Extracts prepared from dried or fresh skins of 52 African amphibian species, other than bufonids, were subjected to chemical (colour reactions) and biological screening, to determine occurrence and contents of aromatic biogenic amines and peptides active on smooth muscle preparations and blood pressure. 2. Only indolealkylamines were detectable in the skins. They were represented by 5-hydroxytryptamine, its N-methylated derivatives and tryptamine. The indolealkylamines considered included the alkaloid trypargine, a carboline derivative resulting from the condensation of tryptamine with arginine. 3. The peptide families identified in skin extracts of the African frogs were as follows: caeruleins (caerulein, [Asn2, Leu5] caerulein), tachykinins (kassinin, [Glu2, Pro5] kassinin, hylambatin), bradykinins [( Hyp3] bradykinin), xenopsin, thyrotropin releasing hormone, peptide PYLa and the magainins I and II. The last five peptides have been so far identified only in the skin of Xenopus laevis, together with their precursors. 4. Since numerous other peptide molecules await isolation, elucidation of structure, and definition of possible biological activities, the array of peptides occurring in the skin of African amphibians, as in that of Australian and American amphibians, is destined to increase.
