QUANTIFICATION OF SAPONINS IN AERIAL AND SUBTERRANEAN TISSUES OF MEDICAGO TRUNCATULA

Authors: HUHMAN, DAVID - SAMUEL ROBERTS NOBLE FOUN; Berhow, Mark; SUMNER, LLOYD - SAMUEL ROBERTS NOBLE FOUN

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2005
Publication Date: 2/12/2005
Citation: Huhman, D.V., Berhow, M.A., Sumner, L.W. 2005. Quantification of saponins in aerial and subterranean tissues of medicago truncatula. Journal of Agricultural and Food Chemistry. 53:1914-1920.

Interpretive Summary: Medicago truncatula is small plant related to soybeans, alfalfa, and other legume plants which can be rapidly grown in the laboratory and used as a model system to study phytochemicals. The saponins are biologically active compounds found in most legumes including Medicago truncatula. The accumulation of these compounds in the roots, shoots, leaves, flowers and seeds was studied to assess how plants make and store saponins. It was determined that the plant accumulated one type of saponin in the leaves and seeds, and a different type in the roots. This may likely reflect the different functions these compounds play in protecting the plant from predators, the ones in the leaves protect from insect attack, those in the roots from fungal attack. These basic studies will allow for a better understanding of how these important nutritional and pesticidal compounds are made in the plant.

Technical Abstract: Trieterpene saponins from aerial and subterranean tissues of Medicago truncatula, cv. Jemalong A-17, were qualitatively profiled and quantified using reverse-phase HPLC with on-line photodiode array detection and electrospray-ionization mass spectrometry (HPLC/PDA/ESI/MS). Absolute quantifications were performed for 3-Glc-medicagenic acid and soyasaponin 1 (3-Rha-Gal-GlcA-soyasapogenol B); whereas, relative quantifications were determined for twenty-nine other saponins in root and seventeen in leaf. Roots contained the greatest total amount of saponins followed by leaf and seed respectively. The quantitative data also reveal the differential accumulation of triterpene saponins in the various organs of M. truncatula. Specifically, relatively higher quantities of medicagenic acid conjugates accumulated in leaf and seed; whereas, relative higher levels of soysapogenol conjugates were observed in root. The differential accumulation of specific triterpene saponins is suggestive of spatially differentiated biosynthesis and/or biological function.