New Molecules of Diterpene Origin with Inhibitory Properties toward α-Glucosidase.

The incidence of diabetes mellitus (DM), one of the most common chronic metabolic disorders, has increased dramatically over the past decade and has resulted in higher rates of morbidity and mortality worldwide. The enzyme, α-Glucosidase (α-GLy), is considered a therapeutic target for the treatment of type 2 DM. Herein, we synthesized arylidene, heterocyclic, cyanoetoxy- and propargylated derivatives of quinopimaric acid (levopimaric acid diene adduct with p-benzoquinone) 1-50 and, first, evaluated their ability to inhibit α-GLy. Among the tested compounds, quinopimaric acid 1, 2,3-dihydroquinopimaric acid 8 and its amide and heterocyclic derivatives 9, 30, 33, 39, 44, with IC50 values of 35.57-65.98 µM, emerged as being good inhibitors of α-GLy. Arylidene 1ß-hydroxy and 1ß,13α-epoxy methyl dihydroquinopimarate derivatives 6, 7, 26-29, thiadiazole 32, 1a,4a-dehydroquinopimaric acid 40 and its indole, nitrile and propargyl hybrids 35-38, 42, 45, 48, and 50 showed excellent inhibitory activities. The most active compounds 38, 45, 48, and 50 displayed IC50 values of 0.15 to 0.68 µM, being 1206 to 266 more active than acarbose (IC50 of 181.02 µM). Kinetic analysis revealed the most active diterpene indole with an alkyne substituent 45 as a competitive inhibitor with Ki of 50.45 µM. Molecular modeling supported this finding and suggested that the indole core plays a key role in the binding. Compound 45 also has favorable pharmacokinetic and safety properties, according to the computational ADMET profiling. The results suggested that quinopimaric acid derivatives should be considered as potential candidates for novel alternative therapies in the treatment of type 2 diabetes.

Towards multi-target antidiabetic agents: Discovery of biphenyl-benzimidazole conjugates as AMPK activators.

Type 2 diabetes mellitus is a complex metabolic disorder requiring polypharmacology approaches for effective treatment. Combinatorial library of fifteen new tricyclic benzimidazole derivatives have been designed and synthesized to combine fragments commonly found in allosteric AMPK activators and AT1 receptor antagonists. It was found that 2'-cyanobiphenyl serves as the pharmacophore of AMPK-activating activity, which also increases with the expansion of the external hydrogenated cycle. Also, pronounced antiplatelet activity is characteristic of the studied compounds. One of derivatives was identified as a potent inhibitor of the formation of advanced protein glycation end-products with reactive dicarbonyl scavenging activity. Two submicromolar AMPK activators 2b and 3b prevents inflammatory activation of murine macrophages. Along with good water solubility and synthetic availability, these results render biphenyl derivatives of fused benzimidazoles as a valuable starting point for the development of AMPK activators with multi-target antidiabetic activity.

Neuroprotective Effect of Magnesium Acetyltaurate Against NMDA-Induced Excitotoxicity in Rat Retina.

Glutamate excitotoxicity plays a major role in the loss of retinal ganglion cells (RGCs) in glaucoma. The toxic effects of glutamate on RGCs are mediated by the overstimulation of N-methyl-D-aspartate (NMDA) receptors. Accordingly, NMDA receptor antagonists have been suggested to inhibit excitotoxicity in RGCs and delay the progression and visual loss in glaucoma patients. The purpose of the present study was to examine the potential neuroprotective effect of Mg acetyltaurate (MgAT) on RGC death induced by NMDA. MgAT was proposed mainly due to the combination of magnesium (Mg) and taurine which may provide neuroprotection by dual mechanisms of action, i.e., inhibition of NMDA receptors and antioxidant effects. Rats were divided into 5 groups and were given intravitreal injections. Group 1 (PBS group) was injected with vehicle; group 2 (NMDA group) was injected with NMDA while groups 3 (pre-), 4 (co-), and 5 (post-) treatments were injected with MgAT, 24 h before, in combination or 24 h after NMDA injection respectively. NMDA and MgAT were injected in PBS at doses 160 and 320 nmol, respectively. Seven days after intravitreal injection, the histological changes in the retina were evaluated using hematoxylin & eosin (H&E) staining. Optic nerves were dissected and stained in Toluidine blue for grading on morphological neurodegenerative changes. The extent of apoptosis in retinal tissue was assessed by TUNEL assay and caspase-3 immunohistochemistry staining. The estimation of neurotrophic factor, oxidative stress, pro/anti-apoptotic factors and caspase-3 activity in retina was done using enzyme-linked immunosorbent assay (ELISA) technique. The retinal morphometry showed reduced thickness of ganglion cell layer (GCL) and reduction in the number of retinal cells in GCL in NMDA group compared to the MgAT-treated groups. TUNEL and caspase-3 staining showed increased number of apoptotic cells in inner retina. The results were further corroborated by the estimation of neurotrophic factor, oxidative stress, pro/anti-apoptotic factors, and caspase-3 activity in retina. In conclusion, current study revealed that intravitreal MgAT prevents retinal and optic nerve damage induced by NMDA. Overall, our data demonstrated that the pretreatment with MgAT was more effective than co- and posttreatment. This protective effect of MgAT against NMDA-induced retinal cell apoptosis could be attributed to the reduction of retinal oxidative stress and activation of BDNF-related neuroprotective mechanisms.

Comparative angioprotective effects of magnesium compounds.

Magnesium (Mg) deficiency is implicated in the development of numerous disorders of the cardiovascular system. Moreover, the data regarding the efficacy of different magnesium compounds in the correction of impaired functions due to low magnesium intake are often fragmentary and inconsistent. The aim of this study was to compare the effects of the most bioavailable Mg compounds (Mg l-aspartate, Mg N-acetyltaurate, Mg chloride, Mg sulphate and Mg oxybutyrate) on systemic inflammation and endothelial dysfunction in rats fed a low Mg diet for 74 days. A low Mg diet decreased the Mg concentration in the plasma and erythrocytes, which was accompanied by a reduced concentration of eNOs and increased levels of endothelin-1 level in the serum and impaired endothelium-dependent vasodilatation. These effects increased the concentration of proinflammatory molecules, such as VCAM-1, TNF-α, IL-6 and CRP, indicating the development of systemic inflammation and endothelial dysfunction. The increased total NO level, which estimated from the sum of the nitrate and nitrite concentrations in the serum, may also be considered to be a proinflammatory marker. Two weeks of Mg supplementation partially or fully normalised the ability of the vascular wall to effect adequate endothelium-dependent vasodilatation and reversed the levels of most endothelial dysfunction and inflammatory markers (except CRP) to the mean values of the control group. Mg sulphate had the smallest effect on the endothelin-1, TNF-α and VCAM-1 levels. Mg N-acetyltaurate was significantly more effective in restoring the level of eNOS compared to all other studied compounds, except for Mg oxybutyrate. Taken together, the present findings demonstrate that all Mg compounds equally alleviate endothelial dysfunction and inflammation caused by Mg deficiency. Mg sulphate tended to be the least effective compound.

Mechanisms of cataractogenesis in the presence of magnesium deficiency.

Senile cataract is the most common cause of bilateral blindness and results from the loss of transparency of the lens. Maintenance of the unique tissue architecture of the lens is vital for keeping the lens transparent. Membrane transport mechanisms utilizing several magnesium (Mg)-dependent ATPases, play an important role in maintaining lens homeostasis. Therefore, in Mg-deficiency states, ATPase dysfunctions lead to intracellular depletion of K(+) and accumulation of Na(+) and Ca(2+). High intracellular Ca(2+) causes activation of the enzyme calpain II, which leads to the denaturation of crystallin, the soluble lens protein required for maintaining the transparency of the lens. Mg deficiency also interferes with ATPase functions by causing cellular ATP depletion. Furthermore, Mg deficiency enhances lenticular oxidative stress by increased production of free radicals and depletion of antioxidant defenses. Therefore, Mg supplementation may be of therapeutic value in preventing the onset and progression of cataracts in conditions associated with Mg deficiency.

Effects of magnesium taurate on the onset and progression of galactose-induced experimental cataract: in vivo and in vitro evaluation.

Cataract, a leading cause of blindness, is characterized by lenticular opacities resulting from denaturation of lens proteins due to activation of calcium-dependent enzyme, calpain. Magnesium (Mg(2+)) plays an important role not only in maintaining a low lenticular calcium (Ca(2+)) and sodium concentration but also in preserving the lens redox status. Taurine has also been shown to reduce lenticular oxidative stress. Present study evaluated the anticataract effects of magnesium taurate in vivo and in vitro. Among the five groups of 9 Sprague Dawley rats each, two groups received 30% galactose diet with topical (GDMT) or oral treatment (GDMO) with magnesium taurate. Two groups received 30% galactose diet with topical (GDT) or oral vehicle (GDO). Remaining 1 group received normal diet (ND). Weekly slit lamp examination was done during 21 days experimental period and then all rats were sacrificed; Ca/Mg ratio and antioxidant parameters including reduced glutathione (GSH), catalase and superoxide dismutase (SOD) activities were measured in the isolated lenses using ELISA. In the in vitro study, 2 groups of 10 normal rat lenses were incubated in Dulbecco's Modified Eagle's Medium (DMEM) with galactose while 1 similar group was incubated in DMEM without galactose. In one of the groups, galactose containing medium was supplemented with magnesium taurate. After 48 h of incubation, lenses were photographed and Ca(2+)/Mg(2+) ratio and antioxidant parameters were measured as for in vivo study. The in vivo study, at the end of experimental period, demonstrated delay in the development of cataract with a mean opacity index of 0.53 ± 0.04 and 0.51 ± 0.03 in GDMO (p < 0.05 versus GDO) and GDMT (p < 0.01 versus GDT) respectively. Histopathological grading showed a lower mean value in treated groups, however, the differences from corresponding controls were not significant. Lenticular Ca(2+)/Mg(2+) ratio with a mean value of 1.20 ± 0.26 and 1.05 ± 0.26 in GDMO and GDMT was significantly lower than corresponding controls (p < 0.05) and in GDMT no significant difference was observed from ND. Lenticular GSH and catalase activities were significantly lower and SOD activity was significantly higher in all galactose fed groups. However, in GDMT, GSH and catalase were significantly higher than corresponding control with mean values of 0.96 ± 0.30 µmol/gm lens weight and 56.98 ± 9.86 µmol/g lens protein respectively (p < 0.05 for GSH and p < 0.01 for catalase). SOD activity with mean values of 13.05 ± 6.35 and 13.27 ± 7.61 units/mg lens protein in GDMO and GDMT respectively was significantly lower compared to corresponding controls (p < 0.05) signifying lesser upregulation of SOD due to lesser oxidative stress in treated groups. In the in vitro study, lenses incubated in magnesium taurate containing medium showed less opacity and a lower mean Ca(2+)/Mg(2+) ratio of 1.64 ± 0.03, which was not significantly different from lenses incubated in DMEM without galactose. Lens GSH and catalase activities were restored to normal in lenses incubated in magnesium taurate containing medium. Both in vivo and in vitro studies demonstrated that treatment with magnesium taurate delays the onset and progression of cataract in galactose fed rats by restoring the lens Ca(2+)/Mg(2+) ratio and lens redox status.

Effect of magnesium chloride on psychomotor activity, emotional status, and acute behavioural responses to clonidine, d-amphetamine, arecoline, nicotine, apomorphine, and L-5-hydroxytryptophan.

BACKGROUND: The beneficial effects of magnesium (Mg) salts on central manifestations of Mg deficiency are well known. Mg replacement therapy can be effective to prevent some of the serious depression-like and anxiety-related behaviour sequelae of Mg deficiency. However, few experimental studies have been undertaken on Mg-deficiency-induced behavioural changes. Even fewer studies have been carried out on acute behavioural responses to clonidine, D-amphetamine, arecoline, nicotine, apomorphine, and L-5-hydroxytryptophan (HTP), which might characterize possible neuromediator changes in Mg deficiency. The effects of correcting Mg deficiency by magnesium chloride (MgCl2 · 6H2O) and the combination of this salt with vitamin B6, on the behavioural manifestations of Mg deficiency have never been described as well. OBJECTIVE: The aims of this study were: to estimate effect of MgCl2 · 6H2O alone and in combination with vitamin B6 on acute behavioural responses to agonists or blockers of the main neurotransmitter systems in CNS, psychomotor activity and emotional status of rats fed with Mg-deficient diet for 49 days. In our study open field test has shown that in Mg-deficient rats locomotor activity and vertical activity, number of visiting and residence time in central squares were decreased significantly. In the elevated plus maze test, the number of visiting open arms and residence time of rats were significantly less as compared with the control group. In the forced swimming test, time immobile was significantly increased by 44.29% and time of swimming was decreased by 52.79% compared to control. RESULTS: In our study Mg-deficient rats were more sensitive to d-amphetamine-induced motor stereotypes. Mg deficiency antagonized 5-hydroxytryptophan-induced head-twitch response and arecoline-induced tremor. Supplement of MgCl2 · 6H2O with vitamin B6 administered to a Mg-deficient rat increased the Mg level in plasma and erythrocytes. Furthermore, this increase was in relation to vitamin B6 given to the animal. Mg supplementation alone and in combination with pyridoxine normalized acute behavioural responses to d-amphetamine, 5-hydroxytryptophan, and arecoline in Mg deficient rats with a return to pre-deficient levels observed in the Mg sufficient group. DISCUSSION: Combination of Mg salts and pyridoxine hydrochloride can be effective at treating some behavior form of primary Mg deficiency.

Effect of magnesium supplementation containing mineral bishofit (MgCl2 x 6H2O) solution and pyridoxine hydrochloride on erythrocyte magnesium depletion and behaviour of rats after three-month alcoholization.

In therapy it is known that the combination of vitamin B6 and magnesium is beneficial in the treatment of several forms of primary magnesium deficiency. The purpose of the present study was to investigate the effect of complex magnesium supplementation containing mineral bishofit solution (MgCl2 x 6H2O) and pyridoxine hydrochloride on behavioural and biochemical parameters of magnesium-deficient alcoholic rats. A complex magnesium supplementation containing mineral bishofit solution and pyridoxine hydrochloride led both to restoration of magnesium level, and to some correction of behavioural disturbances of animals during chronic alcoholization.