wherein r 1 and r 2 are alkyl , aralkyl or aryl having up to 10 carbon atoms ; and a and b may be the same or different and are integers from 1 to 8 ; or a salt thereof with a pharmaceutically acceptable acid . anti - neoplastic , anti - diarrheal , anti - peristaltic , gastro - intestinal anti - spasmodic , anti - viral , anti - retroviral , anti - psoriasis and insecticidal compositions comprising biologically effective amounts of the above - described amines and biologically acceptable carriers therefor are also disclosed , as well as methods of treatment , administration or application of biologically effective amounts of the polyamines of the invention . also disclosed are methods for preparing the polyamines of the invention .