“…Some natural products act like non-selective PDE inhibitors as the methylxanthines caffeine and theophylline, but others show similar effects to PDE-5 inhibitors, for example: flavonoids and derivatives (quercetin from Allium cepa, pyrano-isoflavones from Eriosema kraussianum -Kraussianone 1 and 2); alkaloids (Neferin from Nelumbo nucifera, Berberine from Berberis aristata, Papaverine from Papaver somniferum -used in association with Prostaglandin-E1 to injections intracavernosal), saponins (Steroidal saponins from Allium tuberosum), coumarins (Osthole from Angelica pubescens) and terpenes (Forskolin from Coleus forskohlii) (Drewes et al, 2003;Guohua et al, 2009;Rahimi et al, 2009;Sumalatha et al, 2010;Zanolari, 2003). The success of PDE-5 inhibitors, particularly of Viagra, the first inhibitor that has been marketed, the aging of the population and the quest for improved quality of life led to the search for new drugs with fewer side effects.…”