6-Methoxyflavonoids and Other Constituents from Microliabum polymnioides (Asteraceae)

Abstract

The flower heads of Microliabum polymnioides afforded scopoletin, 5,4′-dihydroxy-3,6,7-trimethoxyflavone, 3,5,4′-trihydroxy-6,7-dimethoxyflavone and 3,5,7,4′-tetrahydroxy-6-methoxyflavone. The leaves contained hexadecanoic acid, phytol and docosane. This is the first report on the presence of 6-methoxy-flavonoids in Microliabum genus.

Methoxy 13C NMR Chemical Shift as a Molecular Descriptor in the Structural Analysis of Flavonoids and Other Phenolic Compounds

“…35 Based on several publications related to polymethoxylated flavonoids, it can be observed that OMe signals can be observed as independent and/or overlapping signals appearing in the 3.85 ± 0.25 ppm range in 1 H NMR spectra and their chemical shifts seem not to be very clearly correlated with the oxygenation pattern on the flavonoid nuclei. 8,22,[34][35][36][37][38][39][40][41][42][43][44] The next major advancement in flavonoid structural techniques was the application of homonuclear ( 1 H-1 H) and heteronuclear ( 1 H-13 C) correlation 2-dimensional-NMR spectroscopy. In 1 H-1 H correlation (COSY) spectroscopy, correlations are observed among chemical shifts of 1 H NMR resonances which are coupled with each other via J-couplings.…”

“…35 Based on several publications related to polymethoxylated flavonoids, it can be observed that OMe signals can be observed as independent and/or overlapping signals appearing in the 3.85 ± 0.25 ppm range in 1 H NMR spectra and their chemical shifts seem not to be very clearly correlated with the oxygenation pattern on the flavonoid nuclei. 8,22,34–44…”