Simple Spectrophotometric Analysis of Flavonoids from the Cocoon Shell of the Silkworm, Bombyx mori

Abstract

The cocoon shells of several silkworm races contain flavonoids. We recently found that cocoon shells of Ryokuken races such as Daizo contain specific flavonoids that are almost non-existent in cocoon shells of Sasamayu races such as Pure Mysore. Usually, LC-MS systems are used to analyze flavonoids in cocoon shells. However, these systems require a great deal of time and effort to operate and maintain. Here, we confirmed that absorbance at a wavelength of 365 nm of aqueous methanolic extracts of the cocoons was well correlated with the total flavonoid content of the cocoons. The absorbance ratio (A420 nm: A365 nm) of the extracts was correlated with the percentage of Ryokuken-specific flavonoids in the cocoons. We propose a simple analytical method using a UV-VIS photospectrometer to roughly estimate the amount and composition of cocoon flavonoids. This may help in the genetic study and breeding of Ryokuken and Sasamayu races.