Afshin Zarghi

Rapid determination of metformin in human plasma using ion-pair HPLC

A rapid, simple and sensitive ion-pair HPLC method has been developed for quantification of metformin in plasma. The assay enables the measurement of metformin for therapeutic drug monitoring with a minimum detectable limit of 20 ng/ml. The method involves simple, one-step extraction procedure and analytical recovery was complete. The separation was performed on an analytical 150 x 4.6 mm i.d. mubondapak C(18) column. The wavelength was set at 235 nm. The mobile phase was 40% acetonitrile, 0.01 M sodium dodecyl sulphate, 0.01 M sodium dihydrogen phosphate, and distilled water to 100%, adjusted to pH 5.1 at a flow rate of 1.5 ml/min. The calibration curve was linear over the concentration range 0.2-2.5 microg/ml. The coefficients of variation for inter-day and intra-day assay were within the range of clinical usefulness.

Role of glutathione conjugation in protection of weanling rat liver against acetaminophen-induced hepatotoxicity

The rate of glutathione (GSH) conjugate formation to acetaminophen (APAP) in livers of weanling and adult rats treated with a single i.p. dose of APAP was compared. HPLC analysis of cytosolic fractions revealed that rate of conjugation in weanling rat is 24-times greater than that of adults. Increased rate of GSH conjugation was independent of of the age-related difference observed in liver GSH content. The normal level of liver GSH in weanling rat was 57% of adult level. APAP treatment depleted GSH more significantly in weanling rats as compared to that in adults. N-acetylcystein (NAC) alone had little influence on liver GSH levels. However it was successful in reducing GSH depletion in tissues of growing rats. A 32% repletion in hepatic GSH level in NAC-treated weanling rats was associated with a further 13-fold increase in the rate of GSH conjugate formation. These data together with histopathological results, clearly showed that the inducible GSH system in weanling rat liver act as a safe guard against APAP toxicity. A surge in the rate of APAP-GSH conjugation in growing liver may function in compensation of other detoxification pathways which are saturated more readily at this age.

Synthesis and calcium antagonist activity of 1,4-dihydropyridines containing phenylaminoimidazolyl substituents

Alkyl ester analogues of nifedipine, in which the ortho-nitrophenyl group at position 4 is replaced by 2-methylthio-1-phenylamino-5-imidazolyl substituent, were synthesized and evaluated as calcium-channel antagonists using the high K(+) contraction of guinea-pig ileal longitudinal smooth muscle. The results for the symmetrical esters showed that in the series of alkyl esters increasing the length of methylene chain in C-3 and C-5 ester substituents for more than two methylene units decreases activity. In the phenylalkyl ester series increasing the length of methylene chain also decreases activity. The results demonstrate that most of the compounds had similar activity to the reference drug nifedipine. In addition, two compounds, 5b and 5f were more active than the nifedipine.

Synthesis, docking simulation, biological evaluations and 3D-QSAR study of 5-Aryl-6-(4-methylsulfonyl)-3-(metylthio)-1,2,4-triazine as selective cyclooxygenase-2 inhibitors.

A series of 5-Aryl-6-(4-methylsulfonyl)-3-(metylthio)-1,2,4-triazine derivatives were synthesized and their COX-1/COX-2 inhibitory activity as well as in vivo anti-inflammatory and analgesic effects were evaluated. All of compounds showed strong inhibition of COX-2 with IC50 values in the range of 0.1-0.2μM and in most cases had stronger anti-inflammatory and analgesic effects than indomethacin at doses 3 and 6mg/kg. Among them, 5-(4-chlorophenyl)-6-(4-(methylsulfonyl) phenyl)-3-(methylthio)-1,2,4-triazine (9c) was the most potent and selective COX-2 compound; its selectivity index of 395 was comparable to celecoxib (SI=405). Evaluation of anti-inflammatory and analgesic effects of 9c showed its higher potency than indomethacin and hence could be considered as a promising lead candidate for further drug development. Furthermore, the affinity data of these compounds were rationalized through enzyme docking simulation and 3D-QSAR study by k-Nearest Neighbour Molecular Field Analysis.

Sensitive and rapid HPLC method for determination of memantine in human plasma using OPA derivatization and fluorescence detection: application to pharmacokinetic studies.

A rapid, sensitive and reproducible HPLC method was developed and validated for the analysis of memantine in human plasma after derivatization with o-phthaldialdehyde (OPA) and fluorescence detection. Amantadine was used as internal standard. The derivatized memantine and amantadine were eluted in less than 10 min with no interference from endogenous plasma peaks. The analysis was carried out on a monolithic silica column (Chromolith Performance RP-18e, 100×4.6 mm). The mobile phase was composed of a mixture of acetonitrile and 0.025 M phosphate buffer (50:50, v/v, pH=4.6) with a flow rate of 2.5 mLmin−1. The excitation and emission wavelengths were set at 335 nm and 440 nm respectively. The assay enables the measurement of memantine for therapeutic drug monitoring with a lower quantification limit of 2 ngmL−1. The method involves simple extraction procedure and analytical recovery was 82.8± 0.9%. The calibration curve was linear over the concentration range 2–80 ngmL−1. The coefficients of variation for inter-day and intra-day assay were found to be less than 8%. The method was successfully applied to pharmacokinetic studies in humans.

Kinetic studies of aflatoxin B1-glutathione conjugate formation in liver and kidneys of adult and weanling rats

Aflatoxin B1(AFB1)-glutathione(GSH) conjugation is the major pathway for the detoxification of aflatoxin metabolites. This reaction is catalysed by GSH S-transferase (GST) and play a major role in modulation of AFB1 adduct formation to nuclear DNA. Changes recorded in hepatic GST activity during development of rats can alter the balance between AFB1-GSH conjugation and AFB1-DNA adduct formation. Measurment of cytosolic GST using 1-chloro-2,4-dinitrobenzene (CDNB) as the substrate showed that the enzyme activity is initially lower in weanling tissues as compared to that of adults. But nevertheless hepatic and renal cytosolic GST activity is increased significantly in growing rats pretreated with AFB1. Kinetic studies of AFB1-GSH conjugate formation in kidneys and livers of the two-age groups of rats treated with a single i.p. dose of AFB1 (400 microg/kg b.w.) revealed that at the end of 24 h of AFB1 administration the rate of the conjugate formation in kidneys of immature rats was approximately twice of that measured in adults. Age-related differences in the GST activity as well as AFB1-GSH conjugation was more pronounced in kidneys. The conjugate formation in kidneys of growing rats during 6-24 h following AFB1 administration shows that urinary excretion of aflatoxin metabolites is relatively rapid in growing rats. The major portion of the AFB1-GSH is formed in liver but contribution of the renal tissue to the formation of detoxification metabolites can not be ruled out. These data demonstrate that aflatoxin metabolites are eliminated more efficiently from kidneys of a growing rat. AFB1-induced GST induction in renal tissues of growing animals during 24 h of the carcinogen administration could be considered as an important mechanism for GSH conjugate formation and aflatoxin detoxification. Therefore GST induction in response to hepatotoxic drugs can confer resistance to young animals being exposed for the first time to such drugs. It is also worthmentioning that the GST activity measured before AFB1 administration does not reflect the rate of AFB1 detoxification via GSH conjugation.

Design and synthesis of 1,3-diarylurea derivatives as selective cyclooxygenase (COX-2) inhibitors

A group of 1,3-diarylurea derivatives, possessing a methylsulfonyl pharmacophore at the para-position of the N-1 phenyl ring, in conjunction with a N-3 substituted-phenyl ring (4-F, 4-Cl, 4-Me, 4-OMe), were designed and synthesized for evaluation as selective cyclooxygenase-2 (COX-2) inhibitors. In vitro COX-1/COX-2 isozyme inhibition structure-activity studies identified 1-(4-methylsulfonylphenyl)-3-(4-methoxyphenyl) urea (4e) as a potent COX-2 inhibitor (IC(50)=0.11 microM) with a high COX-2 selectivity index (SI=203.6) comparable to the reference drug celecoxib (COX-2 IC(50)=0.06 microM; COX-2 SI=405). The structure-activity data acquired indicate that the urea moiety constitutes a suitable scaffold to design new acyclic 1,3-diarylurea derivatives with selective COX-2 inhibitory activity.

Substituted oxadiazoles: a patent review (2010 – 2012)

Introduction: The oxadiazoles represent a class of five-membered heterocyclic compounds which are of considerable interest in different areas of medicinal chemistry and drug discovery. Oxadiazoles can exist in different regioisomeric forms and employ in various agents with a broad range of biological activities. This review covers the work reported on various biological activities of oxadiazole derivatives from 2010 to 2012. Areas covered: Oxadiazole derivatives attract great attention due to their different kinds of pharmaceutical activities including antiviral, antimicrobial, anticancer, anticonvulsant, antidiabetic and anti-inflammatory activity. This paper provides a general review of oxadiazole derivatives published in international journals and patented between 2010 and 2012. Expert opinion: Oxadiazoles have been used frequently in drug-like molecules as bioisosteres for ester and amide functionalities and displayed numerous prominent pharmacological effects. The broad pharmacological profile of oxadiazole derivatives has attracted the attention of many researchers to explore this scaffold to its multiple potential against several activities. Therefore, oxadiazole motif is likely to be present in other therapeutic molecules in the future.

Design, synthesis and biological evaluation of new (E)- and (Z)-1,2,3-triaryl-2-propen-1-ones as selective COX-2 inhibitors.

A group of (E)-and (Z)-1,2,3-triaryl-2-propen-1-one derivatives possessing a methylsulfonyl COX-2 pharmacophore at the para position of the C-1 phenyl ring were synthesized and evaluated as selective COX-2 inhibitors. In vitro COX-1/COX-2 structure-activity relationships were determined by varying the substituents on the C-3 propenone moiety. Among the 1,2,3-triaryl-2-propen-1-ones, (Z)-1-(4-(methylsulfonyl)phenyl)-2,3-diphenylprop-2-en-1-one (3b) showed the most potency and selectivity on COX-2 inhibition (COX-2 IC(50) = 0.07 microM; selectivity index = 201). The Z-propenones were also found to be more potent and selective than their E-isomers for COX-2 inhibitory activity. The structure-activity data acquired indicate that the geometry of propenone and also the type of substituents on the C-3 propenone are important for COX-2 inhibitory activity.

Estrogen Receptor Ligands: A Review (2013–2015)

Estrogen receptors (ERs) are a group of compounds named for their importance in both menstrual and estrous reproductive cycles. They are involved in the regulation of various processes ranging from tissue growth maintenance to reproduction. Their action is mediated through ER nuclear receptors. Two subtypes of the estrogen receptor, ERα and ERβ, exist and exhibit distinct cellular and tissue distribution patterns. In humans, both receptor subtypes are expressed in many cells and tissues, and they control key physiological functions in various organ systems. Estrogens attract great attention due to their wide applications in female reproductive functions and treatment of some estrogen-dependent cancers and osteoporosis. This paper provides a general review of ER ligands published in international journals patented between 2013 and 2015. The broad physiological profile of estrogens has attracted the attention of many researchers to develop new estrogen ligands as therapeutic molecules for various clinical purposes. After the discovery of the ERβ receptor, subtype-selective ligands could be used to elicit beneficial estrogen-like activities and reduce adverse side effects, based on the different distributions and relative levels of the two ER subtypes in different estrogen target tissues. Therefore, recent literature has focused on selective estrogen ligands as highly promising agents for the treatment of some types of cancer, as well as for cardiovascular, inflammatory, and neurodegenerative diseases. Estrogen receptors are nuclear transcription factors that are involved in the regulation of many complex physiological functions in humans. Selective estrogen ligands are highly promising targets for treatment of some types of cancer, as well as for cardiovascular, inflammatory and neurodegenerative diseases. Extensive structure-activity relationship studies of ER ligands based on small molecules indicate that many different structural scaffolds may provide high-affinity compounds, provided that some basic structural requirements are present.