Carrageenan films as promising mucoadhesive ocular drug delivery systems.

Polymer mucoadhesive films being developed for use in ophthalmology represent a new tool for drug delivery and are considered an alternative to traditional dosage forms. Due to their mucoadhesive properties, carrageenans (CRGs) are widely used in various forms for drug delivery. In this study, films based on CRGs of various structural types (κ/ß, κ, x, and λ) for use in ophthalmology were studied. The films were loaded with the active substance echinochrome (ECH), a sea urchin pigment used in ophthalmology. Spectral data showed that ECH remained stable after its incorporation into the CRG films and did not oxidize for at least six months. Hydrophilic CRG films with a thickness of 10-12 µm were characterized in terms of their swelling and mucoadhesive properties. The rheological properties of solutions formed after film dissolution in artificial tears were also assessed. κ- and κ/ß-CRG films with ECH exhibited pseudoplastic behavior after rehydrating films with an artificial tear solution. The CRG-loaded films had different swelling characteristics depending on the structure of the CRG used. The films based on highly sulfated CRGs dissolved in artificial tears, while the films of low-sulfated κ/ß-CRG exhibited limited swelling. All studied ECH-loaded films exhibited mucoadhesive properties, which were evaluated by a texture analyzer using mucous tissue of the small intestine of the pig as a model. There was a slight prolongation of ECH release from CRG films in artificial tears. The effect of CRG/ECH on the epithelial cell lines of the outer shell of the human eye was investigated. At low concentrations, ECH in the composition of the CRG/ECH complex had no cytotoxic effect on corneal epithelial and conjunctival human cells. The use of ECH-containing films can prevent the drug from being immediately washed away by tears and help to retain it by increasing viscosity and having mucoadhesive properties.

Carrageenans and Their Oligosaccharides from Red Seaweeds Ahnfeltiopsis flabelliformis and Mastocarpus pacificus (Phyllophoraceae) and Their Antiproliferative Activity.

Comparative structural analysis of gelling polysaccharides from A. flabelliformis and M. pacificus belonging to Phyllophoraceae and the effect of their structural features and molecular weight on human colon cancer cell lines (HT-29, DLD-1, HCT-116) was carried out. According to chemical analysis, IR and NMR spectroscopies, M. pacificus produces kappa/iota-carrageenan with a predominance of kappa units and minor amounts of mu and/or nu units, while the polysaccharide from A. flabelliformis is iota/kappa-carrageenan (predominance of iota units) and contains negligible amounts of beta- and nu-carrageenans. Iota/kappa- (Afg-OS) and kappa/iota-oligosaccharides (Mp-OS) were obtained from the original polysaccharides through mild acid hydrolysis. The content of more sulfated iota units in Afg-OS (iota/kappa 7:1) was higher than in Mp-OS (1.0:1.8). The poly- and oligosaccharides up to 1 mg/mL did not show a cytotoxic effect on all tested cell lines. Polysaccharides showed an antiproliferative effect only at 1 mg/mL. Oligosaccharides had a more pronounced effect on HT-29 and HCT-116 cells than the original polymers, while HCT-116 cells were slightly more sensitive to their action. Kappa/iota-oligosaccharides exhibit a greater antiproliferative effect and more strongly decrease the number of colonies forming in HCT-116 cells. At the same time, iota/kappa-oligosaccharides inhibit cell migration more strongly. Kappa/iota-oligosaccharides induce apoptosis in the SubG0 and G2/M phases, while iota/kappa-oligosaccharides in the SubG0 phase.

Antiherpetic Activity of Carrageenan Complex with Echinochrome A and Its Liposomal Form.

Herpes simplex virus (HSV) infections, the incidence of which is still widespread throughout the world, are actualizing the search and development of new, more effective antiherpetic drugs. The development of multifunctional drug delivery systems, including liposome-based ones, has become a relevant and attractive concept in nanotechnology. The ability of complexes of κ- and Σ-carrageenans (CRGs)-sulfated polysaccharides of red algae, with echinochrome A (Ech), as well as the liposomal form of the Σ-CRG/Ech complex-to inhibit different stages of HSV-1 infection in Vero cells was studied. By quantum chemical calculations, it was shown that CRG forms stable complexes with Ech. We have shown that complexes of κ-CRG/Ech and Σ-CRG/Ech exhibit highest virucidal activity with a selectivity index (SI) of 270 and 350, respectively, and inhibition of virus-cell interaction (SI of 83 and 32, respectively). The liposomal form of the Σ-CRG/Ech complex after virus adsorption and penetration to cells effectively reduced the HSV-1 plaque formation. The virus-inhibiting activity of the liposomal form of the Σ-CRG/Ech complex was three times higher than that of the Σ-CRG/Ech complex itself. Obtaining CRGs/Ech complexes and their liposomal forms can become the basis of a successful strategy for the development of promising antiherpetic drugs.

Carrageenan gel beads for echinochrome inclusion: Influence of structural features of carrageenan.

Carrageenan (CRG) and carrageenan/chitosan (CH) gel beads (CRG/CH) were prepared as a release delivery system for echinochrome A (Ech). According to spectral data, the Ech was dispersed in the polymer matrix, interacted with CRG, was not oxidised, and remained stable after encapsulation in CRG beads. Carrageenan beads containing Ech were coated with CH by layering. The influence of the structural features of CRG on the formation of beads and the beads morphology, swelling behaviour, mucoadhesive properties and drug release were evaluated. The polysaccharide matrices with Ech showed different swelling characteristics depending on the pH of the medium and the structure of the CRG used. The slow drug release from polysaccharide matrixes was observed for κ- and κ/ß-CRG beads, that contained 3,6-anhydro-α-d-galactopyranose units and had high molecular weight. The obtained results showed the prospects of using polysaccharide beads to include Ech.

Structural characteristics of carrageenans of red alga Mastocarpus pacificus from sea of Japan.

The sulfated polysaccharide from sterile alga Mastocarpus pacificus was investigated. Partial reductive hydrolysis and NMR spectroscopy showed that the extracted polysaccharides were only carrageenans. According to FT-IR- and NMR spectroscopy this polysaccharide was a hybrid kappa/iota-carrageenan with a predominance of kappa-type units. According to MALDI-TOFMS, oligosaccharide fragments obtained by mild acid hydrolysis had a polymerization degree of 1-9, while chains built up of galactose residues were up to 3. Tandem ESI mass spectrometry together with innovative 18O-labelling method showed that the polymer chain of the carrageenan included kappa-carrabiose, kappa-carratetraose, iota-carrabiose, hybrid kappa/iota oligosaccharide units and contained minor insertions of mu-carrageenan (the precursor of kappa-carrageenan). Parallel artificial membrane permeability assay shown that the studied carrageenan inhibited bile salts permeation through an artificial membrane imitating the gastrointestinal barrier by 50 % on average compared to negative control independent of incubation time. However, its action was less pronounced than the hindering ability of cholestyramine.

Mucoadhesive properties of sulphated polysaccharides carrageenans from red seaweed families Gigartinaceae and Tichocarpaceae.

The mucoadhesive properties of different types of carrageenan (kappa-, kappa/beta-, iota/kappa- and lambda-CRGs) isolated from red seaweed families Gigartinaceae and Tichocarpaceae collected on the Pacific coast were studied. We examined the interaction between CRGs and pig stomach mucin in dilute aqueous solutions using a set of methods. Measurements of the dynamic light scattering of mucin in the presence of CRG showed that the polysaccharides cause aggregation of mucin particles, as confirmed by microscopy data. The addition of CRGs to solutions of mucin resulted in the formation of a mixture that changed the charge of mucin, especially in the case of kappa- and kappa/beta-CRGs. The interaction between CRG and porcine gastric mucin in the presence of various additives confirmed that hydrogen bonds and electrostatic interactions are complemented when CRG and mucin are mixed in an aqueous medium, which is also confirmed by in vitro methods based on measurements of work of adhesion and shear stress. Kappa- and kappa/beta-CRGs that contain 3,6-anhydro-α-d-galactopyranose chains (DA) have high molecular weight and exhibit a high density of available hydrogen bonding groups able to interact more strongly with mucin glycoproteins.

Liposomal Form of the Echinochrome-Carrageenan Complex.

Inclusion of drugs in liposomes offers the potential for localized and sustained delivery to mucosal surfaces. The inclusion of the carrageenan matrix with echinochrome A ((Ech)-the active substance of the drug Histochrome) in liposomes was studied. According to the spectral characteristics, Ech was not oxidized and retained stability after encapsulation in the liposomes and the lyophilization process. Loading the liposomes with negatively charged polysaccharide results in the increase in the zeta potential to more negative values (from -14.6 to -24.4 mV), that together with an increasing in the sizes of liposomes (from 125.6 ± 2.5 nm to 159.3 ± 5.8 nm) propose of the formation of the polymer coating on liposomes. The interactions of liposomes with porcine stomach mucin was determined by the DLS and SEM methods. The changes in the zeta-potential and size of the mucin particles were observed as the result of the interaction of liposomes with mucin. To evaluate the mucoadhesive properties of liposomes and the penetration of Ech in the mucosa, a fresh-frozen inner surface of the small intestine of a pig as a model of mucous tissue was used. Polysaccharide-coated liposomes exhibit very good mucoadhesive properties -50% of Ech remains on the mucosa.

Carrageenans-Sulfated Polysaccharides from Red Seaweeds as Matrices for the Inclusion of Echinochrome.

The possibility of using different types of carrageenans (CRG) as matrixes for incorporating of echinochrome A (Ech) was investigated. Ech interacts with carrageenans and is incorporated into the macromolecular structure of the polysaccharide. The inclusion of Ech in carrageenan matrices decreased its oxidative degradation and improved its solubility. The changing in the charge and morphology of CRGs during binding with Ech was observed. The rate of Ech release from CRG matrices depended on the structure of the used polysaccharide and the presence of specific ions. The gastroprotective effect of CRG/Ech complexes was investigated on the model of stomach ulcers induced by indomethacin in rats. Complexes of CRG/Ech exhibited significant gastroprotective activity that exceeded the activity of the reference drug Phosphalugel. The gastroprotective effect of the complexes can be associated with their protective layer on the surface of the mucous membrane of a stomach.

Structural analysis and cytokine-induced activity of gelling sulfated polysaccharide from the cystocarpic plants of Ahnfeltiopsis flabelliformis.

Gelling sulfated polysaccharide from the cystocarpic plants of Ahnfeltiopsis flabelliformis was studied. According to FT-IR and NMR spectroscopy data, the polysaccharide was found to be iota/kappa-carrageenan with iota- and kappa-type units in a 2:1 ratio containing beta-carrageenan units and minor amounts of nu- and mu-carrageenans. The HPLC and ESI MS/MS data of enzymatic hydrolysis products revealed that the main components of the polymer chain are iota-carrabiose, iota-carratetraose and hybrid tetra- and hexasaccharides consisting of kappa- and iota-units. Xylose was a substituent of a hydroxyl group at C-6 of 1,3-linked ß-d-galactose in the total polysaccharides. It was shown that the ability of carrageenans to increase the synthesis of cytokines depended on their molecular weight. The polysaccharide induced the synthesis of the anti-inflammatory cytokine IL-10, whereas oligosaccharides increased the synthesis of both pro- and anti-inflammatory cytokines at high concentrations.

Absolute Configuration and Body Part Distribution of the Alkaloid 6-epi-Monanchorin from the Marine Polychaete Chaetopterus variopedatus.

As a result of the first study on secondary metabolites from the cosmopolitan bioluminescent marine tube polychaete Chaetopterus variopedatus, a new bicyclic guanidine alkaloid, 6-epi-monanchorin (1), along with the previously known monanchorin (2) were isolated. The structure of 1 was elucidated by spectroscopic and chemical methods, including a cleavage of the C1-07 bond to obtain a secondary alcohol (3), which was used to determine the absolute configurations by Mosher's method. It was found that 1 and 2 were mainly accumulated in a secreted mucus special organ of the worm (food net), where green and blue-green microalgae were detected. A biosynthetic pathway to 6-epi-monanchorin and monanchorin from dietary polyeic fatty acid precursors was proposed.

Structural peculiarities of polysaccharide from sterile form of Far Eastern red alga Ahnfeltiopsis flabelliformis.

KCl-insoluble sulfated polysaccharide from sterile alga Ahnfeltiopsis flabelliformis was investigated. Partial reductive hydrolysis and NMR spectroscopy showed that the polysaccharide comprises disaccharide units of carrabiose only. According to FT-IR-, 1D, 2D NMR spectroscopies and mass-spectrometry this polysaccharide is kappa/beta-carrageenan with ratio of kappa- and beta-types units 3:1 and contains minor amounts of iota- and gamma-carrageenans (precursor of beta-carrageenan). In addition, ESIMS/MS data suggested that xylose (minor amount) is present in the polysaccharide as a substituent one of hydroxyl group of galactose. According to aPTT and PT assays the studied carrageenan affected mostly intrinsic pathway of coagulation, while it effect on the extrinsic pathway is absent.

Total synthesis of hybocarpone, a cytotoxic naphthazarin derivative from the lichen Lecanora hybocarpa, and related compounds.

The concise synthesis of the lichen-derived antitumor agent hybocarpone (1) and its analogs is described. A new synthetic approach is based on the direct oxidative dimerization of the available naphthazarin precursors in the formation of the binaphtho[2,3-b; 2,3-d]furantetraone structure. It was shown that the first step to tetrahydrofuran features is the bridging hindered S*,S* and R*,S* carbon-carbon bonds of the molecules, setting the relative configurations of the 5aS*,6aS*,12aS*,12bS* and 5aS*,6aR*,12aR*,12bS* diastereomers.

Echinamines A and B, first aminated hydroxynaphthazarins from the sea urchin Scaphechinus mirabilis.

Two new spinochromes, echinamines A (1) and B (2), were isolated from the sea urchin Scaphechinus mirabilis. Compounds 1 and 2 represent the first examples of natural polyhydroxynaphthazarins with a primary amine group. The structures of 1 and 2 were established by analysis of spectroscopic data and synthesis of their dimethyl ethers.

Caffeic acid metabolites from Eritrichium sericeum cell cultures.

Eritrichium sericeum (Boraginaceae) callus and root cultures were established and analyzed for caffeic acid metabolite (CAM) production. Two substances, (-)-rabdosiin and rosmarinic acid, were identified as main CAMs produced by these cultures. The E. sericeum Er-1 root culture accumulated up to 1.5 % and 4.5 % DW of (-)-rabdosiin and rosmarinic acid, respectively. Rabdosiin in the Lithospermum erythrorhizon callus cultures was produced exclusively as the (+)-enantiomer while in both Eritrichium cultures it occurred as the (-)-enantiomer. The E. sericeum Er-1 culture accumulated 3-fold higher levels of CAMs than the L. erythrorhizon culture. A new compound, named eritrichin, was isolated from the cultured E. sericeum cells. The structure of this compound was established as (2R)-3-(3,4-dihydroxyphenyl)-2-[4-(3,4-dihydroxyphenyl)-6,7-dihydroxy-2-naphthoyloxy]propanoic acid on the basis of spectral data.