Phytochemical Analysis and In Vitro Biological Activities of Three Endemic Origanum species

Origanum species (oregano), which have been used as spices and medicines since ancient times and are one of the important riches of our country, are also known as important species in terms of the bioactive compounds they contain. In this study, phytochemical contents and biological activities of methanol extracts (OMİN, OSAM and OSOM) obtained from the aerial parts of three endemic Origanum species, Origanum minutiflorum, O. saccatum and O. solymicum, were comparatively analyzed. Extracts were obtained by maceration method. Antioxidant, anti-inflammatory and antidiabetic activities were evaluated using DPPH/ABTS radical, 5-lipoxygenase and α- glucosidase inhibition methods, respectively. Total phenol, flavonoid and triterpene contents were calculated by Folin-Ciocalteu, AlCl3 and Acetic acid/Vanillin/perchloric acid methods, respectively. Phenolic compounds of the active extract were analyzed by HPLC. OSAM with IC50 values of 13.51 µg/mL and 81.23 µg/mL exhibited the strongest antioxidant activity against DPPH and ABTS radicals. OSAM with IC50 value of 84.11 µg/mL and OSOM with IC50 value of 102.00 µg/mL showed the best inhibitory activity against α-glucosidase and 5-lipoxygenase enzymes, respectively. Total phenol and flavonoid content was highest in OSAM (132.30 and 60.32 mg/g) while total triterpene content was highest in OMIN (177.39 mg/g). In the HPLC analysis of the most active OSAM, rosmarinic acid as the major compound was detected in very high amounts (211.061 mg/g extract). These results show that OSAM has a strong antioxidant and antidiabetic activity and that other phenolic acids and flavonoids, especially rosmarinic acid, may be responsible for this activity. However, in vivo studies are needed to be sure of the activities and bioactivity-directed fractionation method is needed to reveal the compounds responsible for the activity.