Thermal stability of anthocyanin extract of Hibiscus sabdariffa L. in the presence of beta-cyclodextrin

The thermal stability of anthocyanin extract isolated from the dry calyces of Hibiscus sabdariffa L. was studied over the temperature range 60-90 degrees C in aqueous solutions in the presence or absence of beta-cyclodextrin (beta-CD). The results indicated that the thermal degradation of anthocyanins followed first-order reaction kinetics. The temperature-dependent degradation was adequately modeled by the Arrhenius equation, and the activation energy for the degradation of H. sabdariffa L. anthocyanins during heating was found to be approximately 54 kJ/mol. In the presence of beta-CD, anthocyanins degraded at a decreased rate, evidently due to their complexation with beta-CD, having the same activation energy. The formation of complexes in solution was confirmed by nuclear magnetic resonance studies of beta-CD solutions in the presence of the extract. Moreover, differential scanning calorimetry revealed that the inclusion complex of H. sabdariffa L. extract with beta-CD in the solid state was more stable against oxidation as compared to the free extract, as the complex remained intact at temperatures 100-250 degrees C where the free extract was oxidized. The results obtained clearly indicated that the presence of beta-CD improved the thermal stability of nutraceutical antioxidants present in H. sabdariffa L. extract, both in solution and in solid state.     

Physiological analysis of growth and nitrogen metabolism of intercropped pasture species subterranean clover (Trifolium subterraneum L.) and cocksfoot (Dactylis glomerata L.) supplemented with different forms of inorganic nitrogen

Growth and physiological parameters of intercropped subterranean clover (Trifolium subterraneum L.) and cocksfoot (Dactylis glomerata L.) were investigated under controlled and field conditions. Nitrogen nutrition was accomplished in symbiotic and heterotrophic forms in both the species studied under controlled concentration of mineral elements in the media and by in oculation with appropriate rhizobial strain. Intercropped variants were also grown in sand culture as follows: subterranean clover – 100%, cocksfoot – 100%, subterranean clover:cocksfoot– 75:25(%), subterranean clover: cocksfoot– 50:50(%), and subterranean clover:cocksfoot– 25:75(%). In hydroponic cultures, subterranean clover to cocksfoot proportion was always 50:50(%). Subterranean clover reacted positively with growth up to 1.25 mM nitrate concentration in the medium with stimulation of number of nodules formed and their nitrogenase activity. When separately grown, both subclover and cocksfoot reacted with higher plant biomass formation under higher nitrate nutrition. When intercropped, the process of growth stimulation in subclover was more prominent than in cocksfoot.     

Marine Biopolymers as Bioactive Functional Ingredients of Electrospun Nanofibrous Scaffolds for Biomedical Applications

Marine biopolymers, abundantly present in seaweeds and marine animals, feature diverse structures and functionalities, and possess a wide range of beneficial biological activities. Characterized by high biocompatibility and biodegradability, as well as unique physicochemical properties, marine biopolymers are attracting a constantly increasing interest for the development of advanced systems for applications in the biomedical field. The development of electrospinning offers an innovative technological platform for the production of nonwoven nanofibrous scaffolds with increased surface area, high encapsulation efficacy, intrinsic interconnectivity, and structural analogy to the natural extracellular matrix. Marine biopolymer-based electrospun nanofibrous scaffolds with multifunctional characteristics and tunable mechanical properties now attract significant attention for biomedical applications, such as tissue engineering, drug delivery, and wound healing. The present review, covering the literature up to the end of 2021, highlights the advancements in the development of marine biopolymer-based electrospun nanofibers for their utilization as cell proliferation scaffolds, bioadhesives, release modifiers, and wound dressings.