tomato plants for resistance against for example the Colorado beetle and to snails. It is also a defense against fungi. Membrane disruption The membrane disruptive properties of tomatine are caused by the ability to form 1:1 complexes with cholesterol. A possible mechanism of the membrane disruption by glycoalkaloids is displayed in figure 2. First, the aglycon part of tomatine binds reversibly to sterols in the membrane (figure 2, part 2). When this reaches a certain density, the glycosidic residues of the glycoalkaloids interact with each other by electrostatic interactions. This interaction catalyzes the development of an irreversible matrix of glycoalkaloid-sterol complexes (figure 2, part 4). In this way, the sterols from the external membrane are immobilized and membrane budding will arise. Tubular structures are formed, because of the structure of tomatine (figure 2, part 6). This membrane disruption causes cell death by cell leakage. Also, the disrupted membrane has an influence on sodium transport, by altering the membrane potential and reducing active sodium transport. When tomatine is orally ingested, the brush border of the intestine is damaged by the membrane-disruptive properties of tomatine, so increased uptake of macromolecules occurs. This damage to the epithelial barriers is dose-dependent. Tomatine is considered to be a fungitoxic compound, as it completely inhibits mycelial growth of the fungi C. orbiculare (MC100=2.0 mM), S. linicola (MC100=0.4 mM), and H. turcicum (MC100=0.13 mM). For the inhibition at a low pH, much more tomatine is required, so the compound is more effectively fungitoxic at a high pH, when the alkaloid is unprotonated. The unprotonated form of tomatine forms complexes with sterols such as cholesterol, which may cause disruption of cell membrane and changes in membrane permeability. Tomatine is effective against fungi at pH 8 but not at pH 4. A possible explanation for this is that the tomatine only in the deprotonated form binds to cholesterol to form the earlier mentioned complexes. Tomatine disrupts liposome membranes containing 3-β-hydroxy sterol, while liposomes without 3-β-hydroxy sterols are resistant to membrane disruption. Tomatine inhibits also the fungal types Ph. infestans and Py. aphanidermatum, which do not have any sterols in their membranes, so another mechanism of action must be present. Inhibition of acetylcholinesterase The other known action of the compound is the pH-dependent competitive inhibition of the enzyme acetylcholinesterase. The majority of synthetic pesticides used in agriculture work by inhibition of acetylcholinesterase is to kill insects. Metabolism Even now, little