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

• Published in: Phytochemistry (Oxford) 2003-07, Vol.63 (5), p.589-595
• Main Author: Markham, Kenneth R.
• Format: Article
• Language: English
• Subjects: 6-Methoxyluteolin 7, 4′- O-glycosides; Biological and medical sciences; Chemical constitution; Flavone penta- and hexa- O-glycosides; Flavone-polysaccharide; Flavonoids - chemistry; Freshwater; Fundamental and applied biological sciences. Psychology; Glycosides - chemistry; Hepatophyta - chemistry; Hepatophyta - classification; Liverwort; Magnetic Resonance Spectroscopy; Mass Spectrometry; Molecular Structure; Monoclea forsteri; Monocleales; Plant physiology and development; Polysaccharides - chemistry
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/S0031-9422(03)00199-7

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. The “flavone-polysaccharide” (MF-1) from the liverwort, Monoclea forsteri, is shown to be a mixture of penta- and hexa- O-glycosides of 6-methoxyluteolin, and luteolin. MF-1a is 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 its de-arabinosyl equivalent. These are the first flavone penta- and hexa-glycosides to be described.