Several alkaloids of unknown structures were isolated from the root bark of Tiliacora racemosa Colebr (Menispermaceae). Previous studies assigned a common gross structure (I) (dibenzo-ß-dioxin containing bisbenzylisoquinoline moiety with a diphenyl unit) to four alkaloids (tiliacorine, tiliacorinine, nortiliacorinine A and B), but the exact locations of the phenolic OH and methoxy group on the diphenyl fragment remained unknown. Recent pharmacological screening on the methiodide of the crude alkaloid from the leaves revealed a strong hypotensive effect, prompting a detailed investigation of the crude extract. This resulted in the isolation of a new alkaloid, tiliamosine, C₃₉H₃₆N₂O₈ (II) as its N-acetate C₄₁H₃₈N₂O₉ (IIa), and N-acetylnortiliacorinine A (C₃₉H₃₆N₂O₇, Ic) as major components. Mass fragmentation patterns, spectroscopic (IR, NMR) and chemical data indicated tiliamosine shares a common gross skeletal structure with tiliacorine-type alkaloids. Through extensive spin decoupling and Nuclear Overhauser Effect (NOE) experiments, spectral analysis showed tiliamosine differs from N-acetylnortiliacorinine A (Ic) by having one less aromatic proton, one more methoxy group (three instead of two), with the additional methoxy group located at C-20. Thus, tiliamosine is the first dibenzo-p-dioxin containing bisbenzylisoquinoline alkaloid with a benzocyclic ring possessing four ether oxygen atoms, representing a new type of bisbenzylisoquinoline alkaloid.