1. Institute of Botany, University of Urbino, via Bramante 28, 61029 Urbino, Italy
2. Department of Chemistry, Laboratory of Organic Chemistry, University of Perugia, via Elce di Sotto 8, 6123 Perugia, Italy
3. Dip. Farmaco-Chimico-Tossicologico, University of Sassari, Via Muroni 23, I-07100 Sassari, Italy