Prenylated stilbenes from peanut root mucigel

Authors: Sobolev, Victor; Potter, Thomas; Horn, Bruce

Submitted to: Phytochemical Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2005
Publication Date: 6/30/2006
Citation: Sobolev, V., Potter, T.L., Horn, B.W. 2006. Prenylated stilbenes from peanut root mucigel. Phytochemical Analysis. 17:312-322.

Interpretive Summary: Root tips of many plant species are covered with a layer of slime called mucigel, which mechanically protects and lubricates the roots as they grow between soil particles. Mucigel favors development of mycorrhizae (beneficial root-fungus associations), enhances nutrient and water absorption from the soil, promotes soil aggregation, and reduces root desiccation during drought. We hypothesized that mucigel may also serve as a chemical shield to protect the growing root from pathogenic molds and bacteria. The purpose of this work was to characterize defensive chemicals in peanut root mucigel under controlled conditions. The research demonstrated that peanut mucigel contains phytoalexins similar to ones that are produced by peanut kernels when challenged by fungi. Phytoalexins are relatively simple chemicals that inhibit the growth of invading microorganisms. The tentative structures of the 8 new mucigel phytoalexins were elucidated with the help of modern analytical techniques. The major phytoalexin in mucigel was present at several hundred times the concentration of similar known phytoalexins in other parts of the peanut plant.

Technical Abstract: Root tips of many plant species are covered with a layer of slime called mucigel, which mechanically protects and lubricates the roots as they grow between soil particles. Mucigel favors development of mycorrhizae, enhances nutrient absorption from the soil, promotes soil aggregation, and reduces root desiccation during drought. We hypothesized that mucigel contains phytoalexins and serves as a chemical shield to protect the growing root from soil pathogens. The research demonstrated that peanut (Arachis hypogaea) root mucigel contains at least 8 new prenylated stilbenes; tentative structures were elucidated for seven of these. The major stilbenoid was named mucigelin and assigned the structure of 4-(3-methyl-but-1-enyl)-3,5-dimethoxy-4'-hydroxy-trans-stilbene on the basis of MSn and UV spectroscopic evidence. Mucigelin concentration in the mucigel averaged 40 ppm under axenic conditions, which was several hundred times the concentration of known stilbenoids in other structures of the peanut plant under similar conditions. The new stilbenoids were detected only in the mucigel.