Bioactive alginates

• Main Author: Wilcox, Matthew David
• Published: University of Newcastle Upon Tyne 2010
• Subjects: 572.566
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578262

Alginates are polysaccharides extracted from the cell walls of brown seaweed or from certain bacteria such as Azotobacter vinelandii. Alginates have been shown to reduce the activity of pepsin and initial data suggest that it may affect the activity of pancreatic lipase. Pancreatic lipase plays an important role in the breakdown of triacylglycerol, if the activity of pancreatic lipase can be reduced then the breakdown of triacylglycerol would be reduce which in turn would lower the amount absorbed by the body. A pharmaceutical treatment for obesity called orlistat inhibits lipase and accounts for 66% of all prescriptions for treatments for obesity in 2008 in the UK. However the side effects of orlistat (uncontrolled diarrhoea and steatorrhea) can reduce the compliance with the treatment. If orlistat is taken with a high fibre product it has been shown that this can greatly reduce or eliminate the side effects. Since alginate is a dietary fibre it is believed that this could be an effect treatment for obesity. Colourimetric and turbidimetric assays were used to determine the effect of a wide range of alginates and other dietary fibres on pancreatic lipase. Alginates have the ability to inhibit pancreatic lipase, with a maximum inhibition of 72.2% (±9.9). Pectin could also inhibit lipase by a maximum of 71.8% (±22.3), however, specific enzymactically modified alginates could activate the enzyme by up to 22.0% (±10.1). Carrageenan and Hydroxypropyl methylcellulose could also activate the enzyme by a maximum of 37.3% (±24.5). The structure of the alginate is key to the inhibition or activation of the enzyme. Consecutive guluronate residues are important for inhibition whereas alternating mannuronate and guluronate blocks are detrimental to inhibition. The alginate that activated the enzyme was almost entirely consisting of poly-alternating uronate residues. The level of esterification was important for pectins inhibition of lipase with higher levels causing little inhibition. Alginate causes sustained inhibition at low concentrations of biopolymer compared to pectin. Therefore alginate could play a potential role in the management of obesity. ii