Profundización en el estudio de la actividad antioxidante de los polifenoles de Lethariella canariensis (ACH): Krong

Abstract

Lichen species typically have a characteristic profile of secondary metabolites. One of the most abundant sources of these compounds is the lichen Lethariella canariensis (Ach.) Krog, which is widely distributed on five islands of the Canarian Archipelago. Dense populations of this species grow frequently on volcanic land. Previous studies have demonstrated that lichen substances have more than one phenolic hydroxyl group attached to one or more benzene rings, thus qualifying as polyphenols. The aim of the present study was to re-characterise the suite of secondary metabolites of L. canariensis with modern analytical techniques and to estimate their antioxidant activity. The compounds were identified based on their IR, MS and 1H-NMR spectra as well as retention factors of their TLC analysis. In addition to the previously described secondary metabolites (atranorin and chloroatranorin) of L. canariensis, further ten were identified in its thalli: atranol, chloroatranol, hematommic acid, chlorohematommic acid, methyl hematommate, methyl chlorohematommate, ethyl hematommate, ethyl chlorohematommate, methyl β-orsellinate, and (+)-usnic acid. These polyphenols have been restudied with intention to find compounds protecting against oxidative stress and free radical-induced damage. Protection against lipid peroxidation was investigated using brain homogenates. The mixture Letharal decreased H2O2/Fe+2 induced lipid peroxidation in a concentration-dependent manner. The L. canariensis polyphenols exhibited 180-1339 fold less radical scavenging activity than reference substance α-(+)-tocopherol in DPPH• model expressed by IC50 values.