Abstract
In the 3rd and 4th reports of this series it was described that the yellow fluorescent pigments in the green cocoon of silkworm var. Daizo with the genotype Gc/Gc were flavonoids or flavonoid-like pigments and biosynthesized in the alimentary canal from some precursores in mulberry leaves. Furthermore, it has been known that flavonoid pigments such as quercetin and its glycosides, isoquercitrin and rutin, are present in the leaves of usual mulberry tree and morin is present in the heartwood of Morus tinctria, a family of mulberry tree, and protocatechuic acid and β-resorcylic acid are easily derived from quercetin and morin by alkali-fusion reaction respectively.
In this report, addition of these flavonoid or flavonoid-like pigments to the artificial diet, in expectation of produce of colored cocoon by larvae fed on the diets, was examined. When the larvae having the genotype Gc/Gc were fed on the artificial diet without any source of these flavonoids or flavonoid-like pigments, they produced non coloured cocoon.
Single addition of quercetin or its glycosides to the diet came up to our expectation showing that same yellow fluorescent pigments were produced by larvae fed on these artificial diets as by larvae reared on mulberry leaves. The larvae fed on the diet containing a flavonoid, morin, produced golden yellow cocoon but its pigments were distinct from those of the ordinary cocoon. Protocatechuic acid and resorcylic acid were not effective to the formation of the pigments. It was concluded that the precursor of yellow fluorescent pigments in the green cocoon should be quercetin and its glycosides, isoquercitrin or rutin in mulberry leaves.
