Isoflavonoids of the leguminosae

Carbon-13 with a natural abundance of only 1.1% and a smaller magnetic moment than 1H (and hence a weaker NMR signal) was for many years a nucleus relatively inaccessible to NMR spectroscopists. However, with the advent in recent years of pulsed NMR and Fourier Transform (FT) analysis, 13C-NMR spectroscopy has become more readily available. As a result the past five years have seen a dramatic increase in the number of publications on, or involving, 13C-NMR spectroscopy of flavonoids. For example major compilations include those of Ternai and Markham (1976), Markham and Ternai (1976), Markham et al. (1978), Wagner et al. (1976), Chari et al (1977a), Pelter et al (1976) and Wenkert and Gottlieb (1977). The increasing availability and sensitivity of modern FT-NMR spectrometers is assurance that this powerful technique will become a major tool for the structure elucidation of flavonoids and their glycosides.

Carbon-13 NMR Spectroscopy of Flavonoids

Isoprenylated flavonoids—a survey

Lignans and norlignans constitute abundant classes of phenylpropanoids. Biosynthesis of these compounds has received widespread interest, mainly because they have various clinically important biological activities. In addition, lignans and norlignans are often biosynthesized and deposited in significant amounts in the heartwood region of trees as a metabolic event of heartwood formation, probably preventing heart rot by heart-rot fungi. Furthermore, biosynthetic reactions of lignans and norlignans involve unique stereochemical properties that are of great interest in terms of bioorganic chemistry and are expected to provide a model for biomimetic chemistry and its application. We outline the recent advances in the study of lignan and norlignan biosynthesis.

/pdf/biosynthesis-of-lignans-and-norlignans-38qinfj1co.pdf

Biosynthesis of lignans and norlignans

A meroterpene and four flavonoids were isolated from the seeds of Psoralea corylifolia as antioxidative components. Their structures were elucidated by spectral data and identified as bakuchiol (1), bavachinin (2), bavachin (3), isobavachin (4) and isobavachalcone (5). In particular, meroterpene 1 and flavonoids 4 and 5 showed broad antioxidative activities in rat liver microsomes and mitochondria. They inhibited NADPH-, ascorbate-, t-BuOOH- and CCl(4)-induced lipid peroxidation in microsomes. They also prevented NADH-dependent and ascorbate-induced mitochondrial lipid peroxidation. Bakuchiol (1) was the most potent antioxidant in microsomes and the inhibition of oxygen consumption induced by lipid peroxidation was time-dependent. Furthermore, bakuchiol (1) protected human red blood cells against oxidative haemolysis. These phenolic compounds in P. corylifolia were shown to be effective in protecting biological membranes against various oxidative stresses.

Antioxidative components of Psoralea corylifolia (Leguminosae).

Two new benzofuran derivatives [I], mp 235-237°, C15H10O5 and [II], mp 179-181°, C16H12O5, together with l-maackiain, stigmasterol, medicagol, formononetin and 2', 4', 4-trihydroxychalone (isoliquirtigenin) were isolated from the aerial parts of Sophora tomentosa L., and the structures of I and II were established to be 2-(2', 4'-dihydroxyphenyl)-5, 6-methylenedioxybenzofuran and 2-(2'-hydroxy-4'-methoxyphenyl)-5, 6-methylenedioxybenzofuran on the bases of chemical and spectral evidence, respectively.

Studies on the Constituents of Sophora Species. XII. Constituents of the Aerial Parts of Sophora tomentosa L. (1)

Two prenylflavanones from Euchresta japonica

Two flavanones in Sophora leachiano and some related structures

Isoflavonoids from Sophora secundiflora, S. arizonica and S. gypsophila

A new flavanone, named euchrestalfavanone A (I), mp 145-147°C, C25H28O5, was isolated from the root of Euchresta japonica HOOK. f. ex REGEL (Leguminosae) together with l-maackiain, medicagol and trifolirhizin. The structure of I was established to be 6, 3'-di-γ, γ-dimethylallyl-5, 7, 4'-trihydroxyflavanone on the basis of chemical and spectral evidence.

Manki Komatsu

Papers

Studies on the Constituents of Sophora Species. XII. Constituents of the Aerial Parts of Sophora tomentosa L. (1)

Two prenylflavanones from Euchresta japonica

Two flavanones in Sophora leachiano and some related structures

Isoflavonoids from Sophora secundiflora, S. arizonica and S. gypsophila

Studies on the Constituents of Sophora Species. XVI. Constituents of the Root of Euchresta japonica HOOK. f. ex REGEL (1)