Cardiovascular protective flavonolignans and flavonoids from Calamus quiquesetinervius

Tricin-type flavonolignans, (2S)-dihydrotricin 4'-O-(erythro-beta-guaiacylglyceryl) ether, (2S)-dihydrotricin 4'-O-(threo-beta-guaiacylglyceryl) ether, (2S)-dihydrotricin 4'-O-(threo-beta-4-hydroxyphenylglyceryl) ether, tricin 4'-O-(erythro-beta-4-hydroxyphenylglyceryl) ether, tricin 4'-O-(threo-beta-4-hydroxylphenylglyceryl) ether, and (2S)-dihydrotricin 4'-O-(beta-6''-methoxy-4''-oxo-chroman-3''-yloxy) ether namely calquiquelignan A-F, respectively, were isolated and characterized from the EtOAc extract of Calamus quiquesetinervius. Additionally, six known phenolic compounds, including dihydrotricin, tricin, salcolin A, p-hydroxybenzoic acid, (2S, 3S)-trans-dihydrokapempferol and (2S)-naringenin, were also obtained and identified from the extract. Structures of the flavonolignans were assigned based on spectroscopic analyses that included 1D and 2D NMR spectroscopic techniques, such as HMQC, HMBC, and NOESY. Bioassay results showed that calquiquelignan A, dihydrotricin and (2S)-naringenin exhibited significant vasodilatory potencies, as indicated by 60.3%, 80.3% and 60.9% relaxations, respectively, at 100 microM. Salcolin A showed potent platelet aggregation inhibition, compared with aspirin. Most of the tricin-type derivatives (calquiquelignan A-B, dihydrotricin and tricin) also exhibited more potent hydroxyl radical ((.)OH) scavenging activity than trolox as characterized by the ultraweak chemiluminescence assay.