Chemical composition, antioxidant, and enzyme inhibition activities of Crithmum maritimum essential oils: the first chemo-biological study for species grown in North Africa

Crithmum maritimum (sea fennel), is a halophytic plant species found globally in coastal environments. This study is the first investigation into the chemical composition and biological activities of C. maritimum growing wildly in Jebel Akhdar, Libya. Gas Chromatography-Mass Spectrometry (GC-MS) analysis was utilized to identify and profile the plant's volatile components; it resulted in the identification of twenty-four components, representing 99.17% of the total peaks in the GC-MS chromatogram. The analysis revealed that thymyl methyl ether, γ-terpinene, and ledene oxide, were the major volatile constituents of the plant at relative percentage levels of 56.86, 16.17, and 4.32%, respectively. The analysis also indicated substantial variations in the volatile composition of C. maritimum Libyan species compared to those from various geographic regions. The plant's volatile oil quality was evaluated by investigating its in vitro antioxidant activity and the oil's ability to inhibit acetylcholinesterase (AChE) and tyrosinase enzymes. The oil markedly scavenged the free radicals and reduced the ferric ions in the DPPH and FRAP assays at levels of 34.30 ± 0.10 and 38.90 ± 0.51 Trolox equivalents, respectively. The plant's volatile oil has substantially reduced the AChE at the IC₅₀ value of 34.43 ± 0.25 compared to its effect against tyrosinase (IC₅₀ 12.449 ± 0.68). The in silico approach was used to highlight the mechanisms underlying the enzyme inhibitory effect of the plant volatile oil. The stigmastene and γ-santonin demonstrate stronger binding affinity towards AChE and tyrosinase compared to the co-crystalized controls, donepezil and tropolone. The study provides significant information for the environmental changes effect on the volatile constituents of C. maritimum and highlights the plant's importance within the scope of its antioxidant and enzyme inhibition activities.