Phenylethanoid glycosides in tepals of Magnolia salicifolia and their occurrence in flowers of Magnoliaceae

• Published in: Phytochemistry (Oxford) 2015-09, Vol.117, p.185-193
• Main Authors: Porter, Elaine A., Kite, Geoffrey C., Veitch, Nigel C., Geoghegan, Ivey A., Larsson, Sonny, Simmonds, Monique S.J.
• Format: Article
• Language: English
• Subjects: Chemosystematics; Flower; Flowers - chemistry; Glycosides - chemistry; Glycosides - isolation & purification; Liriodendron; Magnolia salicifolia; Magnoliaceae; Magnoliaceae - chemistry; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Phenylethanoid glycosides; Phenylethyl Alcohol - analogs & derivatives; Phenylethyl Alcohol - chemistry; Phenylethyl Alcohol - isolation & purification; Xylose; Yulanoside A
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2015.02.025

Yulanosides A and B and 2′-rhamnoechinacoside were characterised from tepals of Magnolia salicifolia together with the known phenylethanol glycosides crassifolioside, echinacoside and verbascoside. Yulanosides are characteristic of Magnolia subgenus Yulania. •Phenylethanoid glycosides are abundant UV absorbing compounds in flowers of Magnolia.•Five novel phenylethanoid glycosides described from tepals of Magnolia salicifolia.•First description of a phenylethanoid pentaglycoside, yulanoside A.•Yulanoside A is a characteristic component of the tepals of Magnolia subgenus Yulania. Phenylethanoid glycosides were among the major UV-absorbing components in 80% aq. CH3OH extracts of the tepals of Magnolia salicifolia (Siebold & Zucc.) Maxim. (Magnoliaceae; Magnolia subgenus Yulania). Structural characterisation of isolated compounds by spectroscopic and chemical methods revealed three previously unrecorded examples, yulanoside A, yulanoside B and 2′-rhamnoechinacoside, and the known compounds echinacoside and crassifolioside; chromatographic methods also identified verbascoside in the tepal extract. Yulanoside A is the first reported example of a phenylethanoid pentaglycoside, namely hydroxytyrosol 1-O-{β-d-glucopyranosyl-(1→4)-β-d-glucopyranosyl-(1→6)-[3,4-dihydroxycinnamoyl-(→4)][α-l-rhamnopyranosyl-(1→3)][α-l-rhamnopyranosyl-(1→2)]-β-d-glucopyranoside}. A survey of Magnolia sensu lato and Liriodendron (the two genera of Magnoliaceae) suggested that yulanoside A and its deglucosyl derivative (yulanoside B) were a feature of the tepal chemistry of Magnolia subgenus Yulania (except Magnolia acuminata, the sole member of section Tulipastrum, which did not accumulate phenylethanoid glycosides). The two species of Liriodendron and examined examples of Magnolia subgenus Magnolia sections Magnolia and Rytidospermum (subsection Oyama) also accumulated phenylethanoid glycosides in their tepals and in these species, and in subgenus Yulania, the major compounds were one or more of echinacoside, 2′-rhamnoechinacoside, crassifolioside and verbascoside. Levels of phenylethanoid glycosides were found to be much lower in species studied from Magnolia sections Gwillimia, Macrophylla and Rytidospermum (subsection Rytidospermum), although yulanoside A was detectable in M. macrophylla and this may have some bearing on the placement of section Macrophylla, which is currently uncertain. In the isolates of yulanoside B and echinacoside, minor phenylethanoid glycosides were determined