Abstract
The (trans)esterification reaction of bacterial biopolymers with a selected bioactive compound with a hydroxyl group was applied as a convenient method for obtaining conjugates of such compound. Tyrosol, a naturally occurring phenolic compound, was selected as a model of a bioactive compound with a hydroxyl group. Selected biodegradable polyester and polyamide, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) and poly-γ-glutamic acid (γ-PGA), respectively, were used. The (trans)esterification reactions were carried out in melt mediated by 4-toluenesulfonic acid monohydrate. The structures of (trans)esterification products were established at the molecular level with the aid of ESI-MS2 (electrospray ionization tandem mass spectrometry) and/or 1H NMR (nuclear magnetic resonance) techniques. Performed analyses confirmed that the developed method leads to the formation of conjugates in which bioactive compounds are covalently bonded to biopolymer chains. The amount of covalently bonded bioactive compounds in the resulting conjugates depends on the type of biopolymers applied in synthesis.
Highlights
Design of biodegradable delivery systems for bioactive substances is a rapidly developing field.The aim of designing delivery systems is modification of properties of bioactive molecules, such as solubility, stability and bioactivity, and improve the delivery efficiency
It was found that the “one-pot” transesterification method developed by us for obtaining conjugates of bioactive compounds with the carboxyl group [17] could be an implement for preparing conjugates of bioactive compounds with a hydroxyl group
The method for the preparation of conjugates consisting of bioactive compounds with hydroxyl group and oligomers from bacterial biopolymers has been discussed in detail
Summary
Design of biodegradable delivery systems for bioactive substances is a rapidly developing field. The aim of designing delivery systems is modification of properties of bioactive molecules, such as solubility, stability and bioactivity, and improve the delivery efficiency. For these purposes biodegradable, biocompatible and nontoxic polymeric carriers might be applied [1,2,3,4]. Potential uses of polyhydroxyalkanoates (PHAs) in polymeric delivery systems of bioactive compounds have been evaluated in a number of studies—for example, delivery systems for steroids [5], antibiotics [6,7], or antitumor agents [8,9]. The PHAs are accumulated as granules in the cell, reaching 90% levels of dry cell mass [10]
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