Intermedin A, a New Labdane Diterpene Isolated from Alpinia intermedia, Prolonged the Survival Time of P-388D₁ Tumor-Bearing CDF₁ Mice

Eight ethanolic extracts of indigenous Taiwanese plants of the genus Alpinia were tested for tumor cytotoxicity against AGS, Hep G2, HeLa, KB, and HL-60 cells. Among the 50?% and 95?% EtOH extracts of eight Alpinia species, the cytotoxic effects of Alpinia intermedia leaves were the strongest. When the leaf extract of A. intermedia was partitioned using n-hexane and aqueous solvents, the n-hexane layer showed a greater cytotoxic effect and could prolong the survival time of P-388D₁ tumor-bearing CDF1 mice. Two new labdane diterpene derivatives, intermedin A (1) and intermedin B (2), and coronarin E (3) were isolated from the n-hexane layer of A. intermedia. Intermedin A induced apoptosis in HL-60 cells at 30 µg/mL and significantly prolonged the survival time of P-388D₁ tumor-bearing CDF₁ mice by 48.7?% at 20 mg/kg of body weight. We suggest that intermedin A is a major compound of A. intermedia and has a cytotoxic effect on HL-60 and P-388D₁ cells.