A new dimeric stilbene, the name for which is suggested as maackin A, is isolatedfi'om the wood of Maackia amurensis. The stlTicture of maackin A is determined by NMR. UV. and IR spectral methods. The cis-isomers that are observed during fractionation of the extracts are not native components of the wood but are formed from the trans-dimers under certain separation conditions.We have previously reported the chemical components in alcohol extracts of the heartwood ofMaackia amurensis. In addition to isoflavones and monomeric stilbenes [1 ], their addition product, isoflavonostilbene [2], dimeric stilbenes [3], and stilbenolignan [41 were also isolated. Multiple chromatography on silica-gel columns in various solvent systems was used.Separation of the fraction with dimeric stilbenes enabled the identification of three compounds: scirpusin A, scirpusin B, and maackin. However, difficulties arising during further investigations of the polar fractions of the extracts prompted us to .seek new approaches lbr studying their composition. Reverse-phase chromatography on C-18 silica gel in aqueous methanol acidified with formic acid was rather effective for preparative separation of the dimeric stilbenes that we obtained earlier and for the detection of a new compound, a structural isomer of scirpusin B, for which we propose the name maackin A (1). The separation procedure also revealed and isolated cis-isomers of these dimers according to UV and PMR spectral data.The question of whether the cis-derivatives are native remained unanswered because the methods available to us for analyzing the initial extract were not able unambiguously to establish their presence or absence.The goal of the present investigation was to determine if the dimeric cis-stilbenes that are observed in the alcohol extracts of Maackia amurensis heartwood are native. The structure of a new dimeric stilbene was also determined.The presence of cis-stilbenes in plants was first reported in 1962. However, the only reliable source of cis-resveratroi was for a long time Eucalypttts wandoo [51. The question of whether cis-stilbenes are present in various plant materials continues to be debated today. Natural substrates are suggested to occur in nature, as a rule, as the more stable trans-isomers. Reports describing the simultaneous presence in plants of monomeric cis-and trans-stilbenes began to appear in 1976. Thus, cis-"and trans-resveratroi was observed in peanuts [6]. Later, polyhydroxylated cis-and trans-stilbenes were isolated from the stems of Phoenix dactilifera [71. Rhubarb root (Rhei rhizoma Polygonaceae) yielded five monomeric cis-stilbenes in 1984 [8].The cis-and trans-isomers of 3,4',5-trimethoxystilbene were lbund in Fer, da latipinna [9].A series of monomeric cis-stilbenes named combretastatins was isolated from woody African plants of the Combretaceae family. The first representative is combretastatin A-1 from Combretum caffrum [ 10], which is especially interesting because it actively inhibits the ffowth ofP-388 lymphatic leukemia tumor cells....
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