1960 Volume 29 Issue 5 Pages 411-414
1. Free protocatechuic acid found in the integument and exuvia at pupation period can not be detected in those at larval and imaginal moulting.
2. The acid content in the integument and exuvia just before and after pupation respectively is less than that of exuvia stored in laboratory.
By incubating the homogenates of the integument and fresh exuvia at pupation period at 37°C or hydrolizing them with 6N H2SO4 for several hours, protocatechuic acid can be extracted resulting in large quantity. From this, it may be infered that the majority of protocatechuic acid in the integument or fresh exuvia at the pupation period exist in a combined condition with unknown substance.
3. When newly laid pupal cuticle, soft and colourless, was immersed in tyrosine, catechol, 3, 4-dihydroxyphenyl acetic acid and protocatechuic acid, the cuticle manifested the most natural amber colour only in case of protocatechuic acid, while purplish black in tyrosine, brown in catechol and pale amber in 3, 4-dihydroxyphenyl acetic acid. From above mentioned results, the author supposes that at least protocatechuic acid is one of the phenols responsible for pigmentation in the pupal cuticle of the silkworm, Bombyx mori.
