In vitro plasma protein binding and aqueous aggregation behavior of astaxanthin dilysinate tetrahydrochloride

Efficient delivery of carotenoids to adipocytes with albumin

Carotenoids are very effectively delivered by albumin to adipocytes. The uptake of carotenoids to the cells occurs in the form of self-aggregates that localize in the vicinity of the adipocyte membrane, as shown by high spatial resolution Raman spectroscopy. The binding of carotenoids to albumin and the mechanism of their transport were elucidated with the help of chiroptical spectroscopies, in tandem with molecular docking and molecular dynamics simulations. In particular, apart from the recognized high affinity pocket of albumin that binds a carotenoid monomer in domain I, we have identified a hydrophobic periphery area in domain IIIB that loosely bounds the self-aggregated carotenoid in aqueous media and enables its easy detachment in hydrophobic environments. This explains the effectiveness of albumins as nanocarriers of carotenoids to adipocytes in vitro.

The effect of aging on the antioxidative activity of astaxanthin in human aqueous humor

We previously evaluated the antioxidative effects of astaxanthin intake in the aqueous humor by measuring reactive oxygen species-related parameters, including O₂ ^•- scavenging activity, H₂O₂ level, and total hydroperoxides level. In this study, we analyzed the antioxidative effects of astaxanthin in relation to age in 16 males and 19 females (average age 71.3 and 70.6, respectively) who underwent bilateral cataract surgery on one side before and the other side after astaxanthin intake (6 mg/day for 2 weeks). None of the parameters correlated with age before astaxanthin intake, but only total hydroperoxides level was significantly correlated after the astaxanthin intake (r = 0.4, p<0.05). Total hydroperoxides levels were similar in younger and older patients (<70 vs ≥70 years) before astaxanthin, but decreased significantly more in younger patients (-0.21 ± 0.18 vs -0.05 ± 0.31, p<0.05) after the intake, resulting in significantly different levels (p<0.05). The previously observed decrease in mean total hydroperoxides levels following astaxanthin intake was therefore considered likely to be attributable to a greater response in younger subjects. Given that total hydroperoxides levels reflect general antioxidative status, astaxanthin intake may exert a greater antioxidative effect in younger patients. Further comparative studies involving younger subjects and different astaxanthin doses are needed.

Hydrophilic Astaxanthin: PEGylated Astaxanthin Fights Diabetes by Enhancing the Solubility and Oral Absorbability

To develop hydrophilic astaxanthin with significantly enhanced solubility and stability, astaxanthin polyethylene glycol succinate (APGS) was synthesized by esterification of an astaxanthin succinate diester with polyethylene glycol 1000. The chemical structure of the hydrophilic derivative was confirmed by ¹H nuclear magnetic resonance and mass spectra. APGS showed better solubility than free astaxanthin in water and enhanced bioavailability compared to that of free astaxanthin. Additionally, testing the effects on diabetes and inflammation in a high-fat- and high-sucrose-diet-induced insulin-resistant mouse model demonstrated its benefits, suggesting that APGS maintains the health-promoting properties of astaxanthin. These results suggest that APGS could be a better source of hydrophilic astaxanthin.

Aggregation of Fucoxanthin and Its Effects on Binding and Delivery Properties of Whey Proteins

In this study, aggregation of fucoxanthin (FX) and its effects on binding and delivery properties of whey proteins were explored. Initially, the H- and J-aggregates of FX were successfully prepared by adjusting the water/ethanol ratio and water-dripping rate. The transition from J- to H-aggregates was observed over the standing time. Then, the molecular arrangement of FX H-aggregates was analyzed using the point-dipole approximation model and molecular dynamics, showing that their intermolecular distance and angle were about 5.0-6.7 Å and -35° to 35°, respectively. The transformation of J- to H-aggregates was also observed during molecular dynamics, with a shortened intermolecular distance, a reduced solvent accessible surface area, an enhanced interaction force, and a narrowed dihedral angle. Further, the interactions of whey proteins with different forms of FX were investigated, indicating that both β-lactoglobulin and whey protein isolates could form complexes with the monomers, H-aggregates, and J-aggregates of FX. In terms of affinity, whey proteins bound FX monomers more strongly than aggregates. Furthermore, the complexes comprising whey proteins and monomeric FX had better delivery capabilities than aggregated FX, manifested in encapsulation efficiency, physical stability, and bioaccessibility.

Effects of astaxanthin on VEGF level and antioxidation in human aqueous humor: difference by sex

In our previous report, we showed the effect of astaxanthin intake on VEGF level in the aqueous humor and the relationship between VEGF level and reactive oxygen species-related parameters and other relevant factors. VEGF level is associated with total hydroperoxide level, and a multivariate analysis identified sex as a secondary factor affecting these relationships. Here, we analyzed the effects of astaxanthin on the relationship between VEGF level and reactive oxygen species-related parameters by sex. Patients (16 males and 19 females, aged 71.3 and 70.6, respectively) underwent bilateral cataract surgery on one side before and the other side after astaxanthin treatment (6 mg/day for 2 weeks). Levels of VEGF, hydrogen peroxide, and total hydroperoxide, and O₂ ^•- scavenging activity, were measured in the aqueous humor. In females only, VEGF level was negatively correlated with O₂ ^•- scavenging activity before the astaxanthin intake (r = -0.6, p<0.01) and positively correlated with total hydroperoxide level before and after the astaxanthin intake (r = 0.7 and 0.8, respectively, p<0.01). In conclusion, astaxanthin appears to affect O₂ ^•- scavenging activity in the aqueous humor in females, and is likely to be involved in the control of VEGF levels in the anterior eye.

Effects of astaxanthin on antioxidation in human aqueous humor

We evaluated the antioxidative effects of astaxanthin through the changes in superoxide scavenging activity, levels of hydrogen peroxide and total hydroperoxides in human aqueous humor. The study subjects were 35 patients who underwent bilateral cataract surgery on one side before and the other side after intake of astaxanthin (6 mg/day for 2 weeks). Their aqueous humor was taken during the surgery and subjected to measurements of the three parameters. After astaxanthin intake, the superoxide scavenging activity was significantly (p<0.05) elevated, while the level of total hydroperoxides was significantly (p<0.05) lowered. There was a significant negative correlation between the superoxide scavenging activity and the level of total hydroperoxides (r = −0.485, p<0.01), but no correlations between the hydrogen peroxide level and the other two parameters. Astaxanthin intake clearly enhanced the superoxide scavenging activity and suppressed the total hydroperoxides production in human aqueous humor, indicating the possibility that astaxanthin has suppressive effects on various oxidative stress-related diseases.

Hydrophilic carotenoids: recent progress

Carotenoids are substantially hydrophobic antioxidants. Hydrophobicity is this context is rather a disadvantage, because their utilization in medicine as antioxidants or in food chemistry as colorants would require some water dispersibility for their effective uptake or use in many other ways. In the past 15 years several attempts were made to synthetize partially hydrophilic carotenoids. This review compiles the recently synthetized hydrophilic carotenoid derivatives.

Electron- and energy-transfer properties of hydrophilic carotenoids

The antioxidant activities-expressed as the electron-donating properties-of five hydrophilic carotenoids (carotenoid surfactants) and three related hydrophobic carotenoids were investigated by flash photolysis. The electron-transfer rates of the carotenoids to the triplet state of the sensitizer 2-nitronaphthalene and the energy transfer rates of triplet 2-nitronaphthalene to the carotenoids were determined. The results demonstrate that the electron-donating effects of the hydrophilic and hydrophobic carotenoids were comparable when evaluated in acetonitrile. In the presence of water, however, electron transfer (i.e., antioxidant efficiency) was enhanced by a factor of four for the hydrophilic carotenoids. The increased hydrophilicity of carotenoids, therefore, could expand their antioxidant properties, thus facilitating their use as aqueous-phase radical scavengers. At the same time, it was shown that supramolecular assembly ("aggregation") of the amphiphilic carotenoids prevented electron transfer, thus deactivating the antioxidant function. Modulation of the biophysical properties of carotenoids through synthetic modification is capable of increasing the biological and medical utility of this natural class of predominantly hydrophobic antioxidant compound.

Association studies of aggregated aqueous lutein diphosphate with human serum albumin and α1-acid glycoprotein in vitro: Evidence from circular dichroism and electronic absorption spectroscopy

Water-dispersible C40 carotenoid derivatives, with increased utility in mammalian therapeutic applications, include natural stereoisomer-based (3R,3'R,6'R)-lutein (beta,epsilon-carotene-3,3'-diol) derivatives. Esterification with inorganic phosphate and conversion to the sodium salt produced compounds (lutein diphosphate sodium salt; 'LdP') capable of forming red-orange aqueous suspensions after addition to USP-purified water. The aqueous dispersibility of this diphosphate salt reached 29 mg/mL without the addition of heat, detergents, co-solvents, or other additives, and was a potent direct scavenger of superoxide anion (by EPR spectroscopy) in an isolated human neutrophil assay. In the current study, preliminary evidence of the aqueous aggregation of this compound in EPR studies was confirmed using circular dichroism (CD) and electronic absorption (UV-vis) spectroscopy. Evidence for H-type ('card-pack') and J-type ('head-to-tail') self-assemblies was obtained. In vitro analysis of the potential binding interaction between LdP and human serum albumin (HSA) and alpha1-acid glycoprotein (AGP) revealed only non-specific binding with HSA (and none with AGP), contrasting with previous reports of direct interaction between astaxanthin-based soft drugs and the major plasma protein albumin. The rapid in vivo cleavage of this phosphodiester by promiscuous mammalian phosphatases may overcome the aqueous aggregation of the formulated compound. This difference in potential plasma protein interaction with prior reports reflects the subtle structural differences inherent in either the parent carotenoid scaffolds and/or the esterifying moieties.

Disodium disuccinate astaxanthin (Cardax): antioxidant and antiinflammatory cardioprotection

Disodium disuccinate astaxanthin (Cardax), DDA) has cardioprotective effects in the rat, rabbit, and canine models of experimental infarction. It is highly effective by parenteral administration in subchronic and acute dosing regimens. Unpublished data in rats suggest that oral cardioprotection is also readily achievable. DDA-induced myocardial salvage in the canine can reach 100% with a 4-day subchronic dosing regimen. At a single i.v. dose DDA is cardioprotective, when given 2 h before experimental coronary occlusion, but the protection is on the average two-thirds of that achieved with the subchronic regimen in dogs. In conscious animals DDA has no effects on hemodynamic parameters. The primary mechanism of cardioprotection appears to be antioxidant activity involving direct scavenging of superoxide anion, the lynchpin radical in ischemia-reperfusion injury. In addition, modulation of serum complement activity, as well as the reduction in the levels of C-reactive protein (CRP) and the membrane attack complex (MAC) in infarcted tissue suggest a significant antiinflammatory component in the mechanism of cardioprotective action of DDA. Stoichiometric binding of the meso-form of the compound to human serum albumin (HSA) has been demonstrated in vitro. This binding capacity overcomes the supramolecular assembly of the compound in aqueous solution, which by itself improves the stability and shelf life of aqueous formulations. Non-esterified astaxanthin readily enters cardiac tissue after either oral or parenteral administration, providing a reservoir of a cardioprotective agent with a significant half-life due to favorable ADME in mammals. Due to the well-documented safety profile of non-esterified astaxanthin in humans, disodium disuccinate astaxanthin may well find clinical utility in cardiovascular indications in humans following successful completion of preclinical and clinical pharmacology and toxicology studies.

The effects of oral Cardax (disodium disuccinate astaxanthin) on multiple independent oxidative stress markers in a mouse peritoneal inflammation model: influence on 5-lipoxygenase in vitro and in vivo

Disodium disuccinate astaxanthin ('rac'-dAST; Cardax) is a water-dispersible C40 carotenoid derivative under development for oral and parenteral administration for cardioprotection of the at-risk ischemic cardiovascular patient. In experimental infarction models in animals (rats, rabbits, and dogs), significant myocardial salvage has been obtained, up to 100% at the appropriate dose in dogs. The documented mechanism of action in vitro includes direct scavenging of biologically produced superoxide anion; in vivo in rabbits, modulation of the complement activity of serum has also been shown. A direct correlation between administration of the test compound in animals and reductions of multiple, independent markers of oxidative stress in serum was recently obtained in a rat experimental infarction model. For the current study, it was hypothesized that oral Cardax administration would inhibit oxidative damage of multiple relevant biological targets in a representative, well-characterized murine peritoneal inflammation model. A previously developed mass spectrometry-based (LC/ESI/MS/MS) approach was used to interrogate multiple distinct pathways of oxidation in a black mouse (C57/BL6) model system. In vivo markers of oxidant stress from peritoneal lavage samples (supernatants) were evaluated in mice on day eight (8) after treatment with either Cardax or vehicle (lipophilic emulsion without drug) orally by gavage at 500 mg/kg once per day for seven (7) days at five (5) time points: (1) baseline prior to treatment (t=0); (2) 16 h following intraperitoneal (i.p.) injection with thioglycollate to elicit a neutrophilic infiltrate; (3) 4 h following i.p. injection of yeast cell wall (zymosan; t=16 h/4 h thioglycollate+zymosan); (4) 72 h following i.p. injection with thioglycollate to elicit monocyte/macrophage infiltration; and (5) 72 h/4 h thioglycollate+zymosan. A statistically significant sparing effect on the arachidonic acid (AA) and linoleic acid (LA) substrates was observed at time points two and five. When normalized to the concentration of the oxidative substrates, statistically significant reductions of 8-isoprostane-F(2alpha) (8-iso-F(2alpha)) at time point three (maximal neutrophil recruitment/activation), and 5-HETE, 5-oxo-EET, 11-HETE, 9-HODE, and PGF(2alpha) at time point five (maximal monocyte/macrophage recruitment/activation) were observed. Subsequently, the direct interaction of the optically inactive stereoisomer of Cardax (meso-dAST) with human 5-lipoxygenase (5-LOX) was evaluated in vitro with circular dichroism (CD) and electronic absorption (UV/Vis) spectroscopy, and subsequent molecular docking calculations were made using mammalian 15-LOX as a surrogate (for which XRC data has been reported). The results suggested that the meso-compound was capable of interaction with, and binding to, the solvent-exposed surface of the enzyme. These preliminary studies provide the foundation for more detailed evaluation of the therapeutic effects of this compound on the 5-LOX enzyme, important in chronic diseases such as atherosclerosis, asthma, and prostate cancer in humans.

The synthesis and aqueous superoxide anion scavenging of water-dispersible lutein esters

Xanthophyll carotenoids of the C40 series, which includes commercially important compounds such as lutein, zeaxanthin, and astaxanthin, have poor aqueous solubility in the native state. Hawaii Biotech, Inc. (HBI) and others have shown that the aqueous dispersibility of derivatized carotenoids can be increased by varying the chemical structure of the esterified moieties. In the current study, the published series of novel, highly water-dispersible C40 carotenoid derivatives has been extended to include (3R,3'R,6'R)-lutein (beta,epsilon-carotene-3,3'-diol) derivatives. Two novel derivatives were synthesized by esterification with inorganic phosphate and succinic acid, respectively, and subsequently converted to the sodium salts. Red-orange, clear, aqueous suspensions were obtained after addition of these novel derivatives to USP-purified water. Aqueous dispersibility of the disuccinate sodium salt of lutein was 2.85 mg/mL; the diphosphate salt demonstrated a >10-fold increase in dispersibility at 29.27 mg/mL. As reported previously, these aqueous suspensions were obtained without the addition of heat, detergents, co-solvents, or other additives. The direct aqueous superoxide scavenging abilities of these novel derivatives were subsequently evaluated by electron paramagnetic resonance (EPR) spectroscopy in a well-characterized in vitro isolated human neutrophil assay. The novel derivatives were nearly identical aqueous-phase scavengers, demonstrating dose-dependent suppression of the superoxide anion signal (as detected by spin-trap adducts of DEPMPO) in the millimolar range. These lutein-based soft drugs will likely find utility in those commercial and clinical applications for which aqueous-phase singlet oxygen quenching and direct radical scavenging may be required.

Stability, pKa and plasma protein binding of roscovitine

In the present investigation, the binding of roscovitine (100, 500 and 1500 ng/mL) to plasma proteins was studied at 25 and 37 degrees C by ultrafiltration and equilibrium dialysis methods. Drug stability in plasma was assessed during a 48 h at 4, 25 and 37 degrees C. The effect of thawing and freezing on drug stability was studied. The pKa of roscovitine was measured using capillary electrophoresis coupled with mass spectrometry. Roscovitine was quantified utilizing liquid chromatography and tandem mass spectrometry. Roscovitine is highly bound to plasma proteins (90%). Binding of roscovitine to human serum albumin was constant (about 90%) within concentration range studied while the binding to alpha1-acid glycoprotein decreased with increasing drug concentration indicating that albumin is more important in clinical settings. However, alpha1-acid glycoprotein might be important when plasma proteins change with disease. Protein binding was higher at 25 degrees C compared to 37 degrees C. The results obtained by equilibrium dialysis were in good agreement with those obtained by ultrafiltration. Roscovitine was stable at all temperatures studied during 48 h. Roscovitine has a pKa of 4.4 showing that the drug mainly acts like a weak mono-base. The results obtained in our studies are important prior to clinical trials and to perform pharmacokinetic studies.

Analysis of Binding Interaction between the Natural Apocarotenoid Bixin and Human Serum Albumin by Circular Dichroism and Fluorescence Spectroscopy

Bixin is an important, pharmacologically active dietary cis-carotenoid, but its interaction with potential macromolecular targets is completely unexplored. This work was aimed to study the binding of bixin to human serum albumin (HSA), the most abundant protein in blood plasma. Circular dichroism (CD) spectroscopy in combination with UV/VIS absorption spectroscopy and fluorescence quenching techniques were applied. Appearance of induced CD bands in the UV- and VIS-absorption spectral regions indicated the formation of non-covalent carotenoid-albumin complexes. Shape and spectral position of the extrinsic Cotton effects suggested the binding of a single bixin molecule to HSA in chiral conformation. Scatchard and non-linear regression analyses of CD titration data resulted in similar values for the association constant (Ka = 6.6 and 4.6x10(5) M(-1), resp.) and for the number of binding sites (n = 1). The binding interaction was independently confirmed by fluorescence-quenching experiment from which the binding parameters were also calculated. CD Displacement measurements performed with marker ligands established that the main drug binding sites of HSA are not involved in binding of bixin. Palmitic acid decreased the amplitude of the induced CD bands suggesting a common albumin binding site for bixin and long-chain fatty acids. The above data indicate that HSA plays a significant role in the plasma transportation of bixin and related dietary carboxylic acid carotenoids.