Synergistic gastroprotective and antioxidative effects of natural olive oil and usnic acid isolated from Usnea longissima, a lichen species in Anatolia (Türkiye), in the indomethacin ulcer model created in rats

Usnea longissima, a medically important lichen growing up in forests in Anatolia (Turkey). In this study, the gastroprotective effect of usnic acid (UA) was investigated using an indomethacin (IND)-induced gastric ulcer model in rats. While 25, 50, 100 and 200 mg/kg UA doses were dissolved in 2 ml of olive oil (OO) and administered to rats, only OO was given to one group. In addition, lansoprazole (LAN) and ranitidine (RAN) and IND were dissolved in water and administered to rat groups. IND administration caused very high levels of damage to rat stomachs. On the other hand, when four doses of UA, OO, RAN and LAN were administered, it was determined that hyperemias in the stomach of rats was significantly reduced. After macroscopic analysis of gastric tissues, the activities of superoxide dismutase (SOD), catalase (CAT), myeloperoxidase (MPO) and nitric oxide synthase (iNOS and cNOS) enzymes as well as glutathione (GSH) and lipid peroxidation (LPO) levels were determined in these tissues. After IND application, it was detected increases in MPO, CAT and iNOS activities in gastric tissues and decreases in SOD, cNOS and GSH amounts. Four doses of UA, OO, RAN and LAN applications reversed the trend, bringing them closer to healthy levels.