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- Evaluation of Humulus lupulus L. Therapeutic Properties for the Treatment of Skin DiseasesPublication . Guiomar, Liliana Sofia Lima; Oliveira, Ana Cristina Palmeira de; Oliveira, José António Martinez Souto de; Vaz, Cátia Alexandra VicenteThe skin is the largest organ of the human body and is responsible for numerous vital functions as being a physical protective barrier against the invasion of pathogenic microorganisms, penetration of harmful chemicals, and of ultraviolet rays, while having also important roles as in body fluid homeostasis and the elaboration of immune and sensitive responses. The cooperation between the various constituting elements of the skin (keratinocytes, fibroblasts, immune system cells, motor and sensitive nerve fibres, glands, blood and lymphatic vessels) together with the microorganisms residing on its surface is important to keep the body healthy. Numerous common skin disorders such as atopic dermatitis, psoriasis and acne can be associated with an individual's genetic predisposition, but also with an imbalance in the microflora of the skin or even to an uncontrolled activation of responses of the innate and adaptive immune system due often to over-expression of proteins such as cyclooxygenase-2 (COX-2), responsible for the genesis of chronic inflammatory processes and oxidative stress that lead to the production of molecules such as nitric oxide (NO) and reactive oxygen species (ROS) that, when in excess, become toxic and harmful to the cells. Humulus lupulus Linnaeus, belonging to the Cannabaceae family, is popularly used in beer making and in traditional medicine for its relaxing therapeutic properties, such as the treatment of insomnia and anxiety. The inflorescence of H.lupulus is the part of the plant mostly used because it is where the lupulin gland is located, an organ harbouring mainly 15-30% of resins (hard and soft resins), essential oils, polyphenols, among other minority compounds responsible for the medicinal character of the plant. These secondary metabolites of H.lupulus are known to have a high anti-inflammatory, anxiolytic, antidepressant, antioxidant and antimicrobial potential. In this dissertation, the capacity of aqueous extracts of the flower, the mix aqueous extract (mixture of stems, leaves and flowers), the flower hydrolate and the mix hydrolate of H.lupulus was studied to decrease multiplication of Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis and Cutibacterium acnes) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria by the microdilution method and in the alteration of the metabolic activity of 3T3 fibroblast cells and RAW macrophages from mouse skin by the colorimetric method, 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT). The impact of these extracts on the production of NO was also evaluated by the Griess method, production of ROS by fluorescent molecules such as H2DCFDA, and on the expression of COX-2 an agent involved in the inflammation processes after activation of macrophages by lipopolysaccharide (LPS) by Western blot. The results show that H.lupulus flower hydrolate presents higher antibacterial capacity (especially against Gram-positive bacteria), strong antioxidant capacity, because it significantly reduces the production of ROS reduces inflammation, decreasing the production of NO and decreasing the expression of COX-2 by LPS activated macrophages. The remaining extracts also presented anti-inflammatory and antioxidant effects, but less evident than the flower hydrolate. Mix hydrolate and aqueous extract showed a low antibacterial effect for some of the strains under study and did not significantly alter the metabolic activity of 3T3 fibroblasts and RAW macrophages. This study demonstrated that H.lupulus, mainly the inflorescence of the plant (flowers), has chemical elements with anti-inflammatory, antioxidant and antibacterial capacities supporting the concept of being H.lupulus products very interesting to be used in treatment and prevention of diseases of the skin while respecting its physiological constitution . However, further studies are necessary in order to better understand the profile of the different chemical compounds of H.lupulus and to establish the best effective concentration yet non-toxic for the cells and microbiota of skin.