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A “flavone-polysaccharide” redefined as a mixture of 6-methoxyluteolin penta- and hexa-O-glycosides

2003; Elsevier BV; Volume: 63; Issue: 5 Linguagem: Inglês

10.1016/s0031-9422(03)00199-7

1873-3700

Kenneth R. Markham,

Lichen and fungal ecology

The incomplete structure proposed in 1972 for a unique “flavone-polysaccharide” compound, MF-1, from the liverwort Monoclea forsteri, has been re-examined. Rather than the proposed 8-methoxyluteolin structure with polysaccharides attached to the 7- and 4′-hydroxyls, MF-1 has been shown to be primarily a mixture of penta- and hexa-O-glycosides of 6-methoxyluteolin, which are accompanied by their luteolin analogues. MS and NMR evidence is marshalled to define the structure of MF-la as 6-methoxyluteolin 7-O-[2-O-α-rhamnosyl-3-O-α-arabinosyl-β-glucuronide]-4′-O-[2-O-α-rhamnosyl-3-O-β-xylosyl-β-glucuronide], and MF-1b as 6-methoxyluteolin 7-O-[2-O-α-rhamnosyl-β-glucuronide]-4′-O-[2-O-α-rhamnosyl-3-O-β-xylosyl-β-glucuronide]. This report is the first to provide substantive evidence for the existence of flavone penta- and hexa-O-glycosides in nature. The newly defined structure(s) for MF-1 more closely align M. forsteri with the only other species in the order Monocleales, M. gottschei.