A ribonuclease, with a molecular mass of 23 kDa, and much higher activity toward poly(U) than poly(C) and only negligible activity toward poly(A) and poly(G), was isolated from the aqueous extract of Chinese ginseng (Panax ginseng) flowers. The ribonuclease was unadsorbed on diethylaminoethyl-cellulose and adsorbed on Affi-gel blue gel and carboxymethyl-cellulose. High activity of the ribonuclease was maintained at pH 6-7. On either side of this pH range, there was a precipitous drop in enzyme activity. The activity of the enzyme peaked at 50 degreesC and fell to about 20% of the maximal activity when the temperature was lowered to 20 degreesC or raised to 80 degreesC. The characteristics of this ribonuclease were different from those of ribonuclease previously purified from ginseng roots. (C) 2003 Published by Elsevier Inc.