A simple, two-step, procedure has been developed to purify antidiabetic compounds from Eugenia jambolana fruit-pulp. The compounds have been identified as a peptidylglycan and an oligosaccharide with molecular weights of 6.0 and 1.2 kD, respectively. The binding between the sugars and the peptide in the peptidylglycan appears to be covalent. The amino acid and sugar composition of the peptidylglycan have been determined as have the sugars of the oligosaccharide. The intrinsic color of the peptidylglycan was attributed to the compound itself and not to the presence of pigment or metal. The peptidylglycan was resistant to degradation by proteolytic enzymes in vitro, explaining its efficacy in oral feeding.