N-1,N-5,N-10-tris(4-hydroxycinnamoyl)spermidines from Microdesmis keayana roots

Three new N-1,N-5,N-10-tris(4-hydroxycinnamoyl)spermidines were isolated from a methanolic root extract of Microdesmis keayana. They were identified as N-5,N-10-di(p-coumaroyl)-N-1-feruloylspermidine, N-5-(p-coumaroyl)-N-1,N-10-diferutoyispermidine, and NI,N5,N-10-triferuloylspermidine, and were named keayanidines A, B, and C (1-3), respectively. Their structures were established by spectral techniques (electrospray mass spectrometry, one- and two-dimensional NMR.). A 4',4,4'-trimethylated derivative was prepared by methylation of keayanidine Q and the same compound was synthesized from spermidine and 3,4-dimethoxycinnamic acid to confirm the spectral attributions of the NMR data of the natural compounds. Radical-scavenging properties of all compounds were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical spectrophotometric assay.