The ecology and bioactivity of some Greco-Roman medicinal minerals: the case of Melos earth pigments.

Mineral compounds, as pigments and therapeutics, appeared regularly in the technical and medical texts of the Greco-Roman (G-R) world. We have referred to them as 'G-R medicinal minerals' and we suggest that despite their seeming familiarity, there are actually many unknowns regarding their precise nature and/or purported pharmacological attributes. Earth pigments are part of that group. This paper presents a brief overview of our work over the past twenty years relating to: a. the attempt to locate a select number of them in the places of their origin; b. their chemical/mineralogical characterization; c. the study of their ecology via the identification of the microorganisms surrounding them; d. their testing as antibacterials against known pathogens. In the process, and to fulfil the above, we have developed a novel methodological approach which includes a range of analytical techniques used across many disciplines (mineralogy, geochemistry, DNA extraction and microbiology). This paper focuses on a select number of earth pigments deriving from the island of Melos in the SW Aegean, celebrated in antiquity for its Melian Earth, a white pigment, and asks whether they might display antibacterial activity. We demonstrate that some (but not all) yellow, green and black earth pigments do. We also show that the manner in which they were dispensed (as powders or leachates) was equally important. The results, although preliminary, are informative. Given their use since deep time, earth pigments have never lost their relevance. We suggest that the study of their ecology/mineralogy and potential bioactivity allows for a better understanding of how our perception of them, as both pigments and therapeutics, may have evolved.

An investigation into the comparative efficacy of soluble aspirin and solid paracetamol in postoperative pain after third molar surgery.

OBJECTIVE: To compare the efficacy of soluble aspirin 900 mg and paracetamol 1,000 mg in patients with postoperative pain after third molar surgery. DESIGN: A randomised, placebo controlled, double-blind study. SETTING: Day stay units of Oral and Maxillofacial Surgery at Cardiff Dental Hospital and Hexham General Hospital, Northumberland. SUBJECTS AND METHODS: One hundred and sixty-seven (104 female) patients who required the removal of their impacted third molars under general anaesthesia. INTERVENTION: In the early postoperative period, patients were medicated with either a single dose of soluble aspirin 900 mg, solid paracetamol 1,000 mg or placebo. MAIN OUTCOME MEASURES: Pain intensity was measured on 100 mm visual analogue scales at 0, 5, 10, 15, 20, 30, 45, 60, 90, 120 and 240 minutes after dosing. Other efficacy variables evaluated included time to rescue medication and an overall assessment of the study medication efficacy by the patient on completion of the study. RESULTS: One hundred and sixty-seven patients consented to take part in the study, but only 153 were medicated. Of the 14 patients not treated, 10 failed to develop sufficient pain to enter the study, two withdrew consent, one had an adverse reaction to the general anaesthetic and one was a protocol violator. Over the four hour investigation period, patients treated with soluble aspirin reported significantly less pain when compared with those treated with paracetamol (mean difference in AUC(0-240) = -2001, 95% CI -3893 to -109, p=0.038) and placebo (mean difference in AUC(0-240) = -3470, 95% CI -5719 to -1221, p=0.003). Similarly, at 20 and 30 minutes after dosing, patients in the soluble aspirin group were reporting significantly less pain than those in the paracetamol treatment group (mean difference in pain intensity: at 20 minutes -7.9, 95% CI -15.3 to -0.6, p=0.035; at 30 minutes -10.6, 95% CI -18.6 to -2.6, p=0.010). There were no significant differences between treatment groups with respect to the number of patients requiring rescue medication, however the time to dosing was significantly longer for those taking soluble aspirin when compared with placebo (hazard ratio 2.34, 95% CI 1.41 to 3.88, p<0.001). CONCLUSION: The findings from this study showed that soluble aspirin 900 mg provides significant and more rapid analgesia than paracetamol 1,000 mg in the early postoperative period after third molar surgery.

Comparison of the pharmacokinetic profiles of soluble aspirin and solid paracetamol tablets in fed and fasted volunteers.

The aim of this study was to investigate the absorption of popular preparations of two common analgesics--soluble aspirin and solid paracetamol tablets. An open, randomised, crossover study design was used to compare the pharmacokinetic parameters of soluble aspirin and solid paracetamol tablets in 16 healthy, male volunteers from the University of the Witwatersrand, South Africa, in both fed and fasted states. Plasma concentrations of paracetamol, aspirin and salicylic acid were measured. It was found that the rate of absorption was significantly faster for soluble aspirin than for solid paracetamol, regardless of fed or fasting state, considering time to maximum concentration (p < 0.01), time to first quantifiable concentrations (p < 0.05) and absorption rate (p < 0.01). Absorption rate was significantly affected by food for both soluble aspirin (p = 0.028) and for solid paracetamol (p = 0.0003). Time to maximum concentration was not significantly affected by food for soluble aspirin (p = 0.17) but significantly lengthened for solid paracetamol (p = 0.0003). The extent of absorption was affected by food in terms of maximum concentration for both drugs (p = 0.0001), with a reduction of 49% in the fed state for solid paracetamol compared to 18% for soluble aspirin, the difference between the drugs being statistically significant (p = 0.0024). The overall bioavailability of soluble aspirin was unaffected by food and the bioavailability of salicylic acid was increased in the fed state, whereas that of solid paracetamol was lowered in the fed state. Greater inter-individual variation was seen in paracetamol concentrations compared with aspirin or salicylic acid levels. In conclusion, these results show that the absorption of soluble aspirin is largely unaffected by food, whereas, in the same volunteers, the absorption of solid paracetamol tablets is greatly affected. In some volunteers, maximum plasma concentrations of paracetamol following food did not reach levels previously reported to be required for effective analgesia, and this may have implications for pain relief in some individuals. The practice in some individuals of taking aspirin tablets after food to minimise potential gastric disturbance should not affect the level of analgesia.

Use of aspirin in cardiovascular prophylaxis.

The value of prophylatic low-dose aspirin in patients who have experienced a myocardial infarction (MI), stroke or transient ischaemic attack (TIA) has been established beyond all reasonable doubt in a number of major overviews of randomised controlled trials. The value of aspirin in so-called 'primary prevention' is debated, but discussions are based on a misunderstanding. The terms 'primary' and 'secondary' relate to past vascular events and the occurrence of a prior event is only one factor in the estimation of the risk of a future event. Trials have confirmed that patients at high risk, who have not already had a clinical event, do benefit from aspirin. The estimation of risk, and the balancing of this against the chance of undesirable side-effects from aspirin, constitutes a clinical judgement. Although there is only limited evidence from trials, it is reasonable to assume that the earlier aspirin is given in infarction, the greater the benefit is likely to be. This assumption underlies advice from a number of bodies that aspirin should be given by a doctor, nurse or paramedic on first contact with a patient experiencing sudden severe chest pain. Again, although there is no direct evidence from trials, it would seem reasonable to advise patients who have been judged to be at increased risk of infarction to carry aspirin tablets and to chew and swallow one or two immediately if they experience sudden severe chest pain. Aspirin has a fascinating history. The new uses now being suggested, namely in the management of dementia, cancer and other conditions, make it likely that it will have an even more fascinating future.

The influence of dosage form on aspirin kinetics: implications for acute cardiovascular use.

In this study, the pharmacokinetics of several formulations of aspirin were examined: soluble aspirin, mouth-dispersible aspirin, plain aspirin and enteric-coated aspirin granules. Blood samples were taken at frequent intervals for 24 hours after single dosing in 12 healthy volunteers and Tmax, Cmax and t1/2 measured. Cmax was significantly higher for soluble aspirin than for the other formulations and the t1/2 was shorter. The results show the rapid absorption of aspirin from a soluble formulation compared with that from plain aspirin or enteric-coated aspirin granules. Recommendations to treat patients suspected of having a heart attack as soon as possible with aspirin are now widely accepted and the present study would suggest that soluble aspirin should be the aspirin of choice in this situation.

Comparative bioavailability of aspirin and paracetamol following single dose administration of soluble and plain tablets.

In this study, the bioavailability of aspirin and paracetamol was compared in plain and soluble combination formulations in fasting, healthy volunteers. Blood samples were taken and Cmax, Tmax and AUC measured at various times following administration of single doses of the two formulations in 12 subjects. The rapidity of uptake of aspirin following administration of a soluble formulation suggests significant absorption from the stomach. There was no significant difference in the pharmacokinetic parameters of paracetamol derived from a soluble or plain formulation. A comparison of the uptake of aspirin from the soluble aspirin formulation with paracetamol from either plain or soluble tablets showed that aspirin entered the plasma and achieved peak levels significantly more quickly. However, the half life of paracetamol was significantly longer than that of aspirin. These findings suggest that onset of analgesia should be more rapid following dosing with soluble aspirin, a conclusion supported by comparative efficacy studies conducted with differing formulations of aspirin.

Antagonism of the stimulatory effects of efaroxan and glibenclamide in rat pancreatic islets by the imidazoline, RX801080.

1. The imidazoline alpha 2-adrenoceptor antagonist, efaroxan, stimulates insulin secretion from rat isolated islets and antagonizes the ability of diazoxide to inhibit glucose-induced insulin secretion. These effects result from closure of ATP-sensitive potassium channels although the mechanisms involved have not been elucidated. 2. In the present work, we have examined the effects of a close structural analogue of efaroxan, RX801080, in rat isolated islets of Langerhans. RX801080 was found to be ineffective as a stimulator of insulin secretion and did not prevent the inhibition of insulin secretion mediated by diazoxide. 3. RX801080 acted as an antagonist of the actions of several imidazolines (efaroxan, phentolamine and midaglizole) in rat islets. It dose-dependently inhibited the ability of efaroxan to antagonize the effects of diazoxide in islets and also completely inhibited the direct stimulation of insulin secretion mediated by efaroxan. 4. RX801080 also antagonized the effects of the non-imidazoline, ATP-sensitive potassium channel blocker, glibenclamide, in rat islets. It inhibited both the capacity of glibenclamide to stimulate insulin secretion and the ability of glibenclamide to overcome the inhibitory effects of diazoxide in rat islets. 5. Antagonism of glibenclamide responses by RX801080 was not due to inhibition of binding of the sulphonylurea to its receptor on the pancreatic beta-cell. 6. The results suggest that imidazoline compounds and sulphonylureas interact with distinct binding sites on islet cells, but that these sites can interact functionally to control islet cell ATP-sensitive potassium channel activity and insulin secretion.

The alpha 2-adrenoceptor antagonist efaroxan modulates K+ATP channels in insulin-secreting cells.

The actions of efaroxan, a highly selective and potent alpha 2-adrenoceptor antagonist, on insulin secretion, cAMP levels, 86Rb+ efflux and ATP-regulated potassium (K+ATP) channels have been studied using isolated pancreatic islets of Langerhans and RINm5F cells. In the absence of an adrenoceptor agonist, efaroxan (1-100 microM) potentiated glucose-induced secretion over the range 4-10 mM glucose, but was without effect upon the maximal rate of secretion induced by 20 mM glucose. Efaroxan did not affect cAMP levels. Suppression of insulin release by the potassium channel opener diazoxide, was partially alleviated by efaroxan and was associated with an inhibition of the diazoxide-induced increase in the rate of 86Rb+ efflux. Using isolated patches of membrane we found efaroxan to be an effective blocker of K+ATP channels, with a KI value of 12 microM and a Hill coefficient of approximately 1. These data indicate that efaroxan promotes insulin secretion, in the absence of exogenous agonists, by a mechanism that involves inhibition of ATP-regulated K+ channels.

Mechanisms involved in stimulation of insulin secretion by the hypoglycaemic alpha-adrenergic antagonist, DG-5128.

The selective alpha 2-antagonist DG-5128 provoked a dose-dependent stimulation of insulin release from isolated rat islets. DG-5128 was only weakly effective as an antagonist of noradrenaline-induced inhibition of insulin secretion but, surprisingly, was able to reverse the suppression of secretion and increase in 86Rb efflux from preloaded islets, mediated by diazoxide. These effects were not reproduced with more effective alpha-antagonists, suggesting that stimulation of insulin secretion by DG-5128 is independent of alpha-receptor blockade.

Identification of human platelet alpha 2-adrenoceptors with a new antagonist [3H]-RX821002, a 2-methoxy derivative of idazoxan.

1. The binding of a new alpha 2-adrenoceptor antagonist, [3H]-RX821002 (2-(2-methoxy-1,4-benzodioxan-2-yl)-2-imidazoline), was investigated in human platelet membranes and compared with [3H]-yohimbine binding parameters. 2. Analysis of kinetic data revealed association and dissociation time courses consistent with a simple biomolecular reaction. Saturation isotherms showed that [3H]-RX821002 labelled a higher total number of alpha 2-binding sites (224 +/- 31 vs 168 +/- 24 fmol mg-1 protein) than [3H]-yohimbine and with higher affinity (Kd: 0.92 +/- 0.06 vs 1.51 +/- 0.08 nM). Moreover [3H]-RX821002 exhibited a lower percentage of nonspecific binding 3. The difference in total binding is due to a better labelling of the alpha 2-adrenoceptors in the low affinity state by [3H]-RX821002 since the labelled receptors number in high affinity state was identical with the two radioligands. 4. [3H]-RX821002 binding displayed a specificity similar to that obtained with [3H]-yohimbine. The potency of various compounds acting on adrenoceptors was: yohimbine greater than oxymetazoline greater than UK14304 greater than (-)-adrenaline greater than prazosin greater than or equal to (+)-adrenaline greater than isoprenaline. This order of potency is classical for an alpha 2A-adrenoceptor. 5. RX821002 is a more potent alpha 2-adrenoceptor antagonist than yohimbine on adrenaline-induced platelet aggregation. 6. These results indicate that [3H]-RX821002 is a suitable ligand for the identification of human platelet alpha 2-adrenoceptors.

[3H]RX821002: a new tool for the identification of alpha 2A-adrenoceptors.

The human adenocarcinoma cell-line HT29 was used as a model to investigate the binding properties of a new antagonist radioligand of the imidazoline series, [3H]RX821002. All aspects of [3H]RX821002 binding conclusively prove that this radioligand is a valuable tool for labelling alpha 2A-adrenoceptors. [3H]RX821002 binding was very rapid and reversible. Computer-assisted analysis of kinetic data revealed association and dissociation time courses consistent with a simple bimolecular reaction. Saturation isotherms indicated that [3H]RX821002 labeled with high affinity a single population of non-interacting sites displaying a KD of 1.7 +/- 0.1 nM. Adrenoceptor agonists and antagonists inhibited [3H]RX821002 and [3H]yohimbine binding with a strictly similar rank order of potency which is characteristic of alpha 2A-adrenoceptors. The binding parameters of [3H]RX821002 were compared with those of other commercially available [3H]antagonists, [3H]yohimbine and [3H]idazoxan. Analysis of the saturation isotherms for the three radioligands showed that (1) [3H]RX821002 was the radioligand exhibiting the lower percentage of non-specific binding and the better affinity, (2) the Bmax of [3H]RX821002 was significantly higher than that of [3H]yohimbine. The difference in Bmax was not due to better labelling of one of the two affinity states of the receptor but was greatly reduced in glycylglycine buffer, suggesting that, in Tris-Mg2+ buffer, [3H]yohimbine does not label the entire alpha 2-adrenoceptor population.

Heteroaromatic analogues of the alpha 2-adrenoreceptor partial agonist clonidine.

A 1,4-dioxane analogue (1) of the alpha 2-adrenoreceptor partial agonist clonidine (2) has previously been shown to possess an interesting but complex pharmacological profile. In this study, from a series of other heterocyclic analogues of clonidine, the 1,4-oxazines 6 and 12 were found to resemble 1 in that they are partial alpha 2-agonists in the periphery and are excluded from the central nervous system. However, when given directly into the brain, they behave as pure alpha 2-antagonists.

Indoline analogues of idazoxan: potent alpha 2-antagonists and alpha 1-agonists.

The synthesis and alpha-adrenergic activity of a series of substituted 2-imidazolinylindolines are described. Substitution in the indoline ring generated compounds with a spectrum of adrenoceptor antagonist/agonist profiles that proved sensitive to both the nature and position of the substituent. Many of the derivatives possess greater presynaptic antagonist potency than the corresponding benzodioxan 1, dihydrobenzofuran 2, and indan 3 analogues; however, this alpha 2-antagonism is often accompanied by alpha 1-agonist activity. It was not possible to separate alpha 2-antagonist from alpha 1-agonist properties in this series. Compounds of most interest proved to be the N-ethyl 6, 5-chloro-N-methyl 18, and 5-chloro-N-ethyl 23 derivatives, all being potent alpha 2-antagonists and alpha 1-agonists. Substitution at the 4- and 7-position of the indoline ring generally gave compounds with nonselective agonist properties.

Substituted 1,3,4-thiadiazoles with anticonvulsant activity. 4. Amidines.

Two different structural types of 2-aryl-1,3,4-thiadiazole amidines were synthesized and evaluated for anticonvulsant activity. Enhancement of the inherent anticonvulsant activity therein and separation of this activity from the accompanying sedative action of these compounds were attempted. The most potent compounds occurred in the 2-(trifluoromethyl)phenyl series of type 3 amidines, but they also possessed a relatively high level of neurotoxicity and sedation as demonstrated in the rotorod test.

Substituted 1,3,4-thiadiazoles with anticonvulsant activity. 1. Hydrazines.

The synthesis and anticonvulsant activity of a series of 2-aryl-5-hydrazino-1,3,4-thiadiazoles are described. The combination of preferred aromatic substituents in the 2-position coupled with alkyl substitution on the hydrazine moiety led to a number of potent compounds lacking sedation, ataxia, or lethality. 5-(2-Biphenylyl)-2-(1-methylhydrazino)-1,3,4-thiadiazole (4m) represents a new class of anticonvulsant agent and compares favorably with the standard drugs phenytoin, phenobarbital, and carbamazepine.

Substituted 1,3,4-thiadiazoles with anticonvulsant activity. 2. Aminoalkyl derivatives.

This paper describes the synthesis and pharmacological evaluation of a number evaluation of a number of substituted 1,3,4-thiadiazoles. The first member of the series, 2-(aminomethyl)-5-(2-biphenylyl)-1,3,4-thiadiazole (7) was found to possess potent anticonvulsant properties in rats and mice and compared favorably with the standard anticonvulsant drugs phenytoin, phenobarbital, and carbamazepine in a number of test situations. The potency of compound 7 was maintained on alkylation of the side-chain nitrogen atom; however, aryl substitution or chain lengthening caused a drop in potency. Replacement of the 2-biphenylyl group by phenyl or benzyl also lead to inactive compounds.

Alpha-adrenoreceptor reagents. 4. Resolution of some potent selective prejunctional alpha 2-adrenoreceptor antagonists.

The resolution of three 2-substituted derivatives of idazoxan is described. The enantiomers show large separations in activity in a variety of in vitro and in vivo tests, and the active isomers are all potent and selective antagonists at the alpha 2-adrenoreceptor. The significance of these results in relation to those published on the enantiomers of idazoxan and to those on optically active alpha 2-adrenoreceptor agonists is discussed.

Effect of methoxy substitution on the adrenergic activity of three structurally related alpha 2-adrenoreceptor antagonists.

We have recently reported the synthesis and alpha 2-antagonist activity of the methoxy derivative 2 [2-(2-methoxy-1,4-benzodioxan-2-yl)-2-imidazoline] and described the enhanced potency of this compound over the parent 1,4-benzodioxan, idazoxan, in reversing the inhibition caused by alpha 2-adrenoreceptor agonists of the electrically induced twitch in the rat or mouse vas deferens. It was of interest to us to discover whether a similar substitution in the structurally related alpha 2-adrenoreceptor antagonists piperoxan, prosympal, and fenmetazole would similarly enhance potency. We subsequently discovered that this was not so and potency was decreased markedly. In particular, that of the methoxy derivative of piperoxan was ca. 220 times less than the parent structure.

Alpha-adrenoreceptor reagents. 3. Synthesis of some 2-substituted 1,4-benzodioxans as selective presynaptic alpha 2-adrenoreceptor antagonists.

The synthesis and pharmacological activity of a series of 2-substituted derivatives of the selective alpha 2-adrenoreceptor antagonist idazoxan (RX 781094) is described. Substitution in this position by alkyl, alkenyl, cycloalkenyl, and alkoxy groups in many cases gives compounds whose potencies and selectivities are significantly greater than those of the parent compound.