Gnetum leyboldii and G. schwackeanum (Gnetaceae) are lianas of Amazonia. The former contains in its wood the gnetins A,B,C,D and E for which the structures of rel-(1R,5R,6R,7R)-6-(4-hydroxyphenyl)-7-(3,5-dihydroxyphenyl)-3-(E)-(4-hydroxystyryl)-4,8-dioxobicyclo[3.2.1]oct-2-ene; 1-hydroxy-6-(4-hydroxyphenyl)-6-(3,5-dihydroxyphenyl)-3-(E)-(4-hydroxystyryl)-7-oxobicyclo[2.2.2]oct-2-ene; rel-(2S,3S)-4-hydroxy-2-(4-hydroxyphenyl)-3-(3,5-dihydroxyphenyl)-6-(E)-(4-hydroxystyryl)-2,3-dihydrobenzofuran; rel-(2S,3S)-4-hydroxy-2-(2,4-dihydroxyphenyl)-3-(3,5-dihydroxyphenyl)-6-(E)-(4-hydroxystyryl)-2,3-dihydrobenzofuran; and rel-(2S,3S)-4-hydroxy-2-(4-hydroxyphenyl)-3-[6-rel-(2S,3S)-4-hydroxy-2-(4-hydroxyphenyl)-3-(3,5-dihydroxyphenyl)-2,3-dihydrobenzofuranyl]-6-(E)-(4-hydroxystyryl)-2,3-dihydrobenzofuran were proposed, respectively. The fruits of G. schwackeanum contain the gnetins C and E. Of the 33 recognized Gnetum species, only 6 occur in tropical America, G. leyboldii Tull. being distributed towards the south of Amazonia mainly in marshy or periodically flooded regions and G. schwackeanum Taub. occurring throughout the State of Amazonas on "terra firme" (non-flooded ground) (2). An ethanol extract of the woody part of the former liana contained five novel compounds designated gnetins A to E. An acetone extract of the fruits of the latter liana contained the gnetins C and E.