Water-insoluble antimicrobial active

The acid-instabihty of erythromycin makes it susceptible to degradation in the stomach to intramolecular cyclization products lacking antimicrobial activity. Relatively water-insoluble, acid-stable salts, esters, and/or formulations have therefore been employed to protect erythromycin during passage through the stomach, to increase oral bioavakabihty, and to decrease the variabiUty of oral absorption. These various derivatives and formulations also mask the very bitter taste of macroHdes. 

The water-soluble and water-insoluble parts of the methanol extract of Achillea sintenisii Hub. Mor. were assayed for their antimicrobial activities against 12 bacteria and 2 yeasts [26]. No activity was exhibited by the water-soluble subfraction, whereas the water-insoluble subtraction of the methanol extract was found to be active against some of the test microorganisms studied. 

Volatile or essential oils, as their name implies, are volatile in steam and are generally complex mixtures of hydrocarbons and oxygenated compounds derived from these hydrocarbons. The odour and taste of volatile oils is mainly determined by these oxygenated constituents. In chemical structure, most essential oils are terpenoids in origin. Testing and evaluation of the antimicrobial activity of essential oils is difficult because of their volatility, their water insolubility and their complexity. However, in recent years a large number of studies have been conducted on the antimicrobial activity of essential oils from the Anthemideae tribe. These reports concerned mainly the genera Achillea and Artemisia. 

The most common biopolymers derived from animals are chitin and chito-san. Chitin is a macromolecule found in the shells of crabs, lobsters, shrimps, and insects. The primary unit in the chitin polymer is 2-deoxy-2-(acetylamino) glucose. Chitin can be degraded by chitinase. Chitosan is a modified natural carbohydrate polymer derived from deactylation of chitin, which occurs principally in animals of the phylum Arthropoda. Chitosan is also prepared from squid pens. Chitin is insoluble in its native form but chitosan, the partly deacetylated form, is water soluble. The materials are biocompatible and have antimicrobial activities as well as the ability to absorb heavy metal ions [16]. 

Numerous researchers found lower antimicrobial activity of aqueous extracts in comparison with acetone, methanol, or other organic solvent extracts (Land and Lundstrom 1998 Madamombe and Afolajan 2003 Rankovic et al. 2008 Kosanic et al. 2010). The reason for the weak activity of aqueous extracts is that active substances present in the thaUi of Uchens are insoluble or poorly soluble in water (Kinoshita et al. 1994). 

The use of silver nitrate and colloidal silver in wounds dates from the mid-nineteenth century and the term oligodynamic was applied to the antimicrobial action of heavy metals diluted in water [9]. Over the years, attempts to put silver in contact with wounds produced a number of electrolytic methods [9] as well as use of solutions of silver nitrate, in this case as late as 1965 [16]. However, the imbalance of sodium, potassium and chloride caused by silver nitrate in these cases was unsatisfactory due to the number of resulting side effects. These include in some cases methemoglobinemia from reduction of nitrate to nitrite. In 1968, a complex (AgSD) formed from a sulfonamide and silver was introduced in attempts to combine the oligodynamic action of the heavy metal with the antibacterial effect of the sulfonamide [17]. The insoluble product, which is used as a 1% cream, has suitable properties and excellent wide spectrum antibacterial activity, and is used worldwide for burn prophylaxis and other infectious skin conditions [9]. Side effects are few, the major one being leukopenia. The properties and mode of action of AgSD have been reviewed [9,18]. 

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