Chemical characterization of alpha hormones of Phytophthora parasitica

A method for the large scale hormone alpha 1 and alpha 2 extraction from ag ar cultures of A1 and A2 mating types of Phytophthora pamsitica has been de veloped. Using a total of 240 L of organic solvents to extract 40 L of the agar medium, sufficient amounts of alpha hormones were obtained to permit c haracterization of their physical and chemical properties. Activities of bo th hormones were in the neutral fractions in acid-base partition. These hor mones were not precipitated by cold acetone or digitonin, nor were their ac tivities destroyed by saponification. Fractionation on an aminopropyl colum n showed that both hormones were neutral lipids with polarity similar to th at of monoglycerides and that alpha 2 had a polarity greater than that of a lpha 1. Both hormones were stable at 200 degrees C under nitrogen, and alph a 1 was more volatile than alpha 2. After acetylation, the hormonal activit y of alpha 1 was retained, while that of alpha 2 was greatly reduced. Base hydrolysis of the acetylated alpha 2 led to the restoration of its hormonal activity. Using semi-preparative gas chromatography, alpha 1 activity was eluted between 230 and 278 degrees C while alpha 2 could not be eluted unde r the same conditions. Results from this study suggest that cc hormones are not phospholipids, glycolipids, glycerides, or steroids, but that they are probably neutral lipids with hydroxyl functional group(s). Structural eluc idation of alpha 1 and alpha 2, however, would require an even greater scal e of operation than that provided by the present experiment.