K. Mohammad

Inhibition of dipeptidyl peptidase IV (DPP IV) is one of the mechanisms explaining the hypoglycemic effect of berberine

Berberine was investigated as an inhibitor of human dipeptidyl peptidase IV (DPP IV) in an attempt to explain its anti-hyperglycemic activities. The investigation included simulated docking experiments to fit berberine within the binding pocket of DPP IV. Berberine was found to readily fit within the binding pocket of DPP IV in a low energy orientation characterized with optimal electrostatic attractive interactions bridging the isoquinolinium positively charged nitrogen atom (berberine) and the negatively charged acidic residue of glutamic acid-205 (GLU205) of DPP IV. Experimentally, berberine was found to inhibit human recombinant DPP IV in vitro with IC50 = 13.3 μM. Our findings suggest that DPP IV inhibition is, at least, one of the mechanisms that explain the anti-hyperglycemic activity of berberine. The fact that berberine was recently reported to potently inhibit the pro-diabetic target human protein tyrosine phosphatase 1B (h-PTP 1B) discloses a novel dual natural h-PTP 1B/DPP IV inhibitor.

Inhibition of glycogen synthase kinase by curcumin: Investigation by simulated molecular docking and subsequent in vitro/in vivo evaluation

Curcumin was investigated as an inhibitor of glycogen synthase kinase-3β (GSK-3β) in an attempt to explain some of its interesting multiple pharmacological effects, such as its anti-diabetic, anti-inflammatory, anti-cancer, anti-malarial and anti-alzheimers properties. The investigation included simulated docking experiments to fit curcumin within the binding pocket of GSK-3β followed by experimental in vitro and in vivo validations. Curcumin was found to optimally fit within the binding pocket of GSK-3β via several attractive interactions with key amino acids. Experimentally, curcumin was found to potently inhibit GSK-3β (IC50 = 66.3 nM). Furthermore, our in vivo experiments illustrated that curcumin significantly increases liver glycogen in fasting Balb/c mice. Our findings strongly suggest that the diverse pharmacological activities of curcumin are at least partially mediated by inhibition of GSK-3β.

Intermittent fasting during Ramadan attenuates proinflammatory cytokines and immune cells in healthy subjects

Intermittent fasting and caloric restriction have been shown to extend life expectancy and reduce inflammation and cancer promotion in animal models. It was hypothesized that intermittent prolonged fasting practiced during the month of Ramadan (RIF) could positively affect the inflammatory state. To investigate this hypothesis, a cross-sectional study was designed to investigate the impact of RIF on selected inflammatory cytokines and immune biomarkers in healthy subjects. Fifty (21 men and 29 women) healthy volunteers who practiced Ramadan fasting were recruited for the investigation of circulating proinflammatory cytokines (interleukin [IL]-1β, IL-6, and tumor necrosis factor α), immune cells (total leukocytes, monocytes, granulocytes, and lymphocytes), and anthropometric and dietary assessments. The investigations were conducted 1 week before Ramadan fasting, at the end of the third week of Ramadan, and 1 month after the cessation of Ramadan month. The proinflammatory cytokines IL-1β, IL-6, and tumor necrosis factor α; systolic and diastolic blood pressures; body weight; and body fat percentage were significantly lower (P < .05) during Ramadan as compared with before Ramadan or after the cessation of Ramadan fasting. Immune cells significantly decreased during Ramadan but still remained within the reference ranges. These results indicate that RIF attenuates inflammatory status of the body by suppressing proinflammatory cytokine expression and decreasing body fat and circulating levels of leukocytes.

Discovery of DPP IV Inhibitors by Pharmacophore Modeling and QSAR Analysis followed by in silico Screening

Dipeptidyl peptidase IV (DPP IV) deactivates the natural hypoglycemic incretin hormones. Inhibition of this enzyme should restore glucose homeostasis in diabetic patients making it an attractive target for the development of new antidiabetic drugs. With this in mind, the pharmacophoric space of DPP IV was explored using a set of 358 known inhibitors. Thereafter, genetic algorithm and multiple linear regression analysis were employed to select an optimal combination of pharmacophoric models and physicochemical descriptors that yield selfconsistent and predictive quantitative structure–activity relationships (QSAR) (r2287=0.74, F‐statistic=44.5, r2BS=0.74, r2 LOO=0.69, r2PRESS against 71 external testing inhibitors=0.51). Two orthogonal pharmacophores (of cross‐correlation r2=0.23) emerged in the QSAR equation suggesting the existence of at least two distinct binding modes accessible to ligands within the DPP IV binding pocket. Docking experiments supported the binding modes suggested by QSAR/pharmacophore analyses. The validity of the QSAR equation and the associated pharmacophore models were established by the identification of new low‐micromolar anti‐DPP IV leads retrieved by in silico screening. One of our interesting potent anti‐DPP IV hits is the fluoroquinolone gemifloxacin (IC50=1.12 μM). The fact that gemifloxacin was recently reported to potently inhibit the prodiabetic target glycogen synthase kinase 3β (GSK‐3β) suggests that gemifloxacin is an excellent lead for the development of novel dual antidiabetic inhibitors against DPP IV and GSK‐3β.

Evaluation of immunosuppression induced by metronidazole in Balb/c mice and human peripheral blood lymphocytes.

The immunomodulatory effect of metronidazole (MTZ), a nitroimidazole drug used as an antiprotozoal and antibacterial agent, was investigated using Balb/c mice and human peripheral blood lymphocytes. For in vivo studies, mice were divided into six groups, six animals per group, group I received vehicle alone while the other groups (II-VI) received intraperitoneal injections of MTZ (14, 28, 42, 57, and 114 mg/kg) respectively. For in vitro studies different concentrations of MTZ (5, 10, 50, and 200 microg/ml) were used. MTZ showed a significant decrease in the percentage of circulating neutrophils and monocytes and an increase in the percentage of circulating lymphocytes. The relative weights of spleen as well as the relative body weight gain also decreased. Detectable changes were seen in the histology of spleen and thymus. Splenic plaque-forming cells (PFC), hemagglutination (HA) titer to sheep red blood cells (SRBC), spleenocytes and human peripheral blood lymphocytes proliferation (MLR) were markedly suppressed by MTZ treatment as compared to control group. MTZ also induced a significant decrease in delayed-type hypersensitivity (DTH) reaction, phagocytic activity (assessed by phagocytic capacity and phagocytic index) as well as TNF-alpha secretion by peritoneal macrophages. These observations indicate that MTZ significantly induced immunosuppression in mice and in human peripheral blood lymphocytes.

Olanzapine inhibits glycogen synthase kinase-3β: An investigation by docking simulation and experimental validation

Olanzapine was investigated as an inhibitor of glycogen synthase kinase-3beta (GSK-3beta) in an attempt to evaluate its effect on blood glucose level. The investigation included simulated docking experiments to fit olanzapine within the binding pocket of GSK-3beta followed by in vitro enzyme inhibition assay as well as in vivo subchronic animal treatment. Olanzapine was found to readily fit within the binding pocket of GSK-3beta in a low energy orientation characterized with optimal attractive interactions bridging the tricyclic thienobenzodiazepine nitrogen and sulfur atoms of olanzapine and the residue of VAL-135 of GSK-3beta. In vivo experiments showed a significant decrease in fasting blood glucose level in Balb/c mice at 1.0, 2.0 and 3.0 mg/kg dose levels (P<0.05) and 6 fold increase in liver glycogen level at the 3 mg/kg dose level (P<0.001). Moreover; olanzapine was found to potently inhibit recombinant GSK-3beta in vitro (IC(50) value=91.0 nM). Our findings strongly suggest that olanzapine has significant GSK-3beta inhibition activity that could justify some of its pharmacological effects and glucose metabolic disturbances.

Antioxidant, antihyperuricemic and xanthine oxidase inhibitory activities of Hyoscyamus reticulatus.

Context: Xanthine oxidase (XO) is a key enzyme in the pathophysiological homeostasis of hyperuricemia. It catalyzes the oxidation of hypoxanthine to xanthine and then to uric acid, the reaction involves the formation of free radical intermediates and superoxide byproducts. Objectives: This study was undertaken to investigate the antioxidant, antihyperuricemic, and xanthine oxidase inhibitory potentials of Hyoscyamus reticulatus L. (Solanaceae) extract. Materials and methods: The antioxidant potency was measured using the ABTS•+ scavenging capacity system, which includes Trolox as a standard. The xanthine oxidase inhibitory activity of the extract was quantitated in vitro by measuring the decline in the catalytic rate of xanthine oxidase following incubations with the plant extracts and using xanthine as a substrate. The hypouricemic potential of the extract was evaluated using an in vivo model for hyperuricemia. We tested three different doses of the extract and allopurinol was used as standard antihyperuricemic positive control. Results: H. reticulatus aqueous extract exhibited significant antioxidant scavenging properties (533.26 μmol TE/g dry extract weight) and inhibitory effect on xanthine oxidase activity (IC50 12.8 μg/mL). Furthermore, oral administration of the aqueous extract significantly reduced serum urate levels in oxonate-induced hyperuricemic mice in a dose-dependent manner. Discussion and conclusion: Our results suggest that the aqueous extract of H. reticulatus aerial parts might have great potential as an antioxidant and a hypouricemic agent. Our lab is currently identifying the active compounds in the extract to which the biological activities could be attributed.

Impact of Ramadan Intermittent Fasting on Oxidative Stress Measured by Urinary 15-F2t-Isoprostane

Fasting and caloric restriction have been associated with reduced incidence of chronic diseases and cancers. These effects have been attributed to reduced oxidative stress. Since Ramadan intermittent fasting (RIF) has been associated with reduced caloric intake, it was hypothesized that RIF would alleviate oxidative stress in healthy volunteers. The study was designed to elucidate the impact of RIF on oxidative stress measured by 15-F2t-Isoprostane (15FIP). Fifty healthy subjects (23 men and 27 women) who intended to fast Ramadan were recruited. Urine and serum sampling and anthropometric and dietary assessments were conducted one week before Ramadan (T0), at the end of the third week of Ramadan (T1), and one month after Ramadan (T2). Biochemical measurements included urinary 15FIP, creatinine, and hematological indices. Results revealed that the urinary level of 15FIP measured at T0 was normal, while they showed a significantly (P < 0.05) higher level when measured at T1 concomitant with a significant (P < 0.05) increase in the body weight and total body fat percent. In conclusion, results suggest that increased body weight is associated with increased lipid peroxidation and oxidative stress, and the impact of RIF on oxidative stress is mediated by the changes in body weight at the end of the month.

Xanthine oxidase inhibitory activity of the methanolic extracts of selected Jordanian medicinal plants

Background: The search for novel xanthine oxidase (XO) inhibitors with a higher therapeutic activity and fewer side effects are desired not only to treat gout but also to combat various other diseases associated with the XO activity. At present, the potential of developing successful natural products for the management of XO-related diseases is still largely unexplored. In the present study, we have screened the methanolic extracts of various Jordanian medicinal plants for their XO inhibitory activities using an optimized protocol. Materials and Methods: The methanolic extracts of 23 medicinal plants, belonging to 12 families, were tested in vitro, at 200 μg/ml concentrations, for their XO inhibitory potential. The dose-dependent inhibition profiles of the most active plants were further evaluated by estimating the IC50 values of their corresponding extracts. Results: Six plants were found most active (% inhibition more than 39%). These plants are Salvia spinosa L. (IC50 = 53.7 μg/ml), Anthemis palestina Boiss. (168.0 μg/ml), Chrysanthemum coronarium L. (199.5 μg/ml), Achillea biebersteinii Afansiev (360.0 μg/ml), Rosmarinus officinalis L. (650.0 μg/ml), and Ginkgo biloba L. (595.8 μg/ml). Moreover, four more plants, namely Lavandula angustifolia Mill. (28.7% inhibition), Helianthemum ledifolium (L.) Mill. (28.4%), Majorana syriaca (L.) Kostel. (25.1%), and Mentha spicata L. (22.5%) showed a XO inhibitory activity in the range of 22–30%. Conclusion: The study showed that many of the tested plant species are potential sources of natural XO inhibitors that can be developed, upon further investigation, into successful herbal drugs for treatment of gout and other XO-related disorders.

A Validated RP HPLC-PAD Method for the Determination of Hederacoside C in Ivy-Thyme Cough Syrup

A simple reversed phase high-performance liquid chromatographic (RP-HPLC) method coupled with a photodiode array detector (PAD) has been developed and validated for the analysis of hederacoside C, the marker of ivy plant, in Ivy-Thyme cough syrup. Separation of hederacoside C was achieved using a Phenomenex-Gemini C18 column isothermally at 40°C. A mobile phase system constituted of solvent A (water: acetonitrile: orthophosphoric acid (85%), 860 : 140 : 2 v/v) and solvent B (acetonitrile: orthophosphoric acid (85%), 998 : 2 v/v) was used, at gradient conditions, at a flow rate of 1.5 mL/min. Analysis was performed using UV-detection (205 nm). The method was linear over the range (0.03–0.15) mg/mL of hederacoside C (r = 0.9992). Repeatability and intermediate precision were acceptable (RSD <2%). Limits of detection (LOD) and quantitation (LOQ) were 0.011 and 0.032 mg/mL, respectively. Percentage recovery was found to lie between 99.69% and 100.90% (RSD <2%). The method was also proved to be specific (peak-purity coefficient = 0.996).