Bioactive derivatives obtained from lecanoric acid, a constituent of the lichen Parmotrema tinctorum (Nyl.) Hale (Parmeliaceae)

With the aim of obtaining new compounds with potential antifungal activity, lecanoric acid, a chemical constituent of the lichen Parmotrema tinctorum and its derivatives prepared from structural modification were tested against the fungus Cladosporium sphaerospermum, by employing the bioautographic method. Activity of the derivatives ranged from 10to 1-μg concentrations. Results demonstrated this series of compounds to have potent fungitoxic activity. The search for new substances with antifungal activity has received increased attention over the past years, since few antifungal agents, and of limited action, are available for the treatment of systemic mycoses. Many compounds isolated from lichens have been effective in inhibiting growth of fungi and bacteria. In order to obtain compounds with potential activity against fungi, some derivatives of lecanoric acid (1), the main component of the lichen Parmotrema tinctorum, were prepared.