1. Department of Biological Applications & Technologies, University of Ioannina, Ioannina GR-45110, Greece, Section of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-451 10, Greece, and Dipartimento di Chimica, Universita della Calabria, I-87037 Arcavacata di Rende, Italy