Polyphenols, plant secondary metabolites, are present in human diet and have been widely used for medical and cosmetic purposes. They possess beneficial features such as antioxidant, immunomodulatory, anti-cancer and antibacterial activity. There is some evidence that these phytochemicals can improve wound healing. However, more and more data suggest that, under certain conditions, they can act in a different, often unpredictable way. Some investigations indicate that polyphenols, generally known as antioxidants, can exhibit pro-oxidant, and therefore cytotoxic, activity. Hence, the ability of phytochemicals to induce apoptosis of cancer cells and bacterial cell damage may be, at least partly, due to their prooxidant properties. Phytocompounds enter the body through the digestive system where they undergo metabolic processes that often change their chemical features. The gastrointestinal microbiome interacts with phytochemicals and influences their bioavailability and absorption in the gut. Except for biochemical changes of plant polyphenols in the host, the achievement of therapeutic concentration in vivo may be the main problem in the determination of their real efficacy. Ambiguous results of some studies demonstrate the need for the development of more accurate and standardized methods for the evaluation of polyphenols' properties. Better understanding of human body-polyphenol interactions is crucial for more effective use of these phytochemicals in disease prevention and therapy.

The antifungal activity of the saponin-rich fractions (SFs) from Medicago sativa (aerial parts and roots) and Saponaria officinalis (used as a well-known source of plant saponins) against Candida albicans reference and clinical strains, their yeast-to-hyphal conversion, adhesion, and biofilm formation was investigated. Direct fungicidal/fungistatic properties of the tested phytochemicals used alone, as well as their synergy with azoles (probably resulting from yeast cell wall instability) were demonstrated. Here, to the best of our knowledge, we report for the first time the ability of saponin-rich extracts of M. sativa and S. officinalis to inhibit C. albicans germ tube formation, limit hyphal growth, reduce yeast adherence and biofilm formation, and eradicate mature (24 h) Candida biofilm. Moreover, M. sativa SFs (mainly obtained from aerial parts), in the range of concentrations which were active modulators of Candida virulence factors, exhibited low cytotoxicity against the mouse fibroblast line L929. These properties seem to be very promising in the context of using plant-derived SFs as potential novel antifungal therapeutics supporting classic drugs or as ingredients of disinfectants. INTRODUCTIONCandida albicans is probably the best known and at the same time the most effective opportunistic fungal pathogen of humans and animals. It constitutes a commensal microflora in the gastrointestinal and genitourinary tracts of .70 % of humans. However, in certain circumstances C. albicans could be pathogenic to critically ill, immunocompromised patients or even to healthy persons. It causes a diverse range of pathologies -from local cutaneous and mucosal infections (e.g. candidiasis of nail shafts and nails, oropharyngeal candidiasis, intestinal candidiasis) to lifethreatening systemic infections, such as candidaemia, fungal pneumonia, meningitidis or endocarditis (Cannon et al., 2009;Kabir et al., 2012;Kabir & Ahmad, 2013;Sardi et al., 2013; Tlamçani & Er-rami, 2013). Endogenous candidaemia and the carrier state are the main mechanisms of Candida spp. spread and transmission, although exogenous infections are also possible (Mathé & van Dijck, 2013;Sardi et al., 2013). The pathogenicity and high invasiveness of C. albicans arise from the broad range of its virulence factors. These include tissue-damaging hydrolytic enzymes: proteases (mainly secreted aspartic proteinases), phospholipases and haemolysins, but first of all the agents/abilities contributing to its strong adherence (e.g. two main C. albicans adhesions: agglutinin-like sequence and hyphal wall protein-1), biofilm formation and the transformation of morphological forms (yeast-to-hyphal). Also, the ability of C. albicans to survive in various anatomical body sites and to evade host defences seems to be essential (Chai et al., 2009;Chandra et al., 2001;Gropp et al., 2009;Sardi et al., 2013).Invasive candidiasis usually results from tissue colonization by yeast and formation of biofilm -the structured multicellular microbial communities embedded in a self-...

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In summary, platelets even after the medical expiry date are still a good source of antimicrobial low molecular weight proteins (PMPs). Testing of bacterial resistance to PMPs may be advisable as a predictive indicator of susceptibility to treatment of infections such as infective endocarditis and other local infections of biofilm nature.

Biofilms are probably one of the most common structures formed by microorganisms in various environments. The higher resistance of such microbial communities to stress conditions, including antibiotics and host immune response, is recently extensively studied. However, the weak activity of phagocytic cells against microbial biofilm is not yet fully understood and explained. The aim of this study was: (1) a qualitative and quantitative comparison of cell components/products released from Staphylococcus aureus biofilm or planktonic cultures, (2) evaluation of the influence of such cell components/products on murine leukocytes secretory function. For this, mouse peritoneal leukocytes were stimulated with biofilm or planktonic staphylococcal cultures or their acellular filtrates, and then the production of cytokines (TNF-α, IL-6, IL-10, MCP-1 and MIP-1α), hemolytic activity and staphylokinase (SAK) production was determined. It was found that similar staphylococcal components/products possessing the immunomodulatory properties, were present in both, biofilm and planktonic filtrates. Moreover, these compounds were similarly active in the stimulation of TNF-α and MCP-1 release from leukocytes. The hemolytic activity and SAK release by planktonic and biofilm cultures were also comparable. What is interesting, stronger stimulatory activity of biofilm-derived components/products of clinical S. aureus strains in the case of MIP-1α, IL-6 and IL-10 was noticed. On the other hand, taking into consideration the reference strains, MIP-1α production was enhanced by “planktonic filtrates”. Thus, in our study it was proved, first of all, that biofilm is not a structure fully separated from the external environment. Second, the influence of these S. aureus constituents/metabolites on leukocytes seems to be more strain-dependent than culture phenotype-dependent. The lack of one common profile of biofilm and planktonic S. aureus cultures/filtrates biological activity indicates that the disturbances in cytokines’ production could not be the only reason for the so-called “frustrated phagocytosis”, connected with enhanced biofilm resistance.