Isoprenylated flavonoids—a survey

According to the traditional usage of the plant for antiinflammation and analgesia, Leucas aspera was tested for its prostaglandin (PG) inhibitory and antioxidant activities. The extract showed both activities, i.e., inhibition at 3 x 10(-4) g/ml against PGE(1)- and PGE(2)-induced contractions in guinea pig ileum and a 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging effect. The separation guided by the activities in these dual assay methods provided eight lignans and four flavonoids, LA-1- -12, among which LA-1- -7 and LA-10- -12 were identified as nectandrin B, meso-dihydroguaiaretic acid, macelignan, acacetin, apigenin 7-O-[6"-O-(p-coumaroyl)-beta-D-glucoside], chrysoeriol, apigenin, erythro-2-(4-allyl-2, 6-dimethoxyphenoxy)-1-(4-hydroxy-3-methoxyphenyl)propan-1-ol, myristargenol B, and machilin C, respectively. LA-8 was determined to be (-)-chicanine, the new antipode of the (+) compound, by spectroscopic methods including CD and ORD. Chiral-HPLC analysis of LA-9 showed that it was a mixture of two enantiomers, (7R, 8R)- and (7S, 8S)-licarin A. All of these components were first isolated from L. aspera. PG inhibition was observed in LA-1, LA-2, and LA-5, and antioxidant activity in LA-1- -3 and LA-8- -12.

Separation of Leucas aspera, a medicinal plant of Bangladesh, guided by prostaglandin inhibitory and antioxidant activities.

Carbon-13 nuclear magnetic resonance spectroscopy of flavonoid and isoflavonoid compounds

Lignans neolignans and norneolignans from krameria cystisoides

13C NMR shielding data for about 300 compounds are tabulated, and critical spectral features are discussed as a guide to the use of the technique in structure elucidation and stereochemical allocations of lignan, neolignan and their derivatives. Unanalysed reported data have been analysed and, wherever necessary, 13C signal assignments have been revised on the basis of more recent evidence and, to obtain consistency throughout the series.

Marilia O. da S. Pereira

Papers

13C NMR spectroscopy of neolignans

Prenylated flavonoids from seeds of Calopogonium mucunoides