Alejandro C. Paladini

Possible anxiolytic effects of chrysin, a central benzodiazepine receptor ligand isolated from Passiflora Coerulea

The pharmacological effects of 5,7-dihydroxyflavone (chrysin), a naturally occurring monoflavonoid that displaces [3H]flunitrazepam binding to the central benzodiazepine (BDZ) receptors, were examined in mice. In the elevated plus-maze test of anxiety, diazepam (DZ, 0.3-0.6 mg/kg) or chrysin (1 mg/kg) induced increases in the number of entries into the open arms and in the time spent on the open arms, consistent with an anxiolytic action of both compounds. The effects of chrysin on the elevated plus-maze was abolished by pretreatment with the specific BDZ receptor antagonist Ro 15-1788 (3 mg/kg). In the holeboard, diazepam (1 mg/kg) and chrysin (3 mg/kg) increased the time spent head-dipping. In contrast, high doses of DZ (6 mg/kg) but not of chrysin produced a decrease in the number of head dips and in the time spent head-dipping. In the horizontal wire test, diazepam (6 mg/kg) had a myorelaxant action. In contrast, chrysin (0.6-30 mg/kg) produced no effects in this test. These data suggest that chrysin possesses anxiolytic actions without inducing sedation and muscle relaxation. We postulate that this natural monoflavonoid is a partial agonist of the central BDZ receptors.

Overview—Flavonoids: A New Family of Benzodiazepine Receptor Ligands

Benzodiazepines (BDZs) are the most widely prescribed class of psychoactive drugs in current therapeutic use, despite the important unwanted side-effects that they produce such as sedation, myorelaxation, ataxia, amnesia, ethanol and barbiturate potentiation and tolerance. Searching for safer BDZ-receptor (BDZ-R) ligands we have recently demonstrated the existence of a new family of ligands which have a flavonoid structure. First isolated from plants used as tranquilizers in folkloric medicine, some natural flavonoids have shown to possess a selective and relatively mild affinity for BDZ-Rs and a pharmacological profile compatible with a partial agonistic action. In a logical extension of this discovery various synthetic derivatives of those compounds, such as 6,3′-dinitroflavone were found to have a very potent anxiolytic effect not associated with myorelaxant, amnestic or sedative actions. This dinitro compound, in particular, exhibits a high affinity for the BDZ-Rs (Ki = 12–30 nM). Due to their selective pharmacological profile and low intrinsic efficacy at the BDZ-Rs, flavonoid derivatives, such as those described, could represent an improved therapeutic tool in the treatment of anxiety. In addition, several flavone derivatives may provide important leads for the development of potent and selective BDZ-Rs ligands.

6-Methylapigenin and hesperidin: new valeriana flavonoids with activity on the CNS

Valerian is an ancient tranquillizing drug obtained from the underground organs of several Valeriana species. Its active principles were assumed to be terpenoids in the form of valepotriates and/or as components of the essential oil. However, unknown active compounds were not discarded and synergic effects were suspected. We have recently isolated 6-methylapigenin (MA) from Valeriana wallichii and proved that it is a benzodiazepine binding site (BDZ-bs) ligand [Planta Med. 68 (2002) 934]. The present paper is the first report of the presence of 2S(-)-hesperidin in valeriana and describes that it has sedative and sleep-enhancing properties. MA, in turn, was found to have anxiolytic properties and was able to potentiate the sleep-enhancing properties of hesperidin (HN).MA and HN are new members of the growing family of natural flavonoids with activity on the CNS, and their properties suggest that they are promising drug leads in the field.

GABA(A)-receptor ligands of flavonoid structure.

This review describes the new research developments that have established the CNS-activity of some natural flavonoids. The properties of flavone, chrysin, apigenin and cirsiliol are described and a survey of the occurrence of ligands for the benzodiazepine binding site in the flavonoid field is attempted. Natural compounds, structurally related to flavonoids and with similar CNS-activities, are also included. A medicinal chemistry approach to improve the biochemical and pharmacological properties of the flavone nucleus is described alongside with the enumeration of the principal achievements obtained to date. Quantitative structure-activity relationships studies leading to the formulation of pharmacophore models presumably describing the characteristics of the flavone-binding site in the GABA(A)-receptor are summarized.

SEDATIVE AND SLEEP-ENHANCING PROPERTIES OF LINARIN, A FLAVONOID-ISOLATED FROM VALERIANA OFFICINALIS

We have recently reported the presence of the anxiolytic flavone 6-methylapigenin (MA) and of the sedative and sleep-enhancing flavanone glycoside 2S (-) hesperidin (HN) in Valeriana officinalis and Valeriana wallichii. MA, in turn, was able to potentiate the sleep-inducing properties of HN. The present paper reports the identification in V. officinalis of the flavone glycoside linarin (LN) and the discovery that it has, like HN, sedative and sleep-enhancing properties that are potentiated by simultaneous administration of valerenic acid (VA). These effects should be taken into account when considering the pharmacological actions of valeriana extracts.

Presence of benzodiazepine-like molecules in mammalian brain and milk

From bovine cerebral cortex extracts, used to isolate n-butyl beta carboline-3-carboxylate (8), fractions active in displacing [3H] flunitrazepam binding were purified and shown to contain benzodiazepine-like molecules. These were recognized by UV spectra, retention time in HPLC, and interaction with a specific monoclonal antibody. Such molecules were localized in synaptic vesicles and cytosol of synaptosomes. Similar molecules were also found in cow milk. The possible dietary origin of these benzodiazepine-like molecules is discussed.

The intriguing nature of the multiple actions of growth hormone

Abstract The biological activity of growth hormone is expressed by multiple biochemical effects directly or indirectly related with body growth. There is experimental evidence that several of these effects are produced by different parts of the molecule. How these active centers produce the corresponding physiological effects is still an unsolved problem.

Sequence of thirteen amino acids in the C-terminal end of bovine growth hormone and localization of a disulflde bridge☆

Abstract The carbamidomethyl derivative of reduced bovine growth hormone (BGH) was extensively attacked by carboxypeptidases A and B, and approximately 19 moles of various amino acids was liberated. The correct sequence of 13 amino acids could be established by selective cleavage of the methionyl bonds in the molecule and isolation of a C-terminal dodecapeptide by filtration through Sephadex G-25. The structure of this peptide was studied by carboxypeptidase A attack, Edman degradation, and further study of the fragments obtained by chymotryptic digestion. A disulfide bond connecting the two half-cystines in the dodecapeptide was discovered by the comparative study of the peptides released by the action of cyanogen bromide on native or reduced and blocked hormone. The structure of the C-terminal end in BGH is:

Automatic amino acid analysis: reagent and instrumental improvements.

Abstract A procedure for the automatic analysis of amino acids using the Auto-Analyzer apparatus in combination with a modified Rosen reagent is described. With the use of a narrow column (0.6 cm i.d.) it is possible to estimate 0.03 μmole of a single amino acid with a standard deviation not higher than 5%. Amounts ten times less than the above lower limit can be detected.

Hesperidin, a flavonoid glycoside with sedative effect, decreases brain pERK1/2 levels in mice

The aim of this work was to evaluate if the intraperitoneal administration of the natural compound hesperidin, in a sedative dose, and neo-hesperidin, a hesperidin structural analog that exerts minor sedative effect, were able to induce changes in intracellular signaling cascades in different areas of the brain. The systemic administration of hesperidin produced a marked reduction in the phosphorylation state of extracellular signal-regulated kinases 1/2 (ERK 1/2), but not of Ca(+2)/calmodulin-dependent protein kinase II alpha subunit (alphaCaMKII), in the cerebral cortex, cerebellum and hippocampus. In contrast, neo-hesperidin did not markedly affect the activity of ERK 1/2 in both the cortex and the cerebellum. Taken together, these results demonstrated that intracellular signalling involving a selective decrease in ERK1/2 activation accompanied the depressant action of hesperidin. Even more, the low sedative action of neo-hesperidin correlates with a negligible decrease in phosphorylation state of ERK 1/2 (pERK 1/2), suggesting that low levels of pERK 1/2 in CNS could be a marker of sedative efficacy of flavonoids.