A toxic component to mice was isolated from the viscera of cultivated carp (Cyprinus carpio) as white powder. Molecular formula was obtained to be $C_{27}H_{48}O_{8}S$ on the basis of the HRFABMS data. NMR spectra of the isolated compound were corresponded with those of $5{alpha}-cyprinol$ except the $C_{26}$ sulfated carbon. Therefore, it was identified as cyprinol sulfate ($5{alpha}-cholestane$ $3{alpha}$, $7{alpha}$, $12{alpha}$,26,27-pentol 26-sulfate). It showed toxicity to mice (2~3 mg/MU, i.p.), hemolytic activity ($500{mu}g/ml$) and prolyl endopeptidase inhibition ($IC_{50}$ > $200{mu}g/ml$), but, had no antibacterial, antifungal and cytotoxic activity to L1210 cells.