Question: will disaccharides and polysaccharides give a positive result for molisch test

Answer: Yes, All carbohydrates -- monosaccharides, disaccharides, and polysaccharides -- should give a positive reaction, and nucleic acids and glycoproteins also give a positive reaction, as all these compounds are eventually hydrolyzed to monosaccharides by strong mineral acids. Pentoses are then dehydrated to furfural, while hexoses are dehydrated to 5-hydroxymethylfurfural. Either of these aldehydes, if present, will condense with two molecules of naphthol to form a purple-colored product, as illustrated below by the example of glucose: