Antimicrobials active metabolites

LAB produce several compounds with antimicrobial properties as a result of nutrient competition with other microorganisms growing in the same niche. These antimicrobial active metabolites consist of nonspecific antimicrobial substances such as short-chain fatty acids (formic, acetic, propionic, butyric, and lactic acids), ethanol and hydrogen peroxide, and toxins including bacteri-ocins (nisin, reuterin, reutericyclin, pediocin, lacticin, enterocin, and others). 

Stadler M et at. New metabolites with nematicidal and antimicrobial activities from the ascomycete Lachnum papyraceum (Karst.) Karst. VII. Structure determination of brominated lachnumon and mycorrhizin A derivatives, J Antibiot 48 158-161, 1995. 

Anke H. etal., Secondary metabolites with nematicidal and antimicrobial activity from nematophagous fungi and Ascomycetes, Can J Bot 73 S932—S939, 1995. 

O. 69 LVh/kg renal and biliary clearance of unchanged drug each contribute approximately 5%. About 30% of the dose is excreted in the feces 53% of the oral dose is excreted in the urine, primarily as metabolites. Of the five metabolites that have been identified, 25-0-desacetyl and 31-hydroxy are the most predominant, and show a plasma metabolite parent ADC ratio of 0.1 and 0.07, respectively. The 25-0-desacetyl metabolite has an activity equal to the parent drug and contributes less than or equal to 10% to the total antimicrobial activity. 

Vermisporin (41) is produced by the fungus Ophiobolus vermisporis [76]. Its structure was determined by chemical degradation to the derivative (42) which was studied by X-ray crystallography and provided the absolute configuration [77]. Vermisporin exhibits antimicrobial activity towards Bacteroides spp (0.25-2 lg/ml), Clostridium perfringens (0.25-2 pg/ml) and methicillin-resistant Staphylococcus aureus (0.12-0.5 pg/ml). A metabolite of Ophiobolus rubellus produces the tetramic acid (43) that has been claimed to be an inhibitor of proline hydroxylase (IC5019pM) [78]. 

Four minor metabolites, psammaplins B-D (503-505) and presammaplin A (506) were isolated from Psammaplysilla purpurea, in addition to psammaplin A (500). Psammaplin B (503) is a thiocyanate bromotyrosine derivative, while psammaplin C (502) is a sulfanamide. Psammaplin D (505) displayed antimicrobial activity and mild tyrosine kinase inhibition [429]. The psammaplins Ai (507) and A2 (508) and aplysinellins A (509) and B (510) were isolated from Aplysinella rhax from both Pohnpei and Palau. These compounds inhibit famesyl protein transferase and leucine aminopeptidase [430]. Another sample of A. rhax from the Great Barrier Reef, Australia contained psammaplin A 11 -sulfate (511) and bisaprasin ll -sulfate (512), both of which inhibited [3H]-l,3-dipropyl-8-cyclopentylxanthine binding to rat brain adenosine Ai receptors [431]. 

Plants have evolved different mechanisms to protect themselves against a great variety of invasive pathogens. As a part of the defense, plants produce a number of secondary metabolites with antimicrobial activity. Many of these compounds are produced constitutively, being present in healthy plants as normal metabolic products. VanEtten et al. proposed the term "phytoanticipin" to define these preformed antimicrobial... 

Stadler M, Anke H, Sterner O (1995) Metabolites with Nematicidal and Antimicrobial Activities from the Ascomycete Lachnum papyraceum (Karst.) Karst V. Production, Isolation and Biological Activities of Bromine-Containing Mycorrhizin and Lachnumon Derivatives and Four Additional New Bioactive Metabolites. J Antibiot 48 149... 

The extraordinary biomedical potential of marine natural products is well documented 4 6 recent reviews provide details of their cytotoxic,7-8 antiviral,9 antiparasitic,10 and antimalarial11 activities. In addition, numerous marine metabolites show useful antimicrobial activity. Although some of... 

Secondary metabolites include essential oils, used in the flavour and fragrance industries. Essential oils are found in over 50 plant families and represent terpenoids and other aromatic compounds accumulating typically at relatively low concentrations (usually <1% of fresh weight, but can be up to 20%), but which have useful antimicrobial activity (Biavati el a/., 2003). Production of essential oils by plants is affected by many factors influencing plant growth. 

A long-lasting open question in the study of Actinomycetes is why this group of bacteria produce such highly diverged compounds as secondary metabolites. It is well known that some of the compounds exhibit antimicrobial activities, which leads to a plausible argument that the defensive function of these compounds is essential for the life of this kind of bacteria in the natural environment, although this simple idea does not fully explain the marked diversity of structure and activity of the secondary metabolites. 

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