**1. Introduction**

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, particularly a ffecting the cerebral cortex and hippocampus, leading to memory impairment. AD pathological hallmarks include extracellular accumulation of insoluble forms of amyloid-β, aggregation of the microtubule protein tau in neurofibrillary tangles in neurons, as well as the reduction in levels of acetylcholine [1,2].

Among various descriptive hypotheses regarding the cause of AD, the cholinergic hypothesis was the first proposed to explain AD based on the findings that a loss of cholinergic activity is commonly observed in the brains of AD patients [1]. In addition, this theory implied utilizing acetylcholinesterase inhibitors (AChEIs), which reversed memory deficits in AD patients. AChEIs could diminish memory impairment in AD patients by inhibiting the degradation of acetylcholine [3]. Currently, for the treatment of mild to moderate AD, three AChEIs are used: donepezil, rivastigmine, and galantamine [4]. Moreover, it has been reported that the daily living ability of AD patients subjected to rivastigmine and

galantamine medications is better than those treated with donepezil [5]. AD is additionally associated with neuropsychiatric symptoms such as depression, anxiety, and apathy [6]. Oxidative stress is involved in age-related diseases and the pathological processes of neurodegenerative diseases, including AD [7].

Presently, there is no remedy for dementia-related a fflictions, and existing medicines do not give satisfactory enhancements. Moreover, there are di fferent side e ffects related to existing treatment. Herbal-based compounds could be a grea<sup>t</sup> source of anti-AD agents [8].

Although numerous studies have been performed to elucidate the e ffects of *Rosmarinus o*ffi*cinalis* extract on cognitive function in rodents [9–11], there is no such study conducted in zebrafish. Zebrafish exhibit complex cognition comparable to that seen in mammals [12,13], and there are behavioral tasks protocols based on rodent protocols such as active or passive avoidance test [14], Y-maze test [15], and T-maze test [16] for zebrafish. In zebrafish, scopolamine, a muscarinic acetylcholine receptor blocker, has been characterized to induce amnestic e ffects and is used in combination with nootropic and cognitive-enhancing drugs to study memory processes [17].

Supporting data demonstrate di fferent biological e ffects of *Rosmarinus o*ffi*cinalis* L. Nematolahi et al. [18] demonstrated that *Rosmarinus o*ffi*cinalis* reduced memory-deficits, anxiety, and depression, and improved sleep quality in university students. Naderali et al. [9] reported that *Rosmarinus o*ffi*cinalis* extract improved memory deficits and mitigated neuronal degeneration induced by kainic acid in the rat hippocampus, due to its antioxidant profile. In addition, Karim et al. [10], by molecular docking and in vivo approaches, demonstrated anti-amnesic e ffects of nepitrin isolated from *Rosmarinus o*ffi*cinalis* on scopolamine-induced memory impairment in mice. Song et al. [11] demonstrated that a rat model of repetitive mild traumatic brain injury subjected to *Rosmarinus o*ffi*cinalis* extract exhibited improvement of cognitive deficits mediated by its antioxidant and anti-inflammatory profile.

The biological activities of the *Rosmarinus o*ffi*cinalis* could be related to the presence of volatile compounds, such as α-pinene, eucalyptol, and camphor, and phenolic compounds, such as carnosol, carnosic acid, and rosmarinic acid, with proved antioxidant, antibacterial, antifungal, anti-inflammatory, anti-AD, antidepressant and anxiolytic e ffects [18,19]. Therefore, the present study was designed to characterize the chemical components of the *Rosmarinus o*ffi*cinalis* essential oil (REO) and to evaluate the e ffects on anxiety, memory performance, and brain antioxidant status in a scopolamine-induced a zebrafish model of amnesia.
