A new C-Glycosylflavone from Encyclia michuacana

The methanol extracts from Encyclia michuacana tubercles yielded the new 8-C-(6-deoxy-β-d-glucopyranosyl)apigenin (1) together with known 1-(3′-hydroxy-5′-methoxyphenyl)-2-(4″-hydroxy-5″-methoxyphenyl)ethane (2) and 2-(4-hydroxybenzyl)malic acid (3). The new structure was elucidated using spectroscopic methods, mainly 1D and 2D NMR. The β-anomer for 1 was supported by comparison of the experimental 1H–1H coupling constant values with those generated employing a generalized Karplus-type relationship using dihedral angles extracted from DFT calculations.