Brazilian stingless bee propolis and geopropolis: promising sources of biologically active compounds

ABSTRACT Stingless bee products such as honey, pollen, propolis, and geopropolis have been used for centuries in traditional medicine for the treatment of several illnesses. Investigation of the biological activity of stingless bee products, especially propolis and geopropolis, has revealed promising therapeutic properties. About 20% of total Neotropical stingless bees can be found in Brazil. Despite the species diversity, studies on their biological activity are scarce. The present review focuses on the antioxidant and antimicrobial activities of propolis and geopropolis from Brazilian stingless bees. In addition, the toxicity of these natural products was addressed. In order to provide new evidences for the toxic potential of propolis and geopropolis components, an in silico analysis was performed using the ADMET PredictorTM software. We observed that most of studies evaluated only crude ethanol extracts of a limited number of stingless bees species. Propolis and geopropolis displayed antioxidant capacity and antimicrobial activity. Concerning the toxic potential, the extracts of stingless bees propolis and geopropolis were considered safe. Nonetheless, in vitro and in vivo toxicological studies are still necessary.

Site-specific adhesion of Staphylococcus epidermidis (RP12) in Ti-Al-V metal systems.

Staphylococcus epidermidis (RP12) adhesion patterns were studied on the following titanium (Ti)-aluminium (Al)-vanadium (V) metal systems: (i) microfabricated samples consisting of Ti, Al and V islands deposited onto Ti or V substrata, (ii) pure Ti, Al and V metals, and (iii) medical grade Ti6Al4-V alloy. All of these surfaces were covered with their respective oxides formed upon exposure of the metals to air. Quantitative analysis of the number of cells bound per unit area indicates that S. epidermidis (RP12) exhibits greatest adhesion to pure V surfaces. When exposed to surfaces having controlled spatial variations in chemical composition on the 10 microns scale (microfabricated samples), the bacteria preferentially populate V islands versus Ti or Al substrata. In the case of the biphasic Ti6Al4V alloy, the bacteria tend to adhere to V-rich, mixed phase regions and phase boundaries. These findings demonstrate that enhanced and preferential adhesion of S. epidermidis (RP12) occurs on V surfaces in Ti-Al-V metal systems and suggest that bacterial interactions are influenced by surface oxide composition.

Cell biology and molecular mechanisms in artificial device infections.

Biomaterials are being used with increasing frequency for tissue substitution. Complex devices such as total joint replacement and the total artificial heart represent combinations of polymers and metal alloys for system and organ replacement. The major barrier to the extended use of these devices is bacterial adhesion to biomaterials, which causes biomaterial-centered infection, and the lack of successful tissue integration or compatibility with biomaterial surfaces. Adhesion-mediated infections are extremely resistant to antibiotics and host defenses and frequently persist until the biomaterial or foreign body is removed. The pathogenesis of adhesive infections is related, in part, to preferential colonization of "inert" substrate whose surfaces are not integrated with healthy tissues composed of living cells and intact extracellular polymers. Tissue integration is an interesting parallel to microbial adhesion and is a desired phenomenon for the biocompatibility of certain implants and biomaterials. Tissue integration requires a form of eukaryocytic adhesion or compatibility with possible chemical integration to an implant surface. Many of the fundamental principles of interfacial science apply to both microbial adhesion and to tissue integration and are general to and independent of the substratum materials involved. Interactions of biomaterials with bacteria and tissue cells are directed not only by specific receptors and outer membrane molecules on the cell surface, but also by the atomic geometry and electronic state of the biomaterial surface. An understanding of these mechanisms is important to all fields of medicine and is derived from and relevant to studies in microbiology, biochemistry, and physics.(ABSTRACT TRUNCATED AT 250 WORDS)

Microcrystals of the annexin, p68: paracrystal to crystal transition and molecular packing as determined by electron microscopy and image reconstruction.

The calcium-sensitive, membrane-binding annexin, p68, has been crystallized from solutions of polyethylene glycol and ammonium sulfate. Our electron microscopy and X-ray diffraction data indicate that p68 crystals are tetragonal, in space group P4(1), and have unit cell dimensions of a = b = 68.4 A and c = 209.6 A. The mechanism of crystallization from polyethylene glycol involves a transition from a paracrystalline form to ordered crystals by lateral reordering of chains of molecules extended along the c axis. These chains are directional and might reflect a mechanism whereby the two different ends of (chains of) the p68 molecules interact with different membranes.