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The chemical investigation of the methanolic extract of the root bark of Waltheria douradinha (Sterculiaceae) afforded an unusual quinolinone alkaloid named waltherione-A (1). Its structure was determined mainly by NMR spectroscopic methods. The antibacterial activity of waltherione-A (1) and the corresponding O-methylated derivative (2) was tested against three gram-negative and three gram-positive bacteria, with only (2) having moderate activity.

The cyclopeptide alkaloid, named condaline-A, was isolated from the root bark of Condalia buxifolia Reissek (Rhamnaceae), along with the known compounds adouetine-Y', scutianine-B, and scutianine-C. Their structures were determined by spectroscopic analyses, with their antibacterial activities being evaluated by use of a direct bioautography method.

A new quinoline alkaloid named helietidine ( 1), and seven known compounds ( 2 - 8) have been isolated from the stem barks of Helietta longifoliata. The structures of the new and the known compounds were established on the basis of spectral evidence, especially by 2D NMR ( 1H- 1H COSY, NOESY, HMQC, HMBC). In addition, the volatile constituents of H. longifoliata leaves were analysed by gas chromatography-mass spectrometry (GC-MS). Twenty-five constituents were identified representing ca. of 96 % of the oil, and limonene (17.50 %), germacrene D (16.60 %), elemol (11.81 %), bicyclogermacrene (11.67 %), guaiol (11.53), and epi-alpha-bisabolol (7.24 %) were the most abundant components. The oil was bioactive against some Gram-positive and Gram-negative bacteria, as revealed by bioautography.