title: Isolation and characterisation of 13 pterosins and pterosides from bracken (Pteridium aquilinum (L.) Kuhn) rhizome.
abstract: Systematic phytochemical investigations of the underground rhizome of Pteridium aquilinum (L.) Kuhn (Dennstaedtiaceae) afforded thirty-five pterosins and pterosides. By detailed analysis of one- and two-dimensional nuclear magnetic resonance spectroscopy, circular dichroism (CD) and high-resolution mass spectrometric data, thirteen previously undescribed pterosins and pterosides have been identified. Interestingly, for the first time 12-O-β-D-glucopyranoside substituted pterosins, rhedynosides C and D, and the sulfate-containing pterosin, rhedynosin H, alongside the two known compounds, histiopterosin A and (2S)-pteroside A2, were isolated from the rhizomes of subsp. aquilinum of bracken. In addition, six-membered cyclic ether pterosins and pterosides, rhedynosin A and rhedynoside A, are the first examples of this type of pterosin-sesquiterpenoid. Additionally, the three previously reported compounds (rhedynosin I, (2S)-2-hydroxymethylpterosin E and (2S)-12-hydroxypterosin A) were obtained for the first time from plants as opposed to mammalian metabolic products. Single crystal X-ray diffraction analysis was applied to the previously undescribed compounds (2R)-rhedynoside B, (2R)-pteroside B and (2S)-pteroside K, yielding the first crystal structures for pterosides, and three known pterosins, (2S)-pterosin A, trans-pterosin C and cis-pterosin C. Rhedynosin C is the only example of the cyclic lactone pterosins with a keto group at position C-14. Six selected pterosins ((2S)-pterosin A, (2R)-pterosin B and trans-pterosin C) and associated glycosides ((2S)-pteroside A, (2R)-pteroside B and pteroside Z) were assessed for their anti-diabetic activity using an intestinal glucose uptake assay; all were found to be inactive at 300 μM.
authors.affiliation: School of Chemistry, Bangor University, Bangor LL57 2UW, UK.
authors.forename: Rizgar Hassan
authors.initials: RH
authors.lastname: Mohammad
authors.affiliation: School of Chemistry, Bangor University, Bangor LL57 2UW, UK; Department of Pharmacognosy, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Nur-E-Alam
authors.affiliation: School of Chemistry, Bangor University, Bangor LL57 2UW, UK.
authors.forename: Martina
authors.initials: M
authors.lastname: Lahmann
authors.affiliation: IBERS, Aberystwyth University, Penglais, Aberystwyth SY23 3DA, UK.
authors.forename: Ifat
authors.initials: I
authors.lastname: Parveen
authors.affiliation: UK National Crystallography Service, School of Chemistry, University of Southampton, University Road, Southampton SO17 1BJ, UK.
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Tizzard
authors.affiliation: UK National Crystallography Service, School of Chemistry, University of Southampton, University Road, Southampton SO17 1BJ, UK.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Coles
authors.affiliation: Strategic Science Group, Unilever R&D, Colworth Science Park, Bedford MK44 1LQ, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Fowler
authors.affiliation: Biomolecular Spectroscopy Centre, Pharmaceutical Optical & Chiroptical Spectroscopy Facility, King's College London, The Wolfson Wing, WWB10 Hodgkin Building, Guy's Campus, London SE1 1UL, UK.
authors.forename: Alex F
authors.initials: AF
authors.lastname: Drake
authors.affiliation: Manchester Institute of Biotechnology, University of Manchester, 131 Princess St, Manchester M1 7DN, UK.
authors.forename: Derren
authors.initials: D
authors.lastname: Heyes
authors.affiliation: School of Chemistry, Bangor University, Bangor LL57 2UW, UK. Electronic address: vera.thoss@bangor.ac.uk.
authors.forename: Vera
authors.initials: V
authors.lastname: Thoss
mesh_terms: D000818:Animals; D003920:Diabetes Mellitus / Q000188:drug therapy; D006027:Glycosides / Q000737:chemistry / Q000302:isolation & purification*; D007189:Indans / Q000737:chemistry / Q000302:isolation & purification*; D019906:Nuclear Magnetic Resonance, Biomolecular; D032498:Pteridium / Q000737:chemistry*; D027343:Rhizome / Q000737:chemistry*; D012717:Sesquiterpenes / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology
chemical_list: D006027:Glycosides; D007189:Indans; D012717:Sesquiterpenes; C010772:pterosin; C010771:pterosides
keywords: Bracken pterosins; Circular dichroism; Dennstaedtiaceae; Norsesquiterpenes; Pteridium aquilinum; Pterosides; Pterosins A and B; SGLT1 and GLUT2 transporters; Sesquiterpenoids