title: Manninotriose is a major carbohydrate in red deadnettle (Lamium purpureum, Lamiaceae).
abstract: OBJECTIVE
  There is a great need to search for natural compounds with superior prebiotic, antioxidant and immunostimulatory properties for use in (food) applications. Raffinose family oligosaccharides (RFOs) show such properties. Moreover, they contribute to stress tolerance in plants, acting as putative membrane stabilizers, antioxidants and signalling agents.
  
  
  METHODS
  A large-scale soluble carbohydrate screening was performed within the plant kingdom. An unknown compound accumulated to a high extent in early-spring red deadnettle (Lamium purpureum) but not in other RFO plants. The compound was purified and its structure was unravelled with NMR. Organs and organ parts of red deadnettle were carefully dissected and analysed for soluble sugars. Phloem sap content was analysed by a common EDTA-based method.
  
  
  RESULTS
  Early-spring red deadnettle stems and roots accumulate high concentrations of the reducing trisaccharide manninotriose (Galα1,6Galα1,6Glc), a derivative of the non-reducing RFO stachyose (Galα1,6Galα1,6Glcα1,2βFru). Detailed soluble carbohydrate analyses on dissected stem and leaf sections, together with phloem sap analyses, strongly suggest that stachyose is the main transport compound, but extensive hydrolysis of stachyose to manninotriose seems to occur along the transport path. Based on the specificities of the observed carbohydrate dynamics, the putative physiological roles of manninotriose in red deadnettle are discussed.
  
  
  CONCLUSIONS
  It is demonstrated for the first time that manninotriose is a novel and important player in the RFO metabolism of red dead deadnettle. It is proposed that manninotriose represents a temporary storage carbohydrate in early-spring deadnettle, at the same time perhaps functioning as a membrane protector and/or as an antioxidant in the vicinity of membranes, as recently suggested for other RFOs and fructans. This novel finding urges further research on this peculiar carbohydrate on a broader array of RFO accumulators.
authors.affiliation: Laboratory of Molecular Plant Biology, KU Leuven, Kasteelpark Arenberg 31, B-3001 Leuven, Belgium.
authors.forename: Raquel
authors.initials: R
authors.lastname: dos Santos
authors.forename: Rudy
authors.initials: R
authors.lastname: Vergauwen
authors.forename: Pieter
authors.initials: P
authors.lastname: Pacolet
authors.forename: Eveline
authors.initials: E
authors.lastname: Lescrinier
authors.forename: Wim
authors.initials: W
authors.lastname: Van den Ende
mesh_terms: D001692:Biological Transport; D004492:Edetic Acid; D019686:Lamiaceae / Q000737:chemistry* / Q000502:physiology; D009682:Magnetic Resonance Spectroscopy; D009844:Oligosaccharides / Q000737:chemistry; D052585:Phloem / Q000737:chemistry; D053147:Plant Exudates / Q000032:analysis / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry / Q000187:drug effects; D018517:Plant Roots / Q000737:chemistry; D018547:Plant Stems / Q000737:chemistry*; D011887:Raffinose / Q000737:chemistry; D012621:Seasons; D012995:Solubility; D013045:Species Specificity; D014312:Trisaccharides / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D009844:Oligosaccharides; D053147:Plant Exudates; D014312:Trisaccharides; C069155:manninotriose; C005695:stachyose; D004492:Edetic Acid; D011887:Raffinose