Indole-3-acetaldehyde in Plant Extracts 



47 



Paper Chromatography 



All the chromatography was carried out on Whatman No. 1 filter 

 paper. Except for a few control experiments, the plant extracts and 

 synthetic samples were chromatographed in hexane (27, 28) . The de- 

 scending technique was used. The solvent (7z-hexane, Merck) was 

 shaken with water before use, but no water was placed in the upper 

 trough. The atmosphere in the tank was kept saturated with water 

 vapor by means of a sheet of filter paper dipping into a separate 

 trough containing water. 



Nitsch and Nitsch (27, 28) emphasize that the water conditions 

 during the experiment have a pronounced influence on the Rf values 

 of IAN and ethyl indole-3-acetate (lAEt) . Our Rf values for IAN and 

 lAAld were low, but reproducible. They were 0.10 and 0.055, respec- 

 tively. Rf values for lAEt were variable (0.38 to 0.57) , and more streak- 

 ing occurred behind the spot. In order to get good separation of lAAld 

 and IAN, the chromatogram was run for 18 hrs. or more. Under these 

 conditions, of course, the front would run off the paper and for a 

 direct determination of Rf values, chromatograms had to be run for a 

 shorter time, e.g., Si/o hrs. IAN and lAAlcl were used as reference 

 markers in the establishment of Rf values for other compounds in the 

 18 hr. runs. 



RESULTS 



Synthetic compounds. CJiromatography. A list of Rf values in water- 

 saturated n-hexane and color reactions with DMCA given by lAA and 

 a few neutral indole derivatives is given in Table 1. It will be seen that 

 the two compounds with which we were most directly concerned, IAN 

 and lAAld, can be distinguished without difficulty. These two auxins 

 became well separated when applied in mixture to the same starting 

 point. 



Table 1. Rf values in water-saturated 7z-hexane (Merck) and color reactions 

 with dimethylaminocinnamaldehyde (DMCA) given by lAA and some neutral indole 

 derivatives. 



