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Prothoracicotropic (PTTH) and eclosion (EH) hormones were extracted from adult heads of Bombyx mori and PTTH was isolated by extensive chromatographic purification. A hormone (melanization and reddish coloration hormone, MRCH) inducing cuticular melanization and epidermal reddish coloration in the armyworm larvae of Leucania separata was also extracted from Bombyx adult heads. The chemical and biological properties of these hormones were investigated.

Several plant growth regulators were isolated from the culture broths of microorganisms, mainly phytopathogenic fungi, and their structures were determined. Helminthosporol ( 1 ) isolated from Helminthosporium sativum markedly promoted stem elongation of rice seedlings. From Exobasidium symplocijaponica was obtained L-s-phenyllactic acid ( 7 ) as a root growth promoter. Pestalotin ( 8 ) was isolated from Pestalotia cryptomeriaecola . The compound 8 enhanced the growth-stimulative effect of GA when applied in combination with the hormone. 2-Pyruvoylaminobenzamide ( 9 ) was isolated from Colletotrichum lagenarium as an antiauxin-like substance. From Cylindrocladium scoparium was obtained Cyl-2 as a growth inhibitor. Some Phytotoxins that cause disease in tobacco plants were isolated from Colletotrichum nicotianae : colletopyrone ( 11 ), colletotrichin ( 12 ). colletotrichin B ( l3 ) and colletotrichin C ( 14 ).

A simple and highly reproducible procedure for partial purification of prothoracicotropic hormone (PTTH, brain hormone) was established starting with 96,000 male adult Bombyx heads. The procedure consisted of twelve steps, i . e ., solvent extractions, precipitations and chromatographies. Approximately 28,500-fold purification of PTTH was accomplished with a 60% yield, and 6 ng of the most purified preparation could cause adult development in a debrained Samia pupa. The most purified PTTH was inactivated by trypsin and α-chymotrypsin, but not by aminopeptidases or carboxypeptidases. This suggests that both the N- and C-termini are blocked. By chemical treatments it was found that a tryptophan residue and disulfide bond(s) are essential for activity, whereas a sulfhydryl group is not. Gel filtration indicated the molecular weight of PTTH to be 4400.