Stability of pectin-based drug delivery systems

Pectins are natural polysaccharides, which show great potential in drug delivery systems. Pectins are made of several structural elements the most important of which are the homogalacturonan (HG) and type I rhamnogalacturonan (RG-I) regions. Pectin HG regions consist of poly-galacturonic acid residues, which can be partially methyl-esterified. Pectins with a low degree of methyl esterification (DM) < 50% are known as low methoxyl (LM) pectins and are of particular interest in drug delivery as they can form gels with calcium ions (Ca2+), which has potential applications especially in nasal formulations. An outstanding example, of a delivery using pectin is now utilised (PecSys®) in a nasal product recently approved for commercial sale.

The stability (in terms of molar mass, viscosity and gel strength) of pectin formulations potentially plays an important role in their behaviour and functional properties in a wide range of applications and, therefore, any changes over time must be understood. Pectin depolymerise after prolonged storage periods and the rate of depolymerisation is greater at elevated temperatures (40 °C). This results in a decrease in the strength for LM pectin gels; although this decrease in gel strength does not appear to have a detrimental effect on the release of a model drug.