Isolation and characterisation of 13 pterosins and pterosides from bracken (Pteridium aquilinum (L.) Kuhn) rhizome

  • Phytochemistry. 2016 Aug:128:82-94. doi: 10.1016/j.phytochem.2016.05.001.
Rizgar Hassan Mohammad  1 ,  Mohammad Nur-E-Alam  2 ,  Martina Lahmann  1 ,  Ifat Parveen  3 ,  Graham J Tizzard  4 ,  Simon J Coles  4 ,  Mark Fowler  5 ,  Alex F Drake  6 ,  Derren Heyes  7 ,  Vera Thoss  8
Affiliations
  • 1. School of Chemistry, Bangor University, Bangor LL57 2UW, UK.
  • 2. 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.
  • 3. IBERS, Aberystwyth University, Penglais, Aberystwyth SY23 3DA, UK.
  • 4. UK National Crystallography Service, School of Chemistry, University of Southampton, University Road, Southampton SO17 1BJ, UK.
  • 5. Strategic Science Group, Unilever R&D, Colworth Science Park, Bedford MK44 1LQ, UK.
  • 6. 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.
  • 7. Manchester Institute of Biotechnology, University of Manchester, 131 Princess St, Manchester M1 7DN, UK.
  • 8. School of Chemistry, Bangor University, Bangor LL57 2UW, UK. Electronic address: [email protected].
PMID: 27177933 DOI: 10.1016/j.phytochem.2016.05.001
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.

Keywords
Bracken pterosins; Circular dichroism; Dennstaedtiaceae; Norsesquiterpenes; Pteridium aquilinum; Pterosides; Pterosins A and B; SGLT1 and GLUT2 transporters; Sesquiterpenoids.
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