Multiple sclerosis (MS) is defined as an inflammatory neurodegenerative disease of the central nervous system (Frischer et al., 2009). It is estimated that more than 2.8 million people live with MS worldwide, which is the leading cause of non-traumatic neuroglial disease in young adults (Hauser and Cree, 2020; Walton et al., 2020). Consistent with the current worldwide pattern, Iran is experiencing a significant rise in the incidence and prevalence of MS (Abdollahpour et al., 2020). MS pathology was defined initially by the presence of focal white matter lesions, demyelination, reactive astrocytic scar formation, and partial preservation of axons, which the preserved axons would also be affected by the progression of the disease (Lassmann and van Horssen, 2011). In the early stages of the disease, patients experience clinical relapses and remissions. In this stage, inflammatory demyelination causes the formation of focal plaques in the white matter. In the progressive stages, extensive demyelination in the cerebral cortex and the expansion of degenerative changes in white and gray matter are observed (Kutzelnigg et al., 2005).

However, the pathogenesis of MS has not yet been fully elucidated; chronic inflammation and oxidative stress are two of the major hallmarks in the pathogenesis of the disease (Gilgun-Sherki et al., 2004). The inflammatory response in MS lesions mainly consists of activated microglia/macrophages and T-cells and is associated with demyelination and neurodegeneration (Lassmann and van Horssen, 2011). In addition, an inflammatory environment leads to free radicals that exacerbate the inflammatory reaction (Vahid et al., 2023). Reactive oxygen species (ROS) are mainly produced by mitochondria, which contribute to neurodegeneration by lipid peroxidation, as well as protein and DNA oxidation (Kausar et al., 2018). An imbalance between the body's ROS production (oxidants) and antioxidants leads to oxidative stress (Birben et al., 2012). ROS is believed to be involved in the pathogenesis of MS lesions through several underlying mechanisms, such as inducing myelin phagocytosis, neuronal and axonal injury, as well as oligodendroglial damage (Ortiz et al., 2013). Clinical studies show that oxidized phospholipids and malondialdehyde (MDA) are excellent biomarkers for assessing neuro and glial degeneration (Peña-Bautista et al., 2019).

On the other hand, studies show that the prevalence of depression among patients with MS is 50%, which is higher than other neurological diseases (Feinstein, 2004). Furthermore, the rate of depression among these patients is 3 to 10 times higher than that in the general population (Patten et al., 2017). The poor mood in these patients is usually accompanied by discouragement, irritability, and frustration (Feinstein, 2011). A part of depression and anxiety in MS patients has been attributed to chronic inflammation and oxidative stress (Katarina et al., 2020; Morris et al., 2018).

In this regard, studies, in addition to conventional treatments, have tried to modify the inflammation and oxidative stress in these patients by using bioactive food compounds and dietary interventions as complementary therapies (Bhatti et al., 2023; Miller et al., 2019). Studies have also shown that anti-inflammatory and pro-antioxidant diets, including food items such as fruits and vegetables rich in fiber and antioxidants and nutrients such as vitamin D, polyunsaturated fatty acids (PUFA), and spices including ginger, saffron, and turmeric, are associated with a decreased risk of MS (Abdollahpour et al., 2020, 2022).

The dried, red stigmas of saffron from the Iridaceae family (Crocus sativus L.) have been used in various cuisines, including Iranian, and were mentioned as a traditional herb in various references (Korani et al., 2019; Zeinali et al., 2019). Accumulating body of evidence shows that saffron supplementation could provide anti-depressant (Hosseini et al., 2018; Musazadeh et al., 2022), neuroprotective (Bian et al., 2020), neurocognitive (Avgerinos et al., 2020), and anxiolytic effects (Hosseini et al., 2018; Jackson et al., 2021). Saffron contains several active ingredients, including crocin, crocetin, safranal, and picrocrocin (Hosseini et al., 2018). Crocin (trans-crocetin bis(β-d-gentiobiosyl) ester) is a water-soluble carotenoid and the bioactive compound of saffron with potent antioxidant and anti-inflammatory functions (Hashemzaei et al., 2020). The protective role of crocin in managing neurodegenerative diseases has been previously shown (Farkhondeh et al., 2018). In addition, crocin decreased levels of thiobarbituric acid reactive substances (TBARS) and nitrite in the hippocampus and improved aversive memory in animal models of Parkinson's disease (Rajaei et al., 2016). Crocin also decreases oxidative stress and ROS by throbyulating the expression and activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and glutathione peroxidase (GPx) (Hashemzaei et al., 2020). Injection of crocin into BALB/c mice decreased the neurological effects of mild traumatic brain injury (rmTBI) by suppressing inflammation and oxidative stress (Salem et al., 2022). Some studies have investigated the anti-inflammatory effects of crocin in MS patients. In two randomized control trial (RCT) studies, treating patients with 30 mg/day crocin for 4 weeks improved oxidative stress and inflammatory biomarkers (Ahmadi et al., 2020; Ghiasian et al., 2019). However, the duration of their intervention was only 4 weeks, and the possibility of longer-term effects and mental health effects have not been investigated. In addition, the role of crocin in the improvement and management of mental health in patients under methadone treatment has previously been reported (Ghaderi et al., 2019).

Considering the link between oxidative stress and inflammation and pathogenesis of MS and the potential mental health management, the anti-oxidative and anti-inflammatory effect of crocin, and the lack of mid/long-term interventions considering all these aspects, we aimed to conduct an RCT to investigate the protective effects of this bioactive compound on patients with MS. We hypothesized that crocin would modify inflammation, oxidative stress and improve mental health status including depression and anxiety.