Studies on Nepalese Crude Drugs. XIV. New Flavonoids from the Root of Scutellaria prostrata Jacq. ex Benth.
Abstract
Six flavonoids, named scutellaprostins A, B, C, D, E and F, were isolated from teh root of Scutellaria prostrata JACQ. ex BENTH. (Labiatae). Their structures were established to be (2R*, 3R*)-6-hydroxy-3-(4-hydroxy-3-methoxyphenyl)-2-hydroxymethyl-9-phenyl-2, 3-dihydro-7H-1, 4-dioxino[2, 3-h]chromene-7-one (I), (2R*, 3*)-6-hydroxy-3-(4-hydroxy-3-methoxyphenyl)-2-hydroxymethyl-9-(4-hydroxyphenyl)-2, 3-dihydro-7H-1, 4-dioxino[2, 3-h]-chromene-7-one (II), (2R*, 3R*)-6-hydroxy-3-(4-hydroxy-3-methoxyphenyl)-2-hydroxymethyl-9-(3, 4-dihydroxyphenyl)-2, 3-dihydro-7H-1, 4-dioxino-[2, 3-h]chromene-7-one (III), (2R*, 3R*)-5-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-8-phenyl-2, 3-dihydro-6H-1, 4-dioxino-[2, 3-g]chromene-6-one (IV), (2R*, 3R*)-5-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-8-(4-hydroxyphenyl)-2, 3-dihydro-6H-1, 4-dioxino[2, 3-g]chromene-6-one (V) and (2R*, 3R*)-5-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-8-(3, 4-dihydroxyphenyl)-2, 3-dihydro-6H-1, 4-dioxino[2, 3-g]chromene-6-one (VI), respectively, by chemical and spectral data. They were synthesized by oxidative coupling of the flavones and coniferyl alcohol in the presence of silver oxide.