Biological Sciences
Polyene
Polyenes are a group of organic compounds characterized by alternating single and multiple carbon-carbon bonds. In biological sciences, polyenes are known for their antifungal properties and are commonly used in the treatment of fungal infections. They work by disrupting the cell membranes of fungi, leading to their destruction. Polyenes are important in the development of antifungal medications.
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3 Key excerpts on "Polyene"
eBook - PDFMedicinal Natural Products
A Biosynthetic Approach
- Paul M. Dewick(Author)
- 2009(Publication Date)
- Wiley(Publisher)
Box 3.8 Polyene Antifungals The Polyene antifungals are a group of macrocyclic lactones with very large 26–38-membered rings. They are characterized by the presence of a series of conjugated E double bonds and are classified according to the longest conjugated chain present. Medicinally important ones include the heptaene amphotericin B and the tetraene nystatin. There are relatively few methyl branches in the macrocyclic chain. The Polyenes have no antibacterial activity but are useful antifungal agents. Their activity is a result of binding to sterols in the eukaryotic cell membrane; this action explains the lack of antibacterial activity, because bacterial cells do not contain sterol components (see page 241). Fungal cells are also attacked rather than mammalian cells, since the antibiotics bind about 10-fold more strongly to ergosterol, the major fungal sterol (see page 252), than to cholesterol, the main animal sterol component (see page 251). This binding modifies the cell wall permeability and leads to formation of transmembrane pores that allow K + ions, sugars, and proteins to be lost from the microorganism. Though binding to cholesterol is less than to ergosterol, it is responsible for the observed toxic side-effects of these agents on humans. The Polyenes are relatively unstable, undergoing light-catalysed decomposition, and are effectively insoluble in water. This insolubility actually protects the antibiotic from gastric decomposition, allowing oral treatment of infections in the intestinal tract. Amphotericin is an antifungal Polyene produced by cultures of Streptomyces nodosus and contains principally the heptaene amphotericin B (Figure 3.46) together with structurally related compounds, e.g. the tetraene amphotericin A (about 10%) which is the 28,29-dihydro analogue of amphotericin B. Amphotericin A is much less active than amphotericin B.
eBook - PDF- Gupta, V K(Authors)
- 2018(Publication Date)
- Daya Publishing House(Publisher)
Some compounds contain aliphatic side chain with an additional aromatic moiety (Tereshin, 1976).Other highly characteristic feature of Polyene antibiotics is large number of hydroxyl groups present on the molecule varying from 6 to 14. Polyenes are extremely unstable in the presence of oxidants and UV rays, extreme pH, stable between 5-6 pH and thermo labile (prolonged heating above 50ºC). Polyene contains carbon, hydrogen, oxygen and in some instances nitrogen. The amino group present in some of the Polyene is associated with an amino sugar moiety that is connected to the macrolide ring through glycoside bond. Polyenes are classified on the basis of number of conjugated double bonds (Berdy, 1980). They are: triene, tetraene, pentaene, hexaene, heptaene, octaene, oxoPolyene and mixed Polyene groups. Different sophisticated spectroscopy techniques, like field desorption, fast atom bombardment (Rinehart, 1982) and secondary ion mass spectroscopy (Harada et al ., 1982), high resolution 1 H NMR and, X-ray structure analysis (Mechlinski et al ., 1970) and two dimensional 13 C NMR actonide analysis (Rychnovsky et al ., 1997) were employed in Polyene macrolide antibiotics structure elucidation. Trienes The trienes Polyene antibiotics showed some atypical properties. Aurantinin and proticin produced by Bacillus sp., showed antibacterial activity against Gram (+ve and –ve) bacteria (Omura et al ., 1976; Nishikiori This ebook is exclusively for this university only. Cannot be resold/distributed. et al ., 1978). Resistaphylin produced by Streptomyces showed strong Gram +ve activity (Aizawa et al ., 1971). The triene showed antitumor activity (Aszalos et al ., 1968). Rapamycin and demethoxy rapamycin are structurally proved atypical trienes (Findlay, 1982) and chromatrienin produced by Actinimyces, chromogenes var trienicus showed promising antifungal activity (Vezina et al ., 1975).
- Monika Waksmundzka-Hajnos, Joseph Sherma(Authors)
- 2010(Publication Date)
- CRC Press(Publisher)
887 33 HPLC Analysis of Polyacetylenes Lars P. Christensen and Kathrine B. Christensen 33.1 INTRODUCTION Polyacetylenes belong to a class of molecules containing two or more triple bonds and constitute a distinct group of relatively unstable, reactive, and bioactive natural products. Polyacetylenes are widespread in nature, occurring in plants, fungi, lichens, moss, microorganisms, algae, and marine invertebrates [1–9]. The triple bond functionality of polyacetylenes makes these natural products a very interesting group of compounds whose reactivity toward proteins and other biomolecules may explain their wide variety of bioactivities. Among the most interesting bioactivities of polyacetylenes are their antitumor and anti-inflam-matory activity as well as their activity against fungi and gram-positive and gram-negative bacteria [8–12]. In particular, aliphatic C 17 -polyacetylenes of the falcarinol type, which are widespread in common food and medicinal plants of the Apiaceae and Araliaceae plant families, are of interest. This type of polyacetylenes is highly cytotoxic and has a potential anticancer effect. In addition, they possess anti-inflammatory, anti-platelet-aggregatory, antibacterial, antimycobacterial, antifungal, neuritogenic, and immune-stimulatory effects, which may explain the beneficial effects associated with food and medicinal plants containing these compounds [9,10,12]. Fungi and microorganisms also provide a source for special polyacetylenes with interesting bioactivities that can be used to develop new antibiotics and anticancer agents [8,13]. Polyacetylenes are often unstable, being sensitive to ultraviolet (UV) light as well as to oxidative, thermal, and pH-dependent decomposition, which often leads to substantial chal-lenges in their isolation, quantification, and characterization [1,9,12,14].
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