Chemical characterization of the mucilage from fruits of Opuntia ficus indica

Extraction of peeled fruits of Opuntia ficus indica afforded with 3.8% yield a mucilage, which contained 23.4% of galacturonic acid. Total hydrolysis of a mucilage and gas–liquid chromatographic analysis of the derived alditol acetates indicated the presence of arabinose, rhamnose, xylose and galactose in the molar ratio 1.0:1.7:2.5:4.1. Gel permeation chromatography on Sepharose CL-4B showed the polysaccharide to be composed of at least five fractions. Treatment with cetrimide allowed the separation of an insoluble fraction (44.3% yield), which contained 28.0% of uronic acid. This fraction contained xylose, rhamnose and galactose in the molar ratio 1.0:2.5:2.8. The fraction soluble in cetrimide (15.6% yield) contained 16.0% uronic acid, and arabinose and galactose in the molar ratio of 1:2.2. It is composed of two main subfractions as shown by gel permeation chromatography. These results indicate that the mucilage from fruits O. ficus indica is a complex mixture of polysaccharides, less than 50% corresponding to a pectin-like polysaccharide.