Methylated flavonols in Larrea cuneifolia

Abstract

Nine of eleven methylated flavonols isolated from Larrea cuneifolia Cav. collected in Argentina have been fully characterized. UV, MS and NMR spectral data are presented for the nine substances all of which were identified as methyl ethers of quercetin and kaempferol. Two of the compounds, 7,3′,4′-trimethylquercetin (II) and 3,7,3′-trimethylquercetin (III), are new natural products. The others are 3,7,3′,4′-tetramethylquercetin (I) (retusine), 3,7-dimethylkaempferol (IV), 7,3′-dimethylquercetin (V) (rhamnazin), 3,7-dimethylquercetin (VI) (kumatakenin), 3,3′-dimethylquercetin (VII), 3-methylkaempferol (VIII) and 3′-methylquercetin (IX) (isorhamnetin). Nordihydroguaiaretic acid (XII) was also detected.