Host-guest complexes of carotenoids with beta-glycyrrhizic acid

Effects of carotenoids on mitochondrial dysfunction

Oxidative stress, an imbalance between pro-oxidant and antioxidant status, favouring the pro-oxidant state is a result of increased production of reactive oxygen species (ROS) or inadequate antioxidant protection. ROS are produced through several mechanisms in cells including during mitochondrial oxidative phosphorylation. Increased mitochondrial-derived ROS are associated with mitochondrial dysfunction, an early event in age-related diseases such as Alzheimer's diseases (ADs) and in metabolic disorders including diabetes. AD post-mortem investigations of affected brain regions have shown the accumulation of oxidative damage to macromolecules, and oxidative stress has been considered an important contributor to disease pathology. An increase in oxidative stress, which leads to increased levels of superoxide, hydrogen peroxide and other ROS in a potentially vicious cycle is both causative and a consequence of mitochondrial dysfunction. Mitochondrial dysfunction may be ameliorated by molecules with antioxidant capacities that accumulate in mitochondria such as carotenoids. However, the role of carotenoids in mitigating mitochondrial dysfunction is not fully understood. A better understanding of the role of antioxidants in mitochondrial function is a promising lead towards the development of novel and effective treatment strategies for age-related diseases. This review evaluates and summarises some of the latest developments and insights into the effects of carotenoids on mitochondrial dysfunction with a focus on the antioxidant properties of carotenoids. The mitochondria-protective role of carotenoids may be key in therapeutic strategies and targeting the mitochondria ROS is emerging in drug development for age-related diseases.

Interpreting the efficacy enhancement mechanism of Chinese medicine processing from a biopharmaceutic perspective

Chinese medicine processing (CMP) is a unique pharmaceutical technology that distinguishes it from natural medicines. Current research primarily focuses on changes in chemical components to understand the mechanisms behind efficacy enhancement in processing. However, this paper presents a novel perspective on the biopharmaceutics of CMP. It provides a comprehensive overview of the current research, emphasizing two crucial aspects: the role of 'heat' during processing and the utilization of processing adjuvants. The paper highlights the generation of easily absorbed components through the hydrolysis of glycosides by 'heat', as well as the facilitation of dissolution, absorption, and targeted distribution of active components through the utilization of processing adjuvants. From a biopharmaceutic perspective, this paper provides a lucid comprehension of the scientific foundation for augmenting the efficacy of CMP. Moreover, it proposes a three-dimensional research framework encompassing chemical reactions, phase transitions, and biopharmaceutical properties to further investigate the mechanisms involved in enhancing the efficacy of CMP.

The Endless World of Carotenoids-Structural, Chemical and Biological Aspects of Some Rare Carotenoids

Carotenoids are a large and diverse group of compounds that have been shown to have a wide range of potential health benefits. While some carotenoids have been extensively studied, many others have not received as much attention. Studying the physicochemical properties of carotenoids using electron paramagnetic resonance (EPR) and density functional theory (DFT) helped us understand their chemical structure and how they interact with other molecules in different environments. Ultimately, this can provide insights into their potential biological activity and how they might be used to promote health. In particular, some rare carotenoids, such as sioxanthin, siphonaxanthin and crocin, that are described here contain more functional groups than the conventional carotenoids, or have similar groups but with some situated outside of the rings, such as sapronaxanthin, myxol, deinoxanthin and sarcinaxanthin. By careful design or self-assembly, these rare carotenoids can form multiple H-bonds and coordination bonds in host molecules. The stability, oxidation potentials and antioxidant activity of the carotenoids can be improved in host molecules, and the photo-oxidation efficiency of the carotenoids can also be controlled. The photostability of the carotenoids can be increased if the carotenoids are embedded in a nonpolar environment when no bonds are formed. In addition, the application of nanosized supramolecular systems for carotenoid delivery can improve the stability and biological activity of rare carotenoids.

Improving the Treatment Effect of Carotenoids on Alzheimer's Disease through Various Nano-Delivery Systems

Natural bioactive compounds have recently emerged as a current strategy for Alzheimer's disease treatment. Carotenoids, including astaxanthin, lycopene, lutein, fucoxanthin, crocin and others are natural pigments and antioxidants, and can be used to treat a variety of diseases, including Alzheimer's disease. However, carotenoids, as oil-soluble substances with additional unsaturated groups, suffer from low solubility, poor stability and poor bioavailability. Therefore, the preparation of various nano-drug delivery systems from carotenoids is a current measure to achieve efficient application of carotenoids. Different carotenoid delivery systems can improve the solubility, stability, permeability and bioavailability of carotenoids to a certain extent to achieve Alzheimer's disease efficacy. This review summarizes recent data on different carotenoid nano-drug delivery systems for the treatment of Alzheimer's disease, including polymer, lipid, inorganic and hybrid nano-drug delivery systems. These drug delivery systems have been shown to have a beneficial therapeutic effect on Alzheimer's disease to a certain extent.

A Novel Berberine–Glycyrrhizic Acid Complex Formulation Enhanced the Prevention Effect to Doxorubicin-Induced Cardiotoxicity by Pharmacokinetic Modulation of Berberine in Rats

Developing a new drug delivery system is one of the useful approaches to overcome the limited use of berberine (BBR) to enhance its absorption and bioavailability. We prepared a novel berberine–glycyrrhizic acid (BBR–GL) complex formulation to increase the plasma concentration and bioavailability of BBR by improving BBR solubility and lowering the absorption barrier. The complex formulation with BBR and GL in the ratio 1:1 was developed through the self-assembly process and evaluated in vitro. Compared with BBR and BBR/GL physical mixture, the BBR–GL complex showed different characteristics by SEM, DSC, FT-IR, and PXRD measurement. In pharmacokinetic evaluation, the BBR–GL complex significantly increased the plasma concentration of BBR and the major metabolite berberrubine (BBB), with the AUC of BBR elevated to 4.43-folds, while the complex was safe as BBR. Furthermore, doxorubicin (DOX) was used to induce cardiotoxicity. Hematological study, histopathological examinations, electrocardiography (ECG), cardiac secretion measurement, and biochemical index analysis proved that the model of doxorubicin-induced cardiotoxicity (DIC) was conducted successfully. With the AUC of BBR increasing in the BBR–GL complex and the absorbed complex itself, the BBR–GL complex enhanced prevention effect to DIC and exhibited a significant prevention effect to attenuate heart damage. Our findings demonstrated that a novel BBR-loaded BBR–GL complex formulation could increase BBR plasma concentration. Improvement of BBR bioavailability by the BBR–GL complex could coordinate with GL to attenuate DIC. Concerning the safety of the drug delivery system at present, the BBR–GL complex could be a potential therapeutic formulation for the prevention of cardiac damage in the clinical application of doxorubicin.

Supramolecular assemblies based on natural small molecules: Union would be effective

Natural products have been used to prevent and treat human diseases for thousands of years, especially the extensive natural small molecules (NSMs) such as terpenoids, steroids and glycosides. A quantity of studies are confined to concern about their chemical structures and pharmacological activities at the monomolecular level, whereas the spontaneous assemblies of them in liquids yielding supramolecular structures have not been clearly understood deeply. Compared to the macromolecules or synthetic small molecular compounds, NSMs have the inherent advantages of lower toxicity, better biocompatibility, biodegradability and biological activity. Self-assembly of single component and multicomponent co-assembly are unique techniques for designing supramolecular entities. Assemblies are of special significance due to their range of applications in the areas of drug delivery systems, pollutants capture, materials synthesis, etc. The assembled mechanism of supramolecular NSMs which are mainly driven by multiple non-covalent interactions are summarized. Furthermore, a new hypothesis aimed to interpret the integration effects of multi-components of traditional Chinese medicines (TCMs) inspired on the theory of supramolecular assembly is proposed. Generally, this review can enlighten us to achieve the qualitative leap for understanding natural products from monomolecule to supramolecular structures and multi-component interactions, which is valuable for the intensive research and application.

Enhancement of oral bioavailability and anti-hyperuricemic activity of aloe emodin via novel Soluplus®-glycyrrhizic acid mixed micelle system

The objective of this study was to fabricate a novel drug delivery system using Soluplus® (polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer) and glycyrrhizic acid to improve solubility, bioavailability, and anti-hyperuricemic activity of aloe emodin (AE). The AE-loaded mixed micelles (AE-M) were prepared by thin-film hydration method. The optimal AE-M contained small-sized (30.13 ± 1.34 nm) particles with high encapsulation efficiency (m/m, %) of 90.3 ± 1.08%. The release rate of AE increased in the micellar formulation than that of free AE in the four media (DDW, pH 7.0; phosphate buffer solution, pH 7.4; phosphate buffer solution, pH 6.8; and hydrochloric acid aqueous solution, pH 1.2). In comparison to free AE, the pharmacokinetic study of AE-M showed that its relative oral bioavailability increased by 3.09 times, indicating that mixed micelles may promote gastrointestinal absorption. More importantly, AE-M effectively reduced uric acid level by inhibiting xanthine oxidase (XOD) activity in model rats. The degree of ankle swelling, serum levels of interleukin (IL)-1, and IL-6-related inflammatory factors levels all decreased in the gouty arthritis model established via monosodium urate (MSU) crystals. Taken together, the AE-M demonstrated the potential to improve the bioavailability, anti-hyperuricemic activity, and anti-inflammation of AE.

Photostabilization of ketoprofen by inclusion in glycyrrhizin micelles and gel nanoparticles

Ketoprofen (KP) is known to be the most photosensitive among the nonsteroidal anti-inflammatory drugs and may induce phototoxic and photoallergic reactions. Phototoxic side effects of KP are associated with the...

Mechanism of the enhancing effect of glycyrrhizin on nifedipine penetration through a lipid membrane

The saponin glycyrrhizin from liquorice root shows the ability to enhance the therapeutic activity of other drugs when used as a drug delivery system. Due to its amphiphilic properties, glycyrrhizin can form self-associates (dimers, micelles) and supramolecular complexes with a wide range of hydrophobic drugs, which leads to an increase in their solubility, stability and bioavailability. That is why the mechanism of the biological activity of glycyrrhizin is of considerable interest and has been the subject of intensive physical and chemical research in the last decade. Two mechanisms have been proposed to explain the effect of glycyrrhizin on drug bioavailability, namely, the increase in drug solubility in water and enhancement of the membrane permeability. Interest in the membrane-modifying ability of glycyrrhizic acid (GA) is also growing at present due to its recently discovered antiviral activity against SARS-CoV-2 Bailly and Vergoten (2020) [1]. In the present study, the passive permeability of the DOPC lipid membrane for the calcium channel blocker nifedipine was elucidated by parallel artificial membrane permeability assay (PAMPA) and full atomistic molecular dynamics (MD) simulation with free energy calculations. PAMPA experiments show a remarkable increase in the amount of nifedipine (NF) permeated with glycyrrhizin compared to free NF. In previous studies, we have shown using MD techniques that glycyrrhizin molecules can integrate into the lipid bilayer. In this study, MD simulation demonstrates a significant decrease in the energy barrier of NF penetration through the lipid bilayer in the presence of glycyrrhizin both in the pure DOPC membrane and in the membrane with cholesterol. This effect can be explained by the formation of hydrogen bonds between NF and GA in the middle of the bilayer.

Carotenoids: Importance in Daily Life-Insight Gained from EPR and ENDOR

Carotenoids are indispensable molecules for life. They are present everywhere in plants, algae, bacteria whom they protect against free radicals and oxidative stress. Through the consumption of fruits and vegetables and some carotenoid-containing fish, they are introduced into the human body and, similarly, protect it. There are numerous health benefits associated with the consumption of carotenoids. Carotenoids are antioxidants but at the same time they are prone to oxidation themselves. Electron loss from the carotenoid forms a radical cation. Furthermore, proton loss from a radical cation forms a neutral radical. In this mini-review, we discuss carotenoid radicals studied in our groups by various physicochemical methods, namely the radical cations formed by electron transfer and neutral radicals formed by proton loss from the radical cations. They contain many similar hyperfine couplings due to interactions between the electron spin and numerous protons in the carotenoid. Different EPR and ENDOR methods in combination with DFT calculations have been used to distinguish the two independent carotenoid radical species. DFT predicted larger coupling constants for the neutral radical compared to the radical cation. Previously, INDO calculations miss assigned the large couplings to the radical cation. EPR and ENDOR have aided in elucidating the physisorb, electron and proton transfer processes that occur when carotenoids are adsorbed on solid artificial matrices, and predicted similar reactions in aqueous solution or in plants. After years of study of the physicochemical properties of carotenoid radicals, the different published results start to merge together for a better understanding of carotenoid radical species and their implication in biological systems. Up until 2008, the radical chemistry in artificial systems was elucidated but the correlation between quenching ability and neutral radical formation was an inspiration to look for these radical species in vivo. In addition, the EPR spin-trapping technique has been applied to study inclusion complexes of carotenoids with different delivery systems.

Soluble Cyanobacterial Carotenoprotein as a Robust Antioxidant Nanocarrier and Delivery Module

To counteract oxidative stress, antioxidants including carotenoids are highly promising, yet their exploitation is drastically limited by the poor bioavailability and fast photodestruction, whereas current delivery systems are far from being efficient. Here we demonstrate that the recently discovered nanometer-sized water-soluble carotenoprotein from Anabaena sp. PCC 7120 (termed AnaCTDH) transiently interacts with liposomes to efficiently extract carotenoids via carotenoid-mediated homodimerization, yielding violet–purple protein samples. We characterize the spectroscopic properties of the obtained pigment–protein complexes and the thermodynamics of liposome–protein carotenoid transfer and demonstrate the delivery of carotenoid echinenone from AnaCTDH into liposomes with an efficiency of up to 70 ± 3%. Most importantly, we show efficient carotenoid delivery to membranes of mammalian cells, which provides protection from reactive oxygen species (ROS). Incubation of neuroblastoma cell line Tet21N in the presence of 1 μM AnaCTDH binding echinenone decreased antimycin A ROS production by 25% (p < 0.05). The described carotenoprotein may be considered as part of modular systems for the targeted antioxidant delivery.

Antioxidant Activity in Supramolecular Carotenoid Complexes Favored by Nonpolar Environment and Disfavored by Hydrogen Bonding

Carotenoids are well-known antioxidants. They have the ability to quench singlet oxygen and scavenge toxic free radicals preventing or reducing damage to living cells. We have found that carotenoids exhibit scavenging ability towards free radicals that increases nearly exponentially with increasing the carotenoid oxidation potential. With the oxidation potential being an important parameter in predicting antioxidant activity, we focus here on the different factors affecting it. This paper examines how the chain length and donor/acceptor substituents of carotenoids affect their oxidation potentials but, most importantly, presents the recent progress on the effect of polarity of the environment and orientation of the carotenoids on the oxidation potential in supramolecular complexes. The oxidation potential of a carotenoid in a nonpolar environment was found to be higher than in a polar environment. Moreover, in order to increase the photostability of the carotenoids in supramolecular complexes, a nonpolar environment is desired and the formation of hydrogen bonds should be avoided.

Supramolecular Carotenoid Complexes of Enhanced Solubility and Stability-The Way of Bioavailability Improvement

Carotenoids are natural dyes and antioxidants widely used in food processing and in therapeutic formulations. However, their practical application is restricted by their high sensitivity to external factors such as heat, light, oxygen, metal ions and processing conditions, as well as by extremely low water solubility. Various approaches have been developed to overcome these problems. In particular, it was demonstrated that application of supramolecular complexes of “host-guest” type with water-soluble nanoparticles allows minimizing the abovementioned disadvantages. From this point of view, nanoencapsulation of carotenoids is an effective strategy to improve their stability during storage and food processing. Also, nanoencapsulation enhances bioavailability of carotenoids via modulating their release kinetics from the delivery system, influencing the solubility and absorption. In the present paper, we present the state of the art of carotenoid nanoencapsulation and summarize the data obtained during last five years on preparation, analysis and reactivity of carotenoids encapsulated into various nanoparticles. The possible mechanisms of carotenoids bioavailability enhancement by multifunctional delivery systems are also discussed.

Formulation of injectable glycyrrhizic acid-hydroxycamptothecin micelles as new generation of DNA topoisomerase I inhibitor for enhanced antitumor activity

To develop a new drug delivery system is one of the useful approaches to break through the limitation of hydroxycamptothecin (HCPT), a typical DNA topoisomerase I (Topo I) inhibitor in clinical appliance. Injectable glycyrrhizic acid-hydroxycamptothecin (GL-HCPT) micelles that were able to dramatically improve the solubility and stability of HCPT were prepared through self-assembly process and evaluated both in vitro and in vivo. With a mean particle size (PS) of 105.7 ± 9.7 nm and a drug loading (DL) of 9.0 ± 1.5%, GL-HCPT micelles were rapidly internalized by HepG2 cells after 1 h, significantly increasing the intracellular accumulation of HCPT. Compared with the current used HCPT injection and HCPT/GL physical mixture, GL-HCPT micelles showed enhanced antitumor activity against liver cancer cells (HepG2 and Huh7) as well as a superior suppression on the tumor growth of HepG2 tumor bearing mice. Interestingly, GL-HCPT micelles gathered in liver and simultaneously reduced the drug accumulation in normal tissues, thereby exhibiting minimal cytotoxicity to human normal liver cells (LO2). Therefore, we offered a convenient and cost-effective strategy to construct an intravenous drug delivery system (GL-HCPT micelles) as new generation of DNA Topo I inhibitor for enhanced cancer chemotherapy.

Glycyrrhizin-Assisted Transport of Praziquantel Anthelmintic Drug through the Lipid Membrane: An Experiment and MD Simulation

Praziquantel (PZQ) is one of the most widespread anthelmintic drugs. However, the frequent insufficient application of PZQ after oral administration is associated with its low solubility, penetration rate, and bioavailability. In the present study, the permeation of PZQ through a 1,2-dioleoyl- sn-glycero-3-phosphocholine (DOPC) membrane was investigated to probe glycyrrhizin-assisted transport. Glycyrrhizin (or glycyrrhizic acid, GA), a natural saponin, shows the ability to enhance the therapeutic activity of various drugs when it is used as a drug delivery system. However, the molecular mechanism of this effect is still under debate. In the present study, the transport rate was measured experimentally by a parallel artificial membrane permeation assay (PAMPA) and molecular dynamics (MD) simulation with DOPC lipid bilayers. The formation of the noncovalent supramolecular complex of PZQ with disodium salt of GA (Na2GA) in an aqueous solution was proved by the NMR relaxation technique. PAMPA experiments show a strong increase in the amount of the penetrating praziquantel molecules in comparison with a saturated aqueous solution of pure drug used as a control. MD simulation of PZQ penetration through the bilayer demonstrates an increase in permeability into the membrane in the presence of a glycyrrhizin molecule. A decrease in the free energy barrier in the middle of the lipid bilayer was obtained, associated with the hydrogen bond between PZQ and GA. Also, GA reduces the local bilayer surface resistance to penetration of PZQ by rearranging the surface lipid headgroups. This study clarifies the mechanism of increasing the drug's bioavailability in the presence of glycyrrhizin.

Atorvastatin calcium inclusion complexation with polysaccharide arabinogalactan and saponin disodium glycyrrhizate for increasing of solubility and bioavailability

The aim of the present investigation was to enhance the solubility and dissolution of atorvastatin calcium (ATV), a poorly water-soluble drug with larch polysaccharide arabinogalactan (AG) and disodium glycyrrhizate (Na₂GA) as carriers of drug delivery systems for improving its bioavailability. The interactions of ATV with AG or Na₂GA were investigated by DSC, XRD, SEM, and NMR techniques. The molecular weights of supramolecular systems-inclusion complexes and micelles-which are the hosts for ATV molecules were measured. On the other hand, the rapid storage assay (+ 40 °C for 3 months) showed that the chemical stability of ATV/AG and ATV/Na₂GA complexes had been enhanced compared with pure ATV. In vitro drug release showed a significant increase in ATV's dissolution rate after formation of a complex with Na₂GA or AG. Pharmacokinetic tests in vivo on laboratory animals showed a significant increase in ATV's bioavailability after its introduction as a complex with Na₂GA or AG. Moreover, ATV/AG and ATV/Na₂GA complexes showed a more prominent decrease of total cholesterol (TC) level compared to net ATV. Therefore, the novel mechanochemically synthesized complexes of ATV with AG or Na₂GA as drug delivery systems might be potential and promising candidates for hypercholesterolemia treatment and deserved further researches.

Glycyrrhizic acid: A promising carrier material for anticancer therapy

Drug delivery systems have become an integral part of anticancer drugs today. Design of novel drug carriers may lead to significant enhancement in antineoplastic therapy. Glycyrrhizic acid (GL), which is the most important active ingredient extracted from the licorice root shows great potential as a carrier material in this field. Recent studies have indicated that the combination of GL and first-line drugs had better therapeutic effects on cancers. GL showed a series of anti-cancer-related pharmacological activities, such as broad-spectrum anti-cancer ability, resistance to the tissue toxicity caused by chemotherapy and radiation, drug absorption enhancing effects and anti-multidrug resistance (MDR) mechanisms, as a carrier material in drug delivery systems. This review introduced the current research progress on pharmacological mechanisms of GL and development of GL-based drug carriers in anti-cancer field to provide basis for the application prospects of GL. The design of novel GL-based drug delivery systems will bring new opportunities and challenges to anti-cancer therapy.

Self-Association of Glycyrrhizic Acid. NMR Study

The use of various NMR techniques allows to demonstrate the aggregation processes of β-glycyrrhizic acid (GA) in water/methanol (4:1, v:v) mixture with solution pH≤5. The micelle formation was monitored by measuring T2 relaxation and diffusion of GA. The model of gelation from micelles was suggested. It was shown that NMR chemical shifts of the protons of GA glucuronic moiety are sensitive to solution pH and not sensitive to GA concentration changes. At the same time the protons of triterpene moiety are sensitive to the nearest environment during the GA aggregation, and micelles are formed by hydrophobic interaction between the triterpene moieties of GA.

Spectroscopic and molecular dynamics characterization of glycyrrhizin membrane-modifying activity

Glycyrrhizic acid (GA) is a triterpene glycoside extracted from licorice root. Due to its amphiphilicity GA is capable of forming complexes with a variety of hydrophobic molecules, substantially increasing their solubility. GA can enhance the therapeutic effects of various drugs. It was hypothesized that the increased bioavailability of the drug by GA is not only due to increased solubility, but also to enhancement of drug permeability through cell membranes. In this study the interaction of GA with POPC liposomes and model DOPC, POPC and DPPC bilayers was investigated by NMR with addition of shift reagents and MD simulations. This work helps to better understand the mechanism of enhanced drug bioavailability in the presence of GA. NMR and MD reveal that GA does penetrate into the lipid bilayer. NMR shows that GA changes the mobility of lipids. GA is predominantly located in the outer "half-layer" of the liposome and that the middle of the hydrophobic tails is the preferred location. GA freely passes through the bilayer surface to the inner part bringing a few water molecules. Also both approaches indicate pore formation in the presence of GA. The GA interaction with membranes is an additional aspect of the biological activity of GA-based drug delivery systems.

Formulation and evaluation of novel glycyrrhizic acid micelles for transdermal delivery of podophyllotoxin

CONTEXT

As the first-line agent for genital warts, podophyllotoxin (POD) could induce extensively skin burning, itching, and erythema. Meanwhile, as a common anti-inflammatory agent, glycyrrhizic acid (GA), also has amphipathic and solubilizing properties, indicating that it might be a promising drug carrier.

OBJECTIVE

The objective of this study is to formulate and characterize the POD-loaded GA micelles preparation and to evaluate its drug release characteristics and anti-inflammatory properties.

MATERIALS AND METHODS

The novel micelles preparation was prepared by ultrasonic dispersion method and characterized using different scanning calorimetries, dynamic light scattering, and transmission electron microscopies. Subsequently, its encapsulation efficiency (EE), drug-loading content (LC), in vitro skin permeation, in vivo drug retention, and distribution of POD were detected. The anti-inflammatory effect of the preparation was reflected by HE staining and immunohistochemistry in the rat skin.

RESULTS

The POD-loaded GA micelles formed spherical shapes (approximately 10 nm) with an EE of 78.53 ± 2.17% and a LC of 7.293 ± 0.42%. Meaningfully, unlike the extensive distribution of the POD tincture throughout the skin tissue, POD released from the POD-loaded GA micelles mainly located in the epidermis and could maintain steady skin retention for 12 h. Moreover, the POD-loaded GA micelles induced less leukocyte infiltration and inflammatory factors (IL-6 and TNF-α) expression when compared with the POD tincture.

DISCUSSION AND CONCLUSION

Our results suggested that the POD-loaded GA micelles could achieve a higher POD distribution in the epidermal layer as well as a lighter skin inflammation. This new POD delivery system might be a potential and promising candidate for genital warts and deserved further researches.

Water soluble biocompatible vesicles based on polysaccharides and oligosaccharides inclusion complexes for carotenoid delivery

Since carotenoids are highly hydrophobic, air- and light-sensitive hydrocarbon compounds, developing methods for increasing their bioavailability and stability towards irradiation and reactive oxygen species is an important goal. Application of inclusion complexes of "host-guest" type with polysaccharides and oligosaccharides such as arabinogalactan, cyclodextrins and glycyrrhizin minimizes the disadvantages of carotenoids when these compounds are used in food processing (colors and antioxidant capacity) as well as for production of therapeutic formulations. Cyclodextrin complexes which have been used demonstrated enhanced storage stability but suffered from poor solubility. Polysaccharide and oligosaccharide based inclusion complexes play an important role in pharmacology by providing increased solubility and stability of lipophilic drugs. In addition they are used as drug delivery systems to increase absorption rate and bioavailability of the drugs. In this review we summarize the existing data on preparation methods, analysis, and chemical reactivity of carotenoids in inclusion complexes with cyclodextrin, arabinogalactan and glycyrrhizin. It was demonstrated that incorporation of carotenoids into the "host" macromolecule results in significant changes in their physical and chemical properties. In particular, polysaccharide complexes show enhanced photostability of carotenoids in water solutions. A significant decrease in the reactivity towards metal ions and reactive oxygen species in solution was also detected.

Solubilization and stabilization of macular carotenoids by water soluble oligosaccharides and polysaccharides

Xanthophyll carotenoids zeaxanthin and lutein play a special role in the prevention and treatment of visual diseases. These carotenoids are not produced by the human body and must be consumed in the diet. On the other hand, extremely low water solubility of these carotenoids and their instability restrict their practical application as components of food or medicinal formulations. Preparation of supramolecular complexes of zeaxanthin and lutein with glycyrrhizic acid, its disodium salt and the natural polysaccharide arabinogalactan allows one to minimize the aforementioned disadvantages when carotenoids are used in food processing as well as for production of therapeutic formulations with enhanced solubility and stability. In the present study, the formation of supramolecular complexes was investigated by NMR relaxation, surface plasmon resonance (SPR) and optical absorption techniques. The complexes increase carotenoid solubility more than 1000-fold. The kinetics of carotenoid decay in reactions with ozone molecules, hydroperoxyl radicals and metal ions were measured in water and organic solutions, and significant increases in oxidation stability of lutein and zeaxanthin in arabinogalactan and glycyrrhizin complexes were detected.

Photochemical and optical properties of water-soluble xanthophyll antioxidants: aggregation vs complexation

Xanthophyll carotenoids can self-assemble in aqueous solution to form J- and H-type aggregates. This feature significantly changes the photophysical and optical properties of these carotenoids, and has an impact on solar energy conversion and light induced oxidative damage. In this study we have applied EPR and optical absorption spectroscopy to investigate how complexation can affect the aggregation ability of the xanthophyll carotenoids zeaxanthin, lutein, and astaxanthin, their photostability, and antioxidant activity. It was shown that complexation with the polysaccharide arabinogalactan (AG) polymer matrix and the triterpene glycoside glycyrrhizin (GA) dimer reduced the aggregation rate but did not inhibit aggregation completely. Moreover, these complexants form inclusion complexes with both monomer and H-aggregates of carotenoids. H-aggregates of carotenoids exhibit higher photostability in aqueous solutions as compared with monomers, but much lower antioxidant activity. It was found that complexation increases the photostability of both monomers and the aggregates of xanthophyll carotenoids. Also their ability to trap hydroperoxyl radicals increases in the presence of GA as the GA forms a donutlike dimer in which the hydrophobic polyene chain of the xanthophylls and their H-aggregates lies protected within the donut hole, permitting the hydrophilic ends to be exposed to the surroundings.

Improvement of pharmacological values of the nifedipine by means of mechanochemical complexation with glycyrrhizic acid

A new water-soluble form of the calcium blocker nifedipine (NF) with glycyrrhizic acid (GA) (with molecular ratio 1:4) has been obtained by mechanochemical synthesis. Its pharmacological advantages in comparison with nifedipine were determined. An effective dose of nifedipine in complex reduced to 10 times as compared to its therapeutic dose while high antihypertensive activity preservation and pleiotropic antiarhythmic activity enhancement. This new antihypertensive and antiarhythmic agent (complex of NF:GA = 1:4) is chemically stable and safe for parenteral administration.

Properties of zeaxanthin and its radical cation bound to the minor light-harvesting complexes CP24, CP26 and CP29

Nonphotochemical quenching (NPQ) is a fundamental mechanism in photosynthesis by which plants protect themselves against excess excitation energy and which is thus of crucial importance for plant survival and fitness. Recently, carotenoid radical cation (Car(*+)) formation has been discovered to be a key step in the feedback deexcitation quenching component (qE) of NPQ, whose molecular mechanism and location remains elusive. A recent model for qE suggests that the replacement of violaxanthin (Vio) by zeaxanthin (Zea) in photosynthetic pigment binding pockets can in principle result in qE via the so-called "gear-shift" or electron transfer quenching mechanisms. We performed pump-probe measurements on individual antenna complexes of photosystem II (CP24, CP26 and CP29) upon excitation of the chlorophylls (Chl) into their first excited Q(y) state at 660 nm when either Vio or Zea was bound to those complexes. The Chl lifetime was then probed by measuring the decay kinetics of the Chl excited state absorption (ESA) at 900 nm. The charge-transfer quenching mechanism, which is characterized by a spectral signature of the transiently formed Zea radical cation (Zea(*+)) in the near-IR, has also been addressed, both in solution and in light-harvesting complexes of photosystem II (LHC-II). Applying resonant two-photon two-color ionization (R2P2CI) spectroscopy we show here the formation of beta-Car(*+) in solution, which occurs on a femtosecond time-scale by direct electron transfer to the solvent. The beta-Car(*+) maxima strongly depend on the solvent polarity. Moreover, our two-color two-photon spectroscopy on CP29 reveals the spectral position of Zea(*+) in the near-IR region at 980 nm.

Carotenoid radical cations as a probe for the molecular mechanism of nonphotochemical quenching in oxygenic photosynthesis

Nonphotochemical quenching (NPQ) is a fundamental mechanism in photosynthesis which protects plants against excess excitation energy and is of crucial importance for their survival and fitness. Recently, carotenoid radical cation (Car*+) formation has been discovered to be a key step for the feedback deexcitation quenching mechanism (qE), a component of NPQ, of which the molecular mechanism and location is still unknown. We have generated and characterized carotenoid radical cations by means of resonant two color, two photon ionization (R2C2PI) spectroscopy. The Car*+ bands have maxima located at 830 nm (violaxanthin), 880 nm (lutein), 900 nm (zeaxanthin), and 920 nm (beta-carotene). The positions of these maxima depend strongly on solution conditions, the number of conjugated C=C bonds, and molecular structure. Furthermore, R2C2PI measurements on the light-harvesting complex of photosystem II (LHC II) samples with or without zeaxanthin (Zea) reveal the violaxanthin (Vio) radical cation (Vio*+) band at 909 nm and the Zea*+ band at 983 nm. The replacement of Vio by Zea in the light-harvesting complex II (LHC II) has no influence on the Chl excitation lifetime, and by exciting the Chls lowest excited state, no additional rise and decay corresponding to the Car*+ signal observed previously during qE was detected in the spectral range investigated (800-1050 nm). On the basis of our findings, the mechanism of qE involving the simple replacement of Vio with Zea in LHC II needs to be reconsidered.