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In the recent past, the human gut microbiota has gained increasing interest as a target for the delivery of substances due to the observed interaction between the microbiome, nutrition and health. The water-soluble vitamin niacin showed first effects on the composition of the gut microbiota. In order to enhance the availability of niacin in the ileocolonic region, where most of the microorganism are located, an early systemic absorption of niacin in the stomach and small intestine must be prevented. Therefore, two active forms of niacin (nicotinic acid (NA) and nicotinamide (NAM)) were encapsulated by a protective shellac coating applied via fluidized bed coating. The modulation of the release profile of niacin was assisted by a newly designed in vitro dissolution test and verified by a human bioavailability study with 10 healthy volunteers for each group. Different intrinsic effects on the release profile such as derived from the properties of the encapsulated compound were investigated. The active substance core was produced by a one-step spray granulation and a two-step process (extrusion with subsequent spheronisation). The latter method achieved a higher particle yield and required a lower use of shellac in relation to the mass of active substance. As an alternative to shellac coated microcapsules, the incorporation of niacin into pectin-zein hydrogel beads was characterized. A precise targeted release of niacin into the ileocolonic region in vitro and in vivo was reached by using a shellac based coating with adapted intermediate subcoatings consisting of either citric acid for NAM or sodium bicarbonate of NA. The subcoatings were able to control the effect of the physico-chemical properties of the encapsulated compound and to influence the pH-dependent dissolution of the surrounding shellac coatings. The designed in vitro dissolution test for the targeting provided a precise instrument to predict the release behavior in humans.

In recent years utilizing biopolymer interactions, or crosslinking-assembled spherical structures, enabled the encapsulation and targeted delivery of numerous active ingredients. The self-assembly of proteins such as zein or casein micelles has already been explored as a vehicle for delivery of hydrophobic bioactive compounds, while the use of alginate-protein or chitosan-protein complexes has been introduced very recently, mostly for encapsulation of pharmaceutical model drugs. In this study we focus on using alginate, chitosan and proteins as biopolymer building blocks for encapsulation of quercetin, a representative poorly water-soluble lipophilic polyphenolic antioxidant. The approach of improving quercetin solubility in a mixture of ascorbic acid was evaluated, and compared to plain compounds based on their antioxidant capacity. Electrostatic complexation between alginate and chitosan and reinforcement with whey proteins was conducted and mediated additionally by temperature (70°C) and ionic cross-linking. The encapsulation of both quercetin and ascorbic acid was achieved, enabling to entrap up to 66% of quercetin and 54% of ascorbic acid. Macro-sized spherical particles of alginate-chitosan and whey proteins-chitosan were produced ranging up to 2 mm in size, with the use of chitosan enabling the production of smaller particles. Whey protein-chitosan particles were less spherical, but provided the most retarded, prolonged release of quercetin from the particles in simulated gastric and intestinal fluids.

Bioactive features of diverse nutraceutical compounds as novel therapeutic supplements led to an increased interest of pharmaceutical and food domains in obtaining encapsulated dosage forms of those compounds that enable their wide applications. Polyphenolic antioxidants impart the largest number of evaluated and established antioxidant properties, however the possibility of synergistic effect of polyphenols with other bioactive compounds, such as amino acids and vitamins has not been evaluated properly. The present study was focused on defining the antioxidant potential of quercetin as a model polyphenolic compound in combination with ascorbic acid and amino acids L-lysine and taurine, aiming to obtain the most potent nutraceutical mixture that was encapsulated in alginate-based hydrogel particles by ionotropic gelation. The assessment of synergistic antioxidant properties by the ABTS, DPPH and FRAP assays revealed that although L-lysine and taurine water solutions did not exert antioxidant capacity, they enhanced the antioxidant potential of their binary mixtures with quercetin, providing up to 30% higher antioxidant capacity than just plain quercetin solutions. The combination of quercetin, L-lysine and ascorbic acid (each 150 mg/L), exhibited the most potent antioxidant properties, with up to 2-fold higher antioxidant capacity than just plain quercetin (150 mg/L) or 3-fold higher than plain ascorbic acid (150 mg/L). By encapsulating the stated synergistic mixture in 2% sodium alginate via calcium-induced crosslinking, 78% of rosmarinic acid was entrapped inside the freeze dried particles, along with 62% of vitamin C and 86% of L-lysine (established by spectrophotometric assays). Although L-lysine contributed less by its antioxidant properties, its cationic nature may have contributed to the augmented encapsulation efficiency of the active compounds by enhanced crosslinking due to the polyelectrolyte character of alginate-L-lysine matrix. The obtained results provide a novel approach to establishing innovative formulations of potent, functional nutraceutical dosage forms.

In recent years utilizing biopolymer interactions, or crosslinking-assembled spherical structures, enabled the encapsulation and targeted delivery of numerous active ingredients. The self-assembly of proteins such as zein or casein micelles has already been explored as a vehicle for delivery of hydrophobic bioactive compounds, while the use of alginate-protein or chitosan-protein complexes has been introduced very recently, mostly for encapsulation of pharmaceutical model drugs. In this study we focus on using alginate, chitosan and proteins as biopolymer building blocks for encapsulation of quercetin, a representative poorly water-soluble lipophilic polyphenolic antioxidant. The approach of improving quercetin solubility in a mixture of ascorbic acid was evaluated, and compared to plain compounds based on their antioxidant capacity. Electrostatic complexation between alginate and chitosan and reinforcement with whey proteins was conducted and mediated additionally by temperature (T=70°C) and ionic cross-linking (Ca2+). The encapsulation of both quercetin and ascorbic acid was achieved, enabling to entrap up to 71% of quercetin and 55% of ascorbic acid. Micro-sized spherical particles of alginate-chitosan and whey proteins-chitosan were produced ranging up to 940 µm, with alginate-chitosan particles producing smaller particles. Whey protein-chitosan particles were less spherical, but provided much slower release of quercetin from the particles in simulated gastric and intestinal fluids.