Abstract

Owing to its antibacterial, anti-inflammatory, and antioxidant activities, in the last few years, lavender essential oil (LVO) has been used in medical applications as a promising approach for treating infected wounds. However, the practical applicability of LVO is limited by its high volatility and storage stability. This study aimed to develop a novel hybrid hydrogel by combining phytic acid (PA)-crosslinked sodium alginate (SA) and poly(itaconic anhydride-co-3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5] undecane (PITAU) and evaluate its potential effectiveness as an antibacterial wound dressing after incorporating LVO. The influence of the mass ratio between SA and PITAU on the properties and stability of hydrogels was investigated. After LVO loading, the effect of oil addition to hydrogels on their functional properties and associated structural changes was studied. FTIR analysis revealed that hydrogen bonding is the primary interaction mechanism between components in the hybrid hydrogels. The morphology was analyzed using SEM, evidencing a porosity dependent on the ratio between SA and PITAU, while LVO droplets were well dispersed in the polymer blend. The release of LVO from the hydrogels was determined using UV-VIS spectroscopy, indicating a sustained release over time, independent of the LVO concentration. In addition, the hybrid hydrogels were tested for their antioxidant properties and antimicrobial activity against Gram-positive and Gram-negative bacteria. Very good antimicrobial activity was obtained in the case of sample SA_PITAU3+LVO10% against S. aureus and C. albicans. Moreover, in vivo tests showed an increased antioxidant effect of the SA_PITAU3+LVO10% hydrogel compared to the oil-free scaffold that may aid in accelerating the healing process of wounds.

Abstract

In many European countries Arnica montana is decreasing due to intensification or abandonment of traditional extensive land use and thus is considered endangered. In Romania the species is also decreasing due to excessive collecting for pharmaceutical and cosmetic purposes, but it is still relatively common in montane nutrient-poor grasslands and successional vegetation of forest clearings on acidic soil. In this study we analysed habitats and population structure of A. montana in the Romanian NE Carpathians. We asked for differences in population structure between habitat types and how population structure is related to environmental conditions. We investigated population structure and habitat characteristics in 25 populations of A. montana on three 1 m x 1 m-plots each (total of 75 plots). The plot-based assessment of the population structure included the numbers of rosettes (rosette density), flower heads (flower head density), flowering rosettes and flower stems per flowering rosette. From these variables we calculated the proportions of flowering and vegetative rosettes and the number of flower heads per flowering rosette. Habitats were characterised using climatic data (including elevation), land use types (grazing, mowing or abandonment), vegetation types, soil measurements (pH, several nutrient elements, organic matter content) and N supply on basis of plant indicator values. Vegetation types were defined by using hierarchical clustering and linked to phytosociological syntaxa based on diagnostic species. Observed habitat types included Mountain hay meadows, Species-rich Nardus grasslands and Alpine and subalpine heathlands according to the European Habitats Directive. DCA analysis was used for detecting floristic gradients, which were subsequently correlated to environmental conditions. Relationships between rosette density, proportion of vegetative rosettes, flower head density and number of flower heads per flowering rosette and environmental variables were assessed using GLMs. Five syntaxa with A. montana were identified: Festuco rubrae-Agrostietum capillaris nardetosum strictae, Scorzonero roseae-Festucetum nigricantis, Violo declinatae-Nardetum strictae, Cetrario-Vaccinietum gaultherioidis and Campanulo abietinae-Vaccinietum myrtilli. While vegetation composition was mainly correlated with altitude and soil variables such as pH and organic matter content, altitude was an important predictor for the proportion of flowering rosettes of A. montana, which decreased with altitude. Rosette density of A. montana varied between habitat types and was highest in Mountain hay meadows and lowest in plant communities dominated by tall plants with high cover. Organic matter content of the soil was the only important (negative) predictor for the number of flower heads per rosette, while a hump-shaped correlation was found between the density of inflorescences and the soil pH, with a maximum around pH 4.5. Grassland management was also an important factor for rosette density of A. montana, suggesting that maintaining and promoting traditional land use practices will be the most effective measure for the species' conservation.

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