Plants belonging to the genus Nepeta have long been employed in traditional medicine for treating skin ailments and snake envenomation because of their antiseptic and astringent properties. Despite the recognized phytochemical diversity of this genus, Nepeta racemosa has not been thoroughly investigated. The present study aimed to characterize the phytochemical constituents, essential oil profile, and antioxidant potential of this species. Dried aerial parts of N. racemosa were extracted sequentially using n-hexane, chloroform, and methanol through maceration. The methanolic extract was fractionated by C18 solid-phase extraction using a graded methanol–water system. Selected fractions were further purified by preparative reversed-phase high-performance liquid chromatography, resulting in the isolation of three secondary metabolites. The volatile components of the essential oil were identified by gas chromatography–mass spectrometry. Antioxidant capacity was determined using the DPPH radical scavenging assay, while total phenolic and flavonoid contents were quantified using Folin–Ciocalteu and aluminum chloride colorimetric methods, respectively. Chemical investigation of the 20% and 40% solid-phase extraction fractions led to the identification of an iridoid compound, 8,9-epi-7-deoxy-loganic acid, along with two phenylethanoid glycosides, forsythoside B and verbascoside. Analysis of the essential oil revealed 4aα,7α,7aα-nepetalactone (31.70%) as the predominant constituent, followed by germacrene D (7.39%) and n-hexadecanoic acid (6.47%). Among the tested samples, the methanolic extract exhibited marked antioxidant activity and the highest levels of phenolic and flavonoid compounds (IC₅₀ = 0.09 ± 0.01 mg/mL; 1581.80 ± 10.28 mg/100 g; 33.01 ± 0.02 mg/100 g). The 40% solid-phase extraction fraction also demonstrated strong radical scavenging ability, accompanied by substantial phenolic and flavonoid contents (IC₅₀ = 0.01 ± 0.00 mg/mL; 659.20 ± 40.32 mg/100 g; 22.50 ± 0.37 mg/100 g). This study indicates that phenylethanoid glycosides are key contributors to the antioxidant properties of Nepeta racemosa, highlighting this species as a valuable source of bioactive phenolic compounds.
