In Ixeris Sonchifolia H., which is an edible and medicinal plant in Korea chlorgenic acid was identified by P.P.C. and T.L.C. Sixteen total amino acids (Asp, Thr, Ser, Glu, Pro, Gly, Ala, Val, Met, Ile, Leu, Tyr, Phe, Lys, His, Arg) including seven essential amino acids except tryptophan were identified in Ixeris Sonchifolia H. Of these sixteen amino acids, especially proline was contained in the highest amount. The extract of the plant showed an antineoplastic action on Ehrlich carcinoma.