Abstract: A new alkaloid, mucronatine, C₁₈H₂₅NO₆, m.p. 179-181℃, has been isolated from the seeds of Crotalaria mucronata, which was collected from the suburb of Canton in Southern China. The following salts have been prepared: (1) tartrate m.p. 212-213℃; (2) hydrochloride m.p. 245℃ (decomp); (3) picrate m.p. 233-235℃; and (4) chloroaurate m.p. 120-123℃. On hydrolysis with baryta water it gave a crystalline necine, C₈H₁₃NO₂, m.p. 164℃, and a necic acid C₁₀H₁₆O₆, m.p. 181-184℃, respectively. The acid seems to be identical with retronecic acid from its physical and chemical properties. The partial structure of mucronatine may be expressed as formula (Ⅱ).