Raffinose family oligosaccharides (RFOs) are ubiquitous in higher plants and function as transport compounds, and are also involved in stress tolerance mechanisms and perhaps also signalling processes. Santos et al. screen more than 100 species and find an unknown compound that accumulates significantly in early-spring plants of Lamium purpureum (red deadnettle, Lamiaceae). Using NMR, they determine it to be manninotriose (Gala1,6Gala1,6Glc), a derivative of the non-reducing RFO stachyose. They propose that manninotriose represents a temporary storage carbohydrate, 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.
