Sesquiterpene lactones from Mikania micrantha and Mikania cordifolia and their cytotoxic and anti-inflammatory evaluation.

The guaianolide 8-epi-mikanokryptin (1) and the melampolide 11Hβ-11,13-dihydromicrantholide (2) along with known sesquiterpene lactones (3-13) and other constituents were isolated from the aerial parts of different populations of Mikania micrantha and Mikania cordifolia collected in several states of Mexico. The relative and absolute configurations of 1 were determined by X-ray diffraction and CD analysis, respectively. Considering the (1)H and (13)C NMR chemical shift similarities and the H-H coupling constant values, a [(1)D(14), (15)D5] conformation was established for micrantholides (2, 8-13).

Dependence of DNA-protein cross-linking via guanine oxidation upon local DNA sequence as studied by restriction endonuclease inhibition.

Oxidative damage plays a causative role in many diseases, and DNA-protein cross-linking is one important consequence of such damage. It is known that GG and GGG sites are particularly prone to one-electron oxidation, and here we examined how the local DNA sequence influences the formation of DNA-protein cross-links induced by guanine oxidation. Oxidative DNA-protein cross-linking was induced between DNA and histone protein via the flash quench technique, a photochemical method that selectively oxidizes the guanine base in double-stranded DNA.