Effect of some phytoconstituents on Fe2+/ascorbate induced lipid peroxidation.

Transition metals like iron and copper, present inside the body system play a key role in the production of reactive oxygen radicals. These free radicals, causative agents of lipid peroxidation, not only damage proteins and DNA but also gradually changes the cellular membrane structure and ultimately leads to the loss of function and integrity. Uncontrolled lipid peroxidation results in various age related diseases, malignancy, infective diseases and injuries. Antioxidants and other phytochemical constituents present in the various plants are known to protect cells from such reactive oxygen species (ROS)-mediated damages. Here, we evaluated the effect of certain phytoconstituents present in the well-known medicinal plants on ROS scavenging using rat liver homogenate. The basal lipid peroxidation was found to be 0.1625±0.0095 ngMDA/min/mg protein, which got induced to 0.7938±0.0478 ngMDA/min/mg protein in the presence of Fe2+/ascorbate system. In this context, acteoside, berberine, catechin, 3´5-dihydroxyflavone7-o-ß-D-galacturonide-4-o-ß-D-glucopyranoside (a flavonoid glycoside from cumin), silibin and tetrahydrocurcumin decreased both basal and Fe2+/ascorbate induced lipid peroxidation as determined by thiobarbituric acid reaction. On the other hand, agnuside, andrographolide, picroside-I, negunoside, oleanolic acid, and glycerrihizin, showed enhancement in both basal and induced lipid peroxidation. Phytoconstituents which have decreased both basal and Fe2+/ascorbate induced lipid peroxidation may act as defensive against the deadly effects of ROS, causative agents of lipid peroxidation and other diseases either alone or in combination with diet/nutritional supplements.

Involvement of P-glycoprotein and CYP 3A4 in the enhancement of etoposide bioavailability by a piperine analogue.

Etoposide, a semi-synthetic derivative of podophyllotoxin, is widely used anticancer agent. Etoposide presents low bioavailability with wide inter-, and intra-patient variability after oral dosing. In an earlier study a piperine analogue, namely, 4-ethyl 5-(3, 4-methylenedioxyphenyl)-2E,4E-pentadienoic acid piperidide (PA-1), was shown to cause 2.32-fold enhancement of the absolute bioavailability of co-dosed etoposide in mice. In the present investigation a mechanistic evaluation was undertaken using various in vitro and animal-derived models. In everted rat gut sac studies PA-1 enhanced mucosal uptake of the drug while it inhibited efflux of Rh-123, a P-glycoprotein substrate from serosal-to-mucosal direction. In a single pass in situ perfusion experiment PA-1 significantly reduced the intestinal exsorption rate, exsorption clearance and the total plasma clearance of etoposide. On the other hand PA-1 did not alter the passive diffusion pattern of the drug in PAMPA assay. PA-1 was inhibitory to NADPH-assisted deethylation and demethylation reactions catalyzed by erythromycin N-demethylase, 7-methoxycoumarin-O-demethylase (MOCD) and ethoxyresorufin-O-deethylase (EROD). PA-1 was not cytotoxic to mucosal membrane and showed no adverse effect in acute toxicity determination. The results suggested that PA-1-mediated enhancement in the oral bioavailability of etoposide could possibly be due to its ability to modify P-gp/CYP 3A4 mediated drug disposition mechanisms.

Simultaneous determination of etoposide and a piperine analogue (PA-1) by UPLC-qTOF-MS: evidence that PA-1 enhances the oral bioavailability of etoposide in mice.

In the present investigation, a UPLC-qTOF-MS/MS method has been developed for the simultaneous determination of etoposide and a piperine analogue, namely, 4-ethyl 5-(3,4-methylenedioxyphenyl)-2E,4E-pentadienoic acid piperidide (PA-1). The analytes were separated on a reverse phase C18 column using methanol-water (72:28, v/v) mobile phase with a flow rate of 250 microL/min. The qTOF-MS was operated under multiple reaction monitoring mode using electro-spray ionization (ESI) technique with positive ion polarity. The major product ions for etoposide and PA-1 were at m/z 185.1350 and 164.1581, respectively. The recovery of the analytes from mouse plasma was optimized using solid phase extraction technique. The total run time was 6 min and the elution of etoposide and PA-1 occurred at 1.24 and 2.84 min, respectively. The calibration curves of etoposide as well as PA-1 were linear over the concentration range of 2-1000 ng/mL (r(2), 0.9829), and 1-1000 ng/mL (r(2), 0.9989), respectively. For etoposide intra-assay and inter-assay accuracy in terms of % bias was in between -7.65 to +6.26, and -7.83 to +5.99, respectively. For PA-1 intra-assay and inter-assay accuracy in terms of % bias was in between -7.01 to +9.10, and -7.36 to +6.71, respectively. The lower limit of quantitation for etoposide and PA-1 were 2.0 and 1.0 ng/mL, respectively. Analytes were stable under various conditions (in autosampler, during freeze-thaw, at room temperature, and under deep-freeze conditions). The method was used for a pharmacokinetic study which showed that PA-1 enhanced the oral bioavailability of etoposide in mice by 2.32-fold.

Modulation of P-glycoprotein ATPase activity by some phytoconstituents.

In the present investigation 16 phytoconstituents, which are active moieties found in several medicinal herbs, have been evaluated for their P-glycoprotein (P-gp) stimulation/inhibition profiles using a P-gp-dependent ATPase assay in rat jejunal membrane (in vitro). Acteoside, agnuside, catechin, chlorogenic acid, picroside -II and santonin showed an inhibitory effect. Negundoside, picroside -I and oleanolic acid caused a stimulatory effect. Andrographolide, apocyanin, berberine, glycyrrhizin, magniferin and piperine produced a biphasic response (stimulation at low concentration and inhibition at high concentration). The results suggested that a possible interaction of these phytoconstituents at the level of P-gp, could be an important parameter in determining their role in several key pharmacodynamic events.

Kinetics of the uptake of rifampicin and tetracycline into mouse macrophages. In vitro study of the early stages.

The in vitro uptake by mouse peritoneal macrophages, of chlortetracycline (by fluorescence microscopy) and of tetracycline and rifampicin (by scintillation spectrometry of radioactive antibiotics) has been studied over a six hours period, using various concentrations of the antibiotics, close to the therapeutic concentrations. The incidence of the conditions of the assays, especially that of the use of heterologous serum for the cultivation of cells, has been investigated; a medium supplemented with homologous serum at low concentration has been devised with the technique. The uptake of these antibiotics was a three-phases process suggesting the superposition to a passive diffusion of either an active incorporation, or a restriction of the outflow (perhaps associated). This led to a rather high concentration of the antibiotics into cells, although other studies have shown that this concentration is not as active on intracellular bacteria as one could expect from the in vitro sensitivity.