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Evidence based on theoretical calculations and photophysical experiments is presented to show that, contrary to general belief, the photostability of 2-(2'-hydroxy-5,-methylphenyl)benzotriazole (Tinuvin P) cannot be explained as being due to an excited-state intramolecular proton transfer (ESIPT) through the intramolecular hydrogen bond (IMHB). Support for this conclusion comes from a related study on several members of a new family of photostable compounds, namely the

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Three new diterpenoids, a neoclerodane and two labdane derivatives, have been isolated from an acetone extract of Plectranthus ornatus. The structures of these compounds (plectrornatins A-C, 1-3, respectively) were established mainly by spectroscopic means, particularly by 1D and 2D NMR studies and, in the case of the neoclerodane 1, by an X-ray diffraction analysis. Compounds 1 and 3 showed moderate antimicrobial activity against five Candida species and selected Gram negative and Gram positive bacteria strains.