Chemical constituents from the leaves of Pseuderanthemum tunicatum (Afzel.) Milne-Redhead (Acanthaceae)

Phytochemical study of the ethanol extract of the leaves of Pseuderanthemum tunicatum afforded eleven known compounds including madagascin (1), harunganol B (2), eicosanoic acid (3), dotriacontanoic acid (4), friedelin (5), lupeol (6), β-sitosterol (7), stigmasterol (8), β-sitosterol 3-O-β-d-glucopyranoside (9), stigmasterol 3-O-β-d-glucopyranoside (10) and apigenin 7-O-β-d-glucopyranoside (11). Acetylation of compound 1 afforded madagascin diacetate (1a), described here for the first time. The structures were established by interpretation of their spectral data, including IR, UV, MS, 1D- and 2D- NMR (1H, 13C, DEPT 135, 1H-1H COSY, HMQC, HMBC and NOESY), as well as by comparison with literature data. In the present study all the compounds are isolated for the first time from the species P. tunicatum. Compounds 1 and 2 have never been reported from the Acanthaceae family. Compounds 4 and 6-11 have been previously isolated from the genus Pseuderanthemum, and compounds 3 and 5 from the family Acanthaceae. The chemotaxonomic significance of the isolated compounds is discussed.