In the previous communication from these laboratories, it has been reported that the basic fraction of Dendrobium nobile consisted of four crystalline alkaloids at least, among which dendrobine and nobilonine were fully investigated and their structures were clarified to be I and II respectively. The present communication is concerned with the third alkaloid, for which the name of dendroxine is proposed. Dendroxine, m.p. 114 ~ 115°, (α)D -30.1 (in EtOH), pKa'=4.5 (in 50% EtOH) possesses an empirical formula of C17H25O8N (Anal. Calcd.: C, 70.07; H, 8.65; N, 4.81. Found: C. 70.22; H. 8.67; N. 4.81. Molecular weight: 291 (mass spectrometric determination)) and the presence of γ-lactone (1778 cm-1) and absence of hydroxyl group are deduced from its infrared absorption spectrum in potassium bromide. Nuclear magnetic resonance spectrum (NMR) indicates the presence of two secondary methyl groups (9.05 τ; 6H, q, J=6 c/s), and one tertiary methyl group (8.80 τ; 3H, s) but the proton signal due to an N-methyl group can not be observed, contrary to those of dendrobine and nobilonine. The signal due to the methine proton adjacent to the lactone oxygen appears at 5.90 τ as a doublet (J=3 c/s), suggesting the partial structure (i) in dendroxine. 76 mg of pure compound is obtained from 82 kg of fresh bulbs (stems) of Dendrobium nobile.