy, while reduces chemotherapeutical side effects, as evidenced by the prevention of 5-FUinduced leucopenia.15) These data suggests that piplartine is a promising anticancer compound to be used in combination of already known antineoplastic agents.The study of the oxidative metabolism on promising natural products is of major importance before they become medicines, since their oxidations can affect the drug's safety and efficacy, due to the formation of therapeutically active or toxic metabolites. 16) Thus, efforts have been addressed to describe the metabolic pathways of drug candidate compounds.The cytochrome P450 (CYP) enzymes are catalytic hemoproteins known for their role in the metabolism of non-polar comounds, present in all forms of life (plants, bacteria, mammals). They have played a key role in the oxidative transformation of endogenous and exogenous molecules. 17,18) The cytochrome P450 enzymes catalyze the hydroxylation of saturated carbon-hydrogen bonds, epoxidation of double bounds, oxidation of heteroatoms, dealkylation reactions, and oxidations of aromatic carbons, etc.17) The oxidative metabolism of drugs by cytochrome P450 monooxygenases has been extensively studied through biological models, such as direct experiments on animals, the use of perfused organs or isolated cells. However, there are several ethical restrictions using animals and also experimental drawnbacks associated with the isolation of some hydrophilic and reactive metabolites that could bind to biological macromolecules, preparation of liver and cells (microsomes, hepatocytes) are of variable quality with low yields. [18][19][20] Thus, alternative model systems of cytocrome P450 have been employed in studies of P450 functions, as well as in syn...

Palavras-chave: Piperina; piplartina; oxidação biomimética; metaloporfirinas; espectrometria de massas. Piperine and piplartine are alkaloids isolated from species of Piper genus. The choice of these molecules for this study was based on the promising biological activities presented by these substances, especially for their antitumoral potential. Based on the research of alternative ways for studying the metabolism of new drugs, especially from natural products, the goal of this study was to investigate the oxidative profile of piperine and piplartine through different metalloporhyrins, which biomimic the metabolism of cytochrome P450. For doing this research, piperine and piplartine were exposed to oxidation in homogeneous media, using iodosilbenzene (PhIO) as oxygen donor and synthetic metalloporphyrins of first and second generations as catalysts for the reaction, that were [Fe(TPP)]Cl, [Mn(TPP)]Cl, [Fe(TFPP)]Cl and [Mn(TFPP)]Cl. The solvents used for the reaction media were 1, 2-dichloroetane and acetonitrile. The standards and reaction media containing the oxidation products were analysed by gas chromatography coupled to mass spectrometry (GC-MS) with electron ionization (EI), and by mass spectrometry and mass spectrometry tandem with electrospray ionization (ESI-EM and ESI-EM/EM), in positive mode. Through the analysis of spectra obtained by GC-MS and ESI-MS, it was possible to observe the presence of the oxidation products, formed with all the metalloporphyrins tested, especially the fluoreted ones from the second generation. Despite having been detected small formation of oxidized product on piperine, this was practically insignificant. Piplartine shown to be a more reactive substrate in front of the catalysts tested. In piperine, it was possible to verify the presence of the hydroxylated product. In piplartine, the oxidized products observed were the demetoxilated, monohydroxilated and dihydroxilated, the last two being verified only through the technique of electrospray. The structures were proposed based on their fragment patterns presented on spectra of EI-MS (low resolution) an ESI-MS with high resolution in positive mode. The results of this work are promising to obtain oxidized derivatives of piperine and piplartine through synthetic metalloporphyrins.

This study evaluates the carvedilol‐lercanidipine drug interaction, and the influence of chronic kidney disease (CKD) on both drugs. Patients with high blood pressure (8 with normal renal function [control] and 8 with CKD with estimated glomerular filtration rate categories of G3b to G5 [12‐38 mL/min/1.73 m2]) were included and prescribed 3 different treatment regimens, a single oral dose of racemic carvedilol 25 mg (CAR), a single oral dose of racemic lercanidipine 20 mg (LER), and single oral doses of CAR plus LER. Blood samples were collected and variations in heart rate were assessed (using isometric exercise with handgrip) for up to 32 hours. Lercanidipine pharmacokinetics were not enantioselective, and were not affected by carvedilol and CKD. Carvedilol pharmacokinetics (data presented as median) were enantioselective with higher plasma exposure of (R)‐(+)‐carvedilol in both control (103.5 vs 46.0 ng ∙ h/mL) and CKD (190.6 vs 98.9 ng ∙ h/mL) groups. Lercanidipine increased the area under the plasma concentration–time curve of only (R)‐(+)‐carvedilol in the CKD group (190.6 vs 242.2 ng ∙ h/mL) but not in the control group (103.5 vs 98.7 ng ∙ h/mL). CKD increased plasma exposure (46.0 vs 98.9 ng ∙ h/mL) and effect‐compartment exposure (5.5 vs 20.9 ng ∙ h/mL) to (S)‐(–)‐carvedilol, resulting in higher β‐adrenergic inhibition (10.0 vs 6.1 bpm). Therefore, carvedilol dose titration in CKD patients with estimated glomerular filtration rate categories of G3b to G5 should be initiated, with no more than half the dose used for patients with normal renal function.

A doença renal crônica (DRC) está associada com inibição da atividade de sistemas enzimáticos e de transportadores de fármacos. O carvedilol, um β-bloqueador não seletivo é substrato e inibidor da P-gp intestinal. A lercanidipina, antagonista de canais de cálcio é metabolizada pelo CYP3A4, sendo descrita como provável inibidora da P-gp. O presente estudo avalia a interação carvedilol-lercanidipina em pacientes hipertensos portadores ou não de DRC. Foram investigados 8 pacientes hipertensos portadores de DRC estágios 3 e 4 e 8 pacientes hipertensos com função renal normal, fenotipados para o CYP2D6 e CYP3A, e genotipados para o CYP2C9 e P-gp. Os pacientes receberam dose única oral de 25 mg de carvedilol racêmico (Fase 1) ou 20 mg de lercanidipina racêmica (Fase 2) ou dose única oral de 25 mg de carvedilol racêmico associada com 20mg de lercanidipina racêmica (Fase 3). As amostras seriadas de sangue foram coletadas até 32h. A freqüência cardíaca foi avaliada na situação de exercício isométrico durante 2 min com o handgrip, a 30% da contratilidade voluntária máxima, em cada tempo de colheita de sangue. As concentrações plasmáticas dos enantiômeros do carvedilol e da lercanidipina foram realizadas por LC-MS/MS. A farmacocinética do carvedilol, como monoterapia ou em associação com a lercanidipina, é enantiosseletiva no GRUPO DRC com acúmulo plasmático do enantiômero (+)-(R)carvedilol. A administração de dose única oral de 20 mg de lercanidipina racêmica ao GRUPO DRC reduziu o clearance total aparente e aumentou a AUC somente para o enantiômero (+)-(R)-carvedilol. O GRUPO CONTROLE também apresentou acúmulo plasmático do enantiômero (+)-(R)-carvedilol. No entanto, a administração de dose única oral de 20 mg de lercanidipina racêmica não alterou a farmacocinética de ambos os enantiômeros do carvedilol no GRUPO CONTROLE. A comparação do GRUPO DRC com o GRUPO CONTROLE, na monoterapia ou em associação com lercanidipina, mostra que a DRC não altera a farmacocinética de ambos os enantiômeros do carvedilol. A relação PK-PD não mostra diferenças com significância estatística entre as Fases 1 e 3, tanto para o grupo DRC quanto para o grupo CONTROLE. No entanto, a comparação do GRUPO DRC com o GRUPO CONTROLE permite observar maiores valores de ECe50 nos pacientes do GRUPO DRC na Fase 3. A administração de dose única oral de 20 mg de lercanidipina, sob monoterapia ou em associação ao carvedilol, aos GRUPOS DRC e CONTROLE não mostra enantiosseletividade no parâmetro AUC. A administração de dose única oral de 25 mg de carvedilol racêmico reduziu de maneira enantiosseletiva o clearance total da (S)-lercanidipina no GRUPO DRC, mas não no CONTROLE. A comparação do GRUPO DRC com o CONTROLE não mostra diferenças com significância estatística nos parâmetros farmacocinéticos de ambos os enantiômeros da lercanidipina nas Fases 2 e 3. Concluindo, o carvedilol reduziu o clearance total aparente do eutômero (S)-lercanidipina e a lercanidipina reduziu o clearance total aparente do enantiômero (+)-(R)-carvedilol nos pacientes do Gupo DRC, mas n...