• Applied Biological Chemistry
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• v.10
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• pp.47-61
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• 1968

Sweetpotato infected by Soft-rot, Rhizopus nigricans, has been investigated for its biochemical changes. The results of the present experiment are summarized as follows: 1. From the Soft-rotted tuber, nineteen Ehrlich's positive substances and three fluorescent compounds which had not been found in a healthy tuber were detected with thin layer chromatography. 2, Ipomeamarone and umbelliferone, each of which are predominating substances among the Ehrlich's positive and fluorescent compounds, were isolated by silica gel column chromatography and studied for their identities. 3. Time course biosynthesis of the metabolites was studied and discussed for their possible biosynthetic pathways. 4. Among the metabolites, ipomeamarone and ipomeamarone-like substances have enzyme: inhibitive action against ${\alpha}$-amylase and probably other enzymes; the inhibition type was determined as the uncompetitive one. 5. Ipomeamarone obtained from soft-rotted sweetpotato was proved to have an uncoupling action as 2, 4-dinitrophenol.

• Applied Biological Chemistry
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• v.10
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• pp.63-68
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• 1968

The effects of $^{60}Co-{\gamma}$ radiation on the change of composition and susceptibility to soft rot during the storage of sweetpototoes and the radioresistance of spores of the soft rot fungus were investigated and the following results were obtained. 1) Gamma-irradiation of sweetpotatoes caused the increase in water-soluble sugar content and the decrease in ascorbic acid content during the storage. 2) The rate of oxygen uptake in sweetpotato slices becomes higher as the dose increases. But the oxygen uptake in slices irradiated with higher doses decreases along with the color change as the time passes. 3) Irradiation with high doses (above $2.5{\times}10^5$ rad) brought about the increased susceptibility to soft rot decay as the chilling injury did in the storage of sweetpotatoes. 4) Average lethal dose for the spores of Rhizopus nigricans was $3.0{\times}10^5$ rad and the complete death required the level of $1.25{\times}10^6$ rad.