ECTS - Teses de Doutoramento

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Percorrer ECTS - Teses de Doutoramento por autor "Pereira, Filipe Jorge da Silva"

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    Lamiaceae extracts and compounds for topical application through nano delivery systems
    (2017) Pereira, Filipe Jorge da Silva; Escola de Ciências e Tecnologias Saúde
    Antibiotic resistance is one of the major health problem affecting every continent, whether developed or developing countries. This problem is responsible of a high number of patients and a leading cause of deaths worldwide, without an effective form of therapy. The developments in the nanotechnology field has led to more efficient delivery systems, while new structures unveiled through natural resources showed high biological activity never studied before. The combination of a new drug delivery strategy with new bioactive molecules can lead to new therapeutic forms against this type of infections. With this work, it is analysed the potencial and ability of 7?-acetoxy-6?- hydroxyroyleanone as a novel compound for the treatment of infections associated with resistant bacterias. In the same way, it is proposing that the combination of a therapeutic form of natural source (extract ou isolated compound) with an new technique of delivery using different types of nanoparticles for the treatment of topical infections. 7?-acetoxy-6?-hydroxyroyleanone extract from Plectranthus grandidentatus was optimized, through seven different methods of extraction. The highest quantity of the 7?- acetoxy-6?-hydroxyroyleanone was obtained through supercritical fluid extraction, delivering an amount of AHR about six times higher than that of the second-best method tested. 7?- acetoxy-6?-hydroxyroyleanone isolated was used for the characterization studies of their physicochemical properties. Important data, such as, molecular and crystal structure of 7?- acetoxy-6?-hydroxyroyleanone was obtained from single crystal X-ray diffraction and the thermal behavior of the compound was studied by differential scanning calorimetry. The mechanism of action of high antibacterial activity and low cytotoxicity of 7?-acetoxy-6?-hydroxyroyleanone was studied on a type of Methicillin-resistant Staphylococcus aureus strain. In this approach, different studies were carried out. 7?-acetoxy-6?- hydroxyroyleanone had a non-significant effect in passive permeability, at same time, bacteria treated with this royleanone displayed cell wall disruption, without cell lysis. The combination of nanoparticles with natural products was preliminary tested using two plants from Lamiaceae family. Different extracts from Lavandula stoechas ssp. luisieri and Lavandula pedunculata were prepared and established their antioxidant profile by lipid peroxidation inhibition and the antioxidant activity confirmed. Due to their high antioxidant activity, phenolic content and flavonoid amount, methanol extracts of Lavandula stoechas ssp.luisieri and Lavandula pedunculata were selected and encapsulated into Poly(lactic-co-glycolic acid) nanoparticles. The encapsulation of the extracts resulted in well-defined spherical shape PLGA nanoparticles and with a high encapsulation efficiency (?96%). Preliminar epidermal permeation of both extracts through ex-vivo human epidermis and their in vitro cytotoxicity in human keratinocytes studies were suggestive of their low risk of toxicity. The combination of nanoparticles with 7?-acetoxy-6?-hydroxyroyleanone was also studied in this thesis. Through a different approach, distinct silver nanoparticles were successful synthesized using citrate and borohydride salts as reducing agents. Ampicillin, as model drug, and 7?-acetoxy-6?-hidroxyroyleanone as new therapeutic compound were associated with both type of silver nanoparticles. Particle characterization showed small, spherical and monodisperse nanoparticles. The antibacterial capacity of each compound was higher after conjugation with silver nanoparticles. In vivo skin irritation test conducted in animal models showed absence of erythema or any skin color changes. The study developed on this new molecule has resulted in promising results for future application as topical formulation. The knowledge of its chemical and mechanistic properties may result in structures with better therapeutic activity and minor adverse side effects. Ultimately, their combination with nanotechnology may lead to advantageous pharmacological properties for people infected with this type of bacteria.