Phytopathological Chemistry of Black-rotted Sweet Potato

Part 4. Isolation and Identification of Polyphenols from the Injured Sweet Potato (I)

Abstract

As reported in the previous paper, polyphenols are accumulated in black-rotted sweet potato. For the clarification of their pathological roles, the authors made an attempt to isolate the polyphenols from the injured potato, chiefly according to the method which was introduced by G. RUDKIN and J. NELSON.
Eighteen kg. of sweet potatos were cut into slices of 1 cm. thick. Each slice was inoculated with spore suspension of Ceratostomella fimbriata, left during 5_??_6 days at 25°, and steamed to destroy its ouidase. Then 7kg. of the sound parts adjacent to the injured were extracted, with boiling acetone. After treating this extract with Pb-acetate, ethyl acetate, 13g. of the phenolic fraction were obtained in the form of crude yellow powder. From this powder, two phenolic components, A and B, were separated by the counter current distribution method (C. RUDKIN and J. NELSON, ) yielding 4.5g. and 2.8 g. respectively. After carrying out this procedure again, and the fractional precipitation with ethyl acetate and chloroform, an acid was isolated in the shape of needles, melting at 205_??_6° from B. Its pentaacetyl derivative, mp 178°, was prepared, The results of the analyses and the mixed melting pt. with purified chlorogenic acid, prepared from coffee beans, showed that this substance must be the chlorogenic acid. Another component A will be reported in the later paper.