Disclosed herein are modified saponins or fractions thereof obtainable by modification of a crude Quillaja saponaria extract or by modification of purified saponins obtainable from a crude Quillaja saponaria extract useful in pharmaceutical compositions for enhancing the transport of pharmacologically active substances across mucous membranes of an animal. Also disclosed are modified saponins having reduced irritability wherein the aldehyde group is reduced and the fatty acid moiety may be removed by hydrolysis. Also disclosed are pharmaceutical compositions comprising the modified saponins of the invention.
