The synthesis and conformation of β-cyclodextrins functionalized with enantiomers of Boc-carnosine

The Therapeutic Potential of Novel Carnosine Formulations: Perspectives for Drug Development

Carnosine (beta-alanyl-L-histidine) is an endogenous dipeptide synthesized via the activity of the ATP-dependent enzyme carnosine synthetase 1 and can be found at a very high concentration in tissues with a high metabolic rate, including muscles (up to 20 mM) and brain (up to 5 mM). Because of its well-demonstrated multimodal pharmacodynamic profile, which includes anti-aggregant, antioxidant, and anti-inflammatory activities, as well as its ability to modulate the energy metabolism status in immune cells, this dipeptide has been investigated in numerous experimental models of diseases, including Alzheimer's disease, and at a clinical level. The main limit for the therapeutic use of carnosine is related to its rapid hydrolysis exerted by carnosinases, especially at the plasma level, reason why the development of new strategies, including the chemical modification of carnosine or its vehiculation into innovative drug delivery systems (DDS), aiming at increasing its bioavailability and/or at facilitating the site-specific transport to different tissues, is of utmost importance. In the present review, after a description of carnosine structure, biological activities, administration routes, and metabolism, we focused on different DDS, including vesicular systems and metallic nanoparticles, as well as on possible chemical derivatization strategies related to carnosine. In particular, a basic description of the DDS employed or the derivatization/conjugation applied to obtain carnosine formulations, followed by the possible mechanism of action, is given. To the best of our knowledge, this is the first review that includes all the new formulations of carnosine (DDS and derivatives), allowing a decrease or complete prevention of the hydrolysis of this dipeptide exerted by carnosinases, the simultaneous blood-brain barrier crossing, the maintenance or enhancement of carnosine biological activity, and the site-specific transport to different tissues, which then offers perspectives for the development of new drugs.

Unveiling the Hidden Therapeutic Potential of Carnosine, a Molecule with a Multimodal Mechanism of Action: A Position Paper

Carnosine (β-alanyl-L-histidine) is a naturally occurring endogenous dipeptide and an over-the-counter food supplement with a well-demonstrated multimodal mechanism of action that includes the detoxification of reactive oxygen and nitrogen species, the down-regulation of the production of pro-inflammatory mediators, the inhibition of aberrant protein formation, and the modulation of cells in the peripheral (macrophages) and brain (microglia) immune systems. Since its discovery more than 100 years ago, a plethora of in vivo preclinical studies have been carried out; however, there is still substantial heterogeneity regarding the route of administration, the dosage, the duration of the treatment, and the animal model selected, underlining the urgent need for "coordinated/aligned" preclinical studies laying the foundations for well-defined future clinical trials. The main aim of the present position paper is to critically and concisely consider these key points and open a discussion on the possible "alignment" for future studies, with the goal of validating the full therapeutic potential of this intriguing molecule.

Improving Cognition with Nutraceuticals Targeting TGF-β1 Signaling

Rescue of cognitive function represents an unmet need in the treatment of neurodegenerative disorders such as Alzheimer’s disease (AD). Nutraceuticals deliver a concentrated form of a presumed bioactive(s) agent(s) that can improve cognitive function alone or in combination with current approved drugs for the treatment of cognitive disorders. Nutraceuticals include different natural compounds such as flavonoids and their subclasses (flavan-3-ols, catechins, anthocyanins, and flavonols), omega-3, and carnosine that can improve synaptic plasticity and rescue cognitive deficits through multiple molecular mechanisms. A deficit of transforming growth factor-β1 (TGF-β1) pathway is an early event in the pathophysiology of cognitive impairment in different neuropsychiatric disorders, from depression to AD. In the present review, we provide evidence that different nutraceuticals, such as Hypericum perforatum (hypericin and hyperforin), flavonoids such as hesperidin, omega-3, and carnosine, can target TGF-β1 signaling and increase TGF-β1 production in the central nervous system as well as cognitive function. The bioavailability of these nutraceuticals, in particular carnosine, can be significantly improved with novel formulations (nanoparticulate systems, nanoliposomes) that increase the efficacy and stability of this peptide. Overall, these studies suggest that the synergism between nutraceuticals targeting the TGF-β1 pathway and current approved drugs might represent a novel pharmacological approach for reverting cognitive deficits in AD patients.

Design of cyclodextrin-based systems for intervention execution

Technologies for nucleic acid delivery have displayed high practical potential in mediating genetic manipulation to modulate metabolic pathways to combat aging. In the previous chapter, we have delineated a series of techniques for designing and developing polymeric vectors as nonviral carriers. Based on what we have discussed, this chapter will introduce how the delivery performance and versatility of polymeric vectors can be further enhanced by using cyclodextrins (CDs). Over the years, CDs have shown promising application potential in different areas, ranging from controlled drug release to chiral separation of basic drugs. These applications are largely mediated by the ability of CDs to undergo host–guest inclusion complexation. Upon incorporation of CDs into the design of a polymeric vector, not only can the flexibility of the design be increased, but the development of a multifunctional carrier for genetic manipulation can also be facilitated.

Multitarget trehalose-carnosine conjugates inhibit Aβ aggregation, tune copper(II) activity and decrease acrolein toxicity

Increasing evidence is accumulating, showing that neurodegenerative disorders are somehow associated with the toxicity of amyloid aggregates, metal ion dyshomeostasis as well as with products generated by oxidative stress. Within the biological oxidation products, acrolein does have a prominent role. A promising strategy to deal with the above neurogenerative disorders is to use multi-functions bio-molecules. Herein, we show how a class of bio-conjugates takes advantage of the antiaggregating, antioxidant and antiglycating properties of trehalose and carnosine. Their ability to sequester acrolein and to inhibit both self- and metal-induced aggregation is here reported. The copper(II) coordination properties of a new trehalose-carnosine conjugate and the relative antioxidant effects have also been investigated.

Selectively functionalized cyclodextrins and their metal complexes

Cyclodextrins (CDs) are cyclic oligomers of alpha-1,4-linked D-glucopyranose. Due to their unique structure, marked by a chiral and hydrophobic cavity, CDs have been extensively used as chiral selectors and drug delivery systems. The functionalization both improve the CD applications and widen their use in many other fields, such as molecular recognition and enzyme mimicking. Moreover, the functionalization highly increases the metal binding properties of the CDs. This critical review is a report of recent applications concerning the CD derivatives and their metal complexes. The metal ion assists the host-guest interaction often increasing the properties of CDs to act as chiral receptors. Furthermore, it can act as a catalytic center in the mimicking of metalloenzymes based on functionalized CDs (164 references).

New glycosidic derivatives of histidine-containing dipeptides with antioxidant properties and resistant to carnosinase activity

Synthesis, antioxidant properties and resistance to carnosinase hydrolysis of histidine-containing dipeptides are reported in this study. Carnosine (beta-alanyl-l-histidine), homocarnosine (gamma-aminobutyryl-l-histidine) and anserine (beta-alanyl-3-methyl-l-histidine) were covalently derivatized with beta-cyclodextrin to form different OH- or NH-bound conjugates. Mass spectroscopic and (1)H NMR data were used to determine the structure and the purity of the various beta-cyclodextrin derivatives. The inhibitory effect towards oxidation of human LDL induced by Cu(2+) ions, was estimated by measuring malondialdehyde formation as a function of increasing concentrations of these newly synthesized compounds (the beta-cyclodextrin-anserine conjugated in 3 had the highest antioxidant effect). All derivatives had higher antioxidant effects than those of the corresponding free histidine-containing dipeptides. Resistance to rat brain carnosinase hydrolysis of the most active derivatives indicated that these compounds are good candidates for further studies in more complex cellular and animal models. Their possible applications for remedies in neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases, are discussed.

Synthesis and antioxidant activity of new homocarnosine beta-cyclodextrin conjugates

Several in vitro and in vivo studies have suggested that carnosine (beta-alanil-L-histidine) and homocarnosine (beta-aminobutyril-L-histidine) can act as scavengers of reactive oxygen species. beta-Cyclodextrin was functionalized with homocarnosine, obtaining the following new bioconjugate isomers: 6(A)-[(4-{[(1S)-1-carboxy-2-(1H-imidazol-4-yl)ethyl]amino}-4-oxobutyl)amino]-6(A)-deoxy-beta-cyclodextrin and (2(A)S,3(A)R)-3A-[(4-{[(1S)-1-carboxy-2-(1H-imidazol-4-yl)ethyl]amino}-4-oxobutyl)amino]-3(A)-deoxy-beta-cyclodextrin. Pulse radiolysis investigations show that the beta-cyclodextrin homocarnosine bioconjugates are scavengers of (*)OH radicals because of the formation of stable imidazole-centered radicals and the scavenger ability of glucose molecules of the macrocycle. The ability of these new beta-cyclodextrin derivatives to inhibit the copper(II) driven LDL oxidation was determined in comparison with that displayed by the analogous carnosine derivatives. Both the beta-cyclodextrin carnosine isomers show a higher protective effect than that of free dipeptide and homocarnosine derivatives, bringing into light the role of the beta-CD cavity. The ability of these new beta-cyclodextrin derivatives to inhibit the copper(II) driven LDL oxidation was determined in comparison with that displayed by the analogous carnosine derivatives. Both the beta-cyclodextrin carnosine isomers show a higher protective effect than that of free dipeptide and homocarnosine derivatives, bringing into light the role of the beta-CD cavity.

Synthesis of 6-mono-6-deoxy-beta-cyclodextrins substituted with isomeric aminobenzoic acids. Structural characterization, conformational preferences, and self-inclusion as studied by NMR spectroscopy in aqueous solution and by X-ray crystallography in the solid state

The synthesis, purification, and characterization of mono-6-modified-beta-cyclodextrins bearing N-attached o-, m-, and p-aminobenzoic acids (2, 3, and 4, respectively) are presented. The structures in aqueous solution were investigated using one- and two-dimensional NMR spectroscopy. Detailed assignment of the spectra together with intramolecular NOE correlations revealed the way each of the isomeric appendages is positioned relative to the macrocyclic cavity. No self-inclusion is observed. The o-isomer 2 turns inward over the top of the primary side and interacts with specific protons of the substituted glucopyranose unit A and those of a neighboring unit. The m-isomer 3 displays two conformations, where the substituent resides above the primary side in a tilted manner and interacts either with the previous or the next unit. We propose that the carboxyl groups in both 2 and 3 are localized through H-bonding with one or two, respectively, primary hydroxyl groups of the neighboring glucopyranose units. In a similar positioning of the aromatic ring of the p-isomer 4, the hydrophilic carboxyl end is fully exposed to the aqueous environment. The X-ray structure of 4 shows that the solution conformation has evolved such that in the crystalline state, the aromatic moiety is inserted through its carboxyl part inside another CD where it establishes intermolecular H-bonds with inward-turned primary OH groups. Besides this stabilization, 4 forms parallel and antiparallel supramolecular chains in the crystal that are additionally stabilized by direct H-bonds.