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The UVA irradiation of 9-fluoro-2,3-dihydro-10-4'-methyl-1' -piperazinyl-7-oxo-7H-pyrido[1,2,3-de]-1,4-benzo-thiazine-6-carboxylic acid, rufloxacin, a fluoroquinolone antibacterial that shows photosensitizing properties toward biological substrates, leads to formation of two main steady photoproducts characterized by a decarboxylation process and an opening of the piperazinyl ring, respectively. The deprotonation of the 10-piperazinyl group and the dissociation of the 6-carboxyl group of rufloxacin are strictly pH dependent. The photosensitizing activity was tested toward membranes as biological targets. Red blood cell hemolysis and lipid peroxidation were considered as markers of photosensitization. Ultraviolet A-induced damage is strongly influenced by the presence of oxygen, it is triggered by transient species, such as singlet oxygen and free radicals, photogenerated via rufloxacin irradiation, whereas no drug photoproduct is involved in the photosensitization process.

The stilbenoids E-resveratrol (E-3,5,4Ј-trihydroxystilbene, 1), E-3,5,4Ј-trimethoxystilbene (2), E-3,4,4Ј-trimethoxystilbene (3) and E-3,4Ј-dimethoxy-5-hydroxystilbene (4) were converted by photoisomerization to their corresponding Z-isomers 5Ð8. Compounds 1Ð8 were subjected to antiproliferative activity bioassays towards a set of four different human cancer cell lines, namely DU-145 (androgen not responsive human prostate tumor), LNCaP (androgen responsive human prostate tumor), M-14 (human melanoma) and KB (human mouth epidermoid carcinoma). The methylated analogues of 1 are more active than the natural lead in the majority of bioassays. The most active compound was Z-3,5,4Ј-trimethoxystilbene (6), which showed against DU-145 and LNCaP cells GI 50 values close to those of the anticancer drug vinorelbine; 6 resulted more active than its E-isomer 2 towards DU-145, LNCaP and especially KB cell lines. A number of methylated Z-isomers displayed a higher activity than their E-isomers, but E-resveratrol (1) was more active than Z-resveratrol (5) towards all the tested cell lines.

The photochemistry of the anticancer drug flutamide (FM), 2-methyl-N-[4-nitro-3-(trifluoromethyl)phenyl]propanamide, in homogeneous media and in the beta-cyclodextrin (beta-CD) cavity has been investigated. The photoreactivity of the free molecule has been rationalized on the basis of an intramolecular nitro to nitrite rearrangement followed by cleavage of the nitrite intermediate. The twisted geometry of the nitro group with respect to the aromatic plane plays a key role in triggering such a photoprocess. Incorporation of FM in the beta-CD cavity leads to dramatic effects on both the efficiency and the nature of the photochemical deactivation pathways of the guest molecule. A 20-fold increase in the FM photodecomposition quantum yield and the formation of photoproducts originated by both reduction of the nitro group and cleavage of the amide bond were observed in the presence of the macrocycle. Such a behavior cannot be attributed exclusively to the micropolarity of beta-CD and/or to its role as a reactant. The induced circular dichroism spectra and the nature of the photoproducts formed in these experimental conditions provide indications that the photoreactivity in the beta-CD microenvironment could likely be mediated by structural changes of FM upon complexation.