Poster: Secondary metabolism

Abs # 249: Structure-related fungitoxicity of capsidiol phytoalexin.

Presenter:	Garcia-Pineda, Ernesto , egpineda@zeus.umich.mx
Authors	Garcia-Pineda, Ernesto  (A)   Soriano-Bello, Eva L.  (A)   Castro-Mercado, Elda  (A)   Arreola-Cortés, Araceli  (A)
Affiliations:	(A): U.M.S.N.H., Instituto de Investigaciones Químico Biológicas

Phytoalexins have been shown to inhibit growth of a variety of organisms such as fungi, bacteria, and nematodes. Their synthesis can be stimulated by pathogens and a variety of biotic and abiotic elicitors. Phytoalexins and their derivatives may have potential application as pesticides (Paxton, 1991). This concept, however, is not practical due to the plant pathogenic fungi have evolved mechanisms to detoxify phytoalexins. It might be possible to biologically engineer the phytoalexins to produce a different phytoalexins which the fungal pathogens cannot detoxify (Laks and Pruner, 1989). Information on the phytoalexins would be valuable in developing this type of approach. To analyze the structure/activity relation of capsidiol phytoalexin, which is the main phytoalexin in Capsicum annuum, capsidiol production was stimulated in pepper fruits by cellulase. After purification by TLC, capsidiol was acetylated in the presence of pyridine to modify the OH groups, and analyzed by gas chromatography/mass spectrometry. The antifungal activity of capsidiol and its derivative was tested in vitro on Phytophthora capsici, a pepper pathogen . The preliminary bioassay indicated that capsidiol acetylated exhibited a decrease in fungicidal activity against Phytophthora capsici. This could indicate that the OH group is indispensable to the capsidiol activity. In addition, its effect over zoospores germination and bacterial growth are being characterized. Paxton JD (1991). ACS Symposium Series 449; American Chemistry Society: Washington, DC, pp 198-207; Laks PE, Pruner MS (1989). Phytochemistry 28: 87-91.