Stereoselective mu- and delta-opioid receptor-related antinociception and binding with (+)-thebaine

Natural product modulators of human sensations and mood: molecular mechanisms and therapeutic potential

Humans perceive physical information about the surrounding environment through their senses. This physical information is registered by a collection of highly evolved and finely tuned molecular sensory receptors. A multitude of bioactive, structurally diverse ligands have evolved in nature that bind these molecular receptors. The complex, dynamic interactions between the ligands and the receptors lead to changes in our sensory perception or mood. Here, we review our current knowledge of natural products and their derived analogues that interact specifically with human G protein-coupled receptors, ion channels, and nuclear hormone receptors to modulate the sensations of taste, smell, temperature, pain, and itch, as well as mood and its associated behaviour. We discuss the molecular and structural mechanisms underlying such interactions and highlight cases where subtle differences in natural product chemistry produce drastic changes in functional outcome. We also discuss cases where a single compound triggers complex sensory or behavioural changes in humans through multiple mechanistic targets. Finally, we comment on the therapeutic potential of the reviewed area of research and draw attention to recent technological developments in genomics, metabolomics, and metabolic engineering that allow us to tap the medicinal properties of natural product chemistry without taxing nature.

Herbal medicinal oils in traditional Persian medicine

CONTEXT

In Iran, conventional production methods of herbal oils are widely used by local practitioners. Administration of oils is rooted in traditional knowledge with a history of more than 3000 years. Scientific evaluation of these historical documents can be valuable for finding new potential use in current medicine.

OBJECTIVE

The current study (i) compiled an inventory of herbal oils used in ancient and medieval Persia and (ii) compared the preparation methods and therapeutic applications of ancient times to current findings of medicinal properties in the same plant species.

MATERIALS AND METHODS

Information on oils, preparation methods and related clinical administration was obtained from ancient Persian documents and selected manuscripts describing traditional Persian medicine. Moreover, we investigated the efficacy of medicinal plant species used for herbal oils through a search of the PubMed, Scopus and Google Scholar databases.

RESULTS

In Iran, the application of medicinal oils date back to ancient times. In medieval Persian documents, 51 medicinal oils produced from 31 plant species, along with specific preparation methods, were identified. Flowers, fruits and leaves were most often used. Herbal oils have been traditionally administered via oral, topical and nasal routes for gastrointestinal, musculoskeletal, and neural diseases, respectively. According to current investigations, most of the cited medicinal plant species were used for their anti-inflammatory and analgesic properties.

CONCLUSIONS

Medicinal oils are currently available in Iranian medicinal plant markets and are prepared using traditional procedures for desirable clinical outcomes. Other than historical clarification, the present study provides data on clinical applications of the oils that should lead to future opportunities to investigate their potential medicinal use.

Treating epilepsy in Italy between XIX and XX century

Epilepsy is a neurological disorder which has been recognized since antiquity. This paper evaluates the prophylactic and therapeutic remedies used by folk medicine to cure epilepsy in Italy. The data has been collected by reviewing written sources of physicians, ethnographers, folklorists between the late nineteenth and mid twentieth century. This approach leads to unearthing of 78 heterogeneous healing methods that have been divided into 16 (20%) magical, 20 (26%) religious and 42 (54%) natural remedies. The latter has been subdivided into 18 (43%) animal remedies, 17 (40%) plant remedies and 7 (17%) other remedies. Religious and magical remedies were used with the conviction that they would be able to provide recovery from epilepsy and to ward off evil spirits which had taken possession of the sick. Interestingly, the herbal remedies highlighted 12 (70%) plants that play or might play an important role with respect to the mechanisms that generate the epileptic seizures. This leads us to reconsider the historical significance of folk medicine, too often it is underestimated owing to its use of ineffective remedies, born of incompetence and superstition.

Cycloaddition Reaction of Ethyl Thioxoacetate and the Dienamine Derived from Pummerer's Ketone

The objective of this work is to study the regio- and stereochemistry of the cycloadducts obtained from the treatment of ethyl thioxoacetate and the dienamine derived from Pummerer's ketone.

Study on the activation of the opioid receptors by a set of morphine derivatives in a well-defined assay system

As a first step in our search for new opiates, we have established cellular assays to monitor opioid receptor activation and study the activities of a set of morphine derivatives. Intracellular calcium changes were monitored in human embryonic kidney-293 T cells expressing individual opioid receptors upon cotransfection with a chimeric G protein. This assay was validated by comparing the potencies of the endogenous peptides to reported values. All of the opiates were found to interact with the three opioid receptor subtypes but with a range of differences in efficacies and potencies. Most of the opiates preferentially acted at the μ receptor. None of the opiates showed a preference for the δ receptor. Only oripavine and its precursor thebaine showed a preference for the κ over the μ receptor. The results indicate that the opiates with a C-3 hydroxyl group or C-6 ketone group but in the presence of a 7, 8-single bond exhibit higher activity. It is noteworthy that the 6-O-methyl group seems to improve the selectivity for κ receptor. This is the first comparative and comprehensive report on the activation of the three different opioid receptors by a set of morphine derivatives in a well-defined assay system. These data can serve as a basis for the characterization of novel opiates.

Live cell monitoring of mu-opioid receptor-mediated G-protein activation reveals strong biological activity of close morphine biosynthetic precursors

G-protein activation by receptors is generally measured using (35)S-GTPgammaS binding assays in cell membranes and cannot be well assessed in intact cells. We have recently developed a fluorescence resonance energy transfer (FRET)-based approach to monitor G(i)-protein activation in living cells. Here we report that this technique can be used to determine structure-activity relationships of receptor agonists in intact cells. We have recently shown that morphine is biosynthesized de novo by mammals via a multistep pathway different from that in plants. However, the pharmacological properties of morphine precursors are poorly understood. Here, we directly monitored mu-opioid receptor (MOR)-mediated G(i)-protein activation in living cells by FRET and validated this method with classical GTPgammaS binding assays. Receptor binding studies and FRET measurements demonstrated that several (R)-configurated morphine precursors such as (R)-reticuline, salutaridine, salutaridinol, thebaine, and codeine were partial MOR agonists. Some closer precursors such as oripavine, codeinone, and morphinone activated G(i)-proteins as strongly as morphine, but with slightly lower potencies. The more distant the precursors were positioned in the pathway with respect to morphine, the less efficient and potent they were at MOR. Comparison of pharmacological properties of close morphine precursors and concentrations in which they occur in animal tissues suggests that they might activate MOR signaling under physiological conditions. Taken together, our data indicate that FRET-based assays of G-protein activation can serve to determine the abilities of compounds to activate G-protein signaling directly and in living cells.

N-(trifluoromethyl)benzyl substituted N-normetazocines and N-norketobemidones

To further investigate the unusual profile of N-benzyl substituted opioids, N-trifluoromethylbenzyl normetazocines and norketobemidones were prepared. The introduction of trifluoromethyl substituents on the benzyl group of the (-)-metazocines reduced affinity at all three receptors, with the greatest loss at kappa receptors. Surprisingly, some of the (+)-normetazocines actually possessed higher affinity than the corresponding (-)-isomers. In the ketobemidone series, the effects were different-the 4-trifluoromethyl substituted ketobemidone actually possessed 3-fold higher mu affinity than the unsubstituted parent to give a ligand with good mu affinity. In functional in vitro assays, this compound was a weak antagonists, but in apparent contradiction it was inactive in in vivo assays.