The author had already studied the natural pigments of Japanese green cocoon (var. Seihaku) and isolated from it a new pigment, "Bombycin", which showed flavonol-glucoside reaction, and contained one atom of nitrogen.The author tried too isolate bombycin from mulberry leaves but could never find it and, in place of it, isolated fine crystallizable compound, which was identified as isoquercitrin, which is a quercetin monoglucoside (3-glucoside).Isoquercitrin was. already isolated from brown-husked maize by Sando and Bartlett and from cotton flower by Perkin, but the author was the first to isolate it from mulberry leaves.Preparation of Isoq ercitrhn.The air dried ground powder of mulberry leaves was extracted with boil ing 80% alcohol three times and the extract was concentrated, which was shaken with ether and ether soluble substances were rejected. To the water soluble fraction was added neutral lead acetate and the yellow, precipitate formed was decomposed by hydrogen sulphide. Seeing that both the lead sulphide and its filtrate contained considerable amount of flavonol glucoside, it was removed by repeated shakings with ethyl acetate. The ethyl_acetate extracts were then, evaporated and the residue was dissolved in adequate amount of water and then shaken with toluene and left still in a ice box
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