Origanum boissieri Ietsw., O. saccatum P.H.Davis, O. solymicum P.H.Davis and O. ayliniae Dirmenci & T.Yazici belonging to sect. Amaracus (Gled.) Vogel, O. sipyleum L. and O. hypericifolium O.Schwarz & P.H.Davis belonging to sect. Anatolicon Ietsw. were analyzed for their chemical composition of essential oil and phenolic components. The essential oil compositions were analysed by using GC-MS and GC-FID. The phenolic contents of the chloroform, acetone, and methanol extracts were analyzed using LC-MS/MS. Antioxidant activities of the extracts were investigated by using three methods; DPPH free radical scavenging activity, beta-carotene linoleic acid assays and CUPRAC assays. The essential oil compositions of the section Amaracus were found to be as carvacrol type (O. ayliniae, O. boissieri) and p-cymene type (O. saccatum, O. solymicum). In the section of Anatolicon, while O. sipyleum was found as gamma-terpinene type, O. hypericifolium was carvacrol type. In the extracts, the most abundant components were determined as flavonoids, coumaric acids and derivatives. Especially rosmarinic acid and penduletin were detected in high amounts. Among the studied species, extracts of O. ayliniae showed quite good activity for all methods. The extracts from all species showed remarkable antioxidant activity. Inhibition capability of the extracts against acetyl and butyrylcholinesterase enzymes (AChE and BChE) were determined. The extracts were found as inactive against AChE. The moderate inhibition capacity observed against BChE. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of King Saud University.