Chemistry of Gibherellins From Flowering Plants Alb 



MacMillan and Suter (6) have reported the isolation of Aj from 

 immature bean seed {Phaseolus multiflorns). The identification was 

 based on the identity of the infrared spectra of the free acid and 

 methyl ester of the isolated specimen and those of authentic Aj free 

 acid and ester and the identity of the melting points and mixed melt- 

 ing points of the methyl esters. West and Phinney (11) have reported 

 the isolation of two crystalline compounds with gibberellin-like bio- 

 logical properties, called bean factor I and bean factor II, from imma- 

 ture bean seed (Phaseolus vulgaris). These substances were incom- 

 pletely characterized. Sumiki during this conference reported the iso- 

 lation of Ai from water sprouts of mandarin orange (Citrus unshiu) 

 (9). These are the only reports to date of the isolation of gibberellins 

 from flowering plants in a sufficient state of purity to allow a useful 

 determination of physical and chemical properties. 



The purpose of this paper shall be to review the properties of 

 bean factor I and bean factor II and their implications for the struc- 

 tures of these materials. 



EXPERIMENTAL PROCEDURE 



Isolation 



The procedure employed for the isolation of bean factors I and 

 II has been described (11). The initial steps included extraction of 

 approximately 25 kg. of immature bean seed with acetone-water (1:1), 

 adsorption of the active substances onto charcoal from aqueous solu- 

 tion and re-elution with acetone (omitted in the second run) and ex- 

 traction of the active substances from aqueous buffer at pH 2 with 

 ethyl acetate. Further purification of this concentrate was achieved by 

 column chromatography on charcoal, column chromatography on 

 silicic acid, and countercurrent distribution. Crystallization was ef- 

 fected from ethyl acetate-petroleum ether solvent mixtures. The pro- 

 gress of purification was followed by bioassay on dwarf mutants of 

 maize. In one run approximately 2 mg. of bean factor I and 2 mg. of 

 bean factor II were recovered. In a second run approximately 1 mg. 

 of bean factor I and 5 mg. of bean factor II were obtained. 



Silicic acid chromatography has proved the most useful technique 

 for fractionating bean factor II from bean factor I. In a typical col- 

 umn 40 g. of prewashed and oven-dried silicic acid is dry-packed in 

 a column. The material to be chromatographed is adsorbed on a 

 small amount (2 g.) of silicic acid by evaporation from an organic 

 solvent and this mixture is packed on the top of the adsorbent col- 

 umn. The column is developed in succession with 400 ml. chloro- 

 form, 400 ml. of 20 per cent ethyl acetate in chloroform (by volume), 

 400 ml. of 40 per cent ethyl acetate in chloroform, 400 ml. of 60 per 



