Chronic obstructive pulmonary disease (COPD) is a progressive and chronic respiratory disorder characterized by reversible airflow limitation and destruction of lung parenchyma (Decramer et al., 2012). Various factors are involved in the development and progression of COPD, such as sex, age, genetic factors, chronic bronchitis, exposure to particles, and infection (Halpin et al., 2021). Smoking is a predominant risk factor in patients with COPD, as it contains various harmful substances that stimulate reactive oxygen species (ROS) production and induce oxidative damage (Bernardo et al., 2015). Although the pathophysiological mechanism of COPD has not been well clarified, certain factors have been reported, including neutrophil airway inflammation, oxidative stress, protease–antiprotease imbalance, and apoptosis (Amani et al., 2017; Barnes, 2017; Ghobadi et al., 2017).

Oxidative stress is caused by an imbalance in ROS-induced oxidants and endogenous antioxidants (Marotta et al., 2011). Environmental sources for ROS production include cigarette smoking, car exhaust fumes, industrial pollution, and occupational exposure to dust (Antunes et al., 2021). In contrast, cellular sources for ROS production include activation of xanthine oxidase (XO) and nicotine adenine disphosphonucleotide (NADPH) oxidase (Taniguchi et al., 2021). Inflammation of the airways is closely related to oxidative stress processes in COPD patients. ROS-induced airway inflammation leads to the recruitment of inflammatory cells to the airways and the production of pro-inflammatory cytokines, which increase the severity of inflammation and increase ROS production (Kirkham and Barnes, 2013). Transcription factors such as nuclear factor kappa B (NF-kB) play a significant role in the interaction between inflammation and ROS in chronic inflammatory diseases (Mahmoud et al., 2021). Therefore, one of the critical therapeutic targets of COPD patients is the management of inflammation and oxidative stress.

Therapeutic use of some foods and herbs has been of interest to humans throughout history for the prevention and treatment of diseases and health problems (Boskabady et al., 2007; Ghasemi et al., 2021; Khazdair et al., 2021; Saadat et al., 2021). Saffron (Crocus sativus L.) is a valuable plant used as a food additive and medicinal plant (Boskabady and Aslani, 2006). Therapeutic effects of saffron have been reported in various disorders such as cardiovascular, asthma, diabetes, and autoimmune (Hashemzaei et al., 2020; Aslani et al., 2021). Major compounds of saffron include crocin, crocetin, safranal and picrocrocin (Kermani et al., 2017a; Saadat et al., 2019). The antioxidant and anti-inflammatory properties of crocin have been proven in animal and human studies (Kermani et al., 2017a; Aslani et al., 2021). In chronic inflammatory diseases such as diabetes and asthma, clinical studies have reported the protective role of saffron in reducing inflammatory markers (Hosseini et al., 2018; Shahbazian et al., 2019). Recently, Krocina™ tablets, a 98% purified crocin from saffron, have been used in clinical trial studies (Poursamimi et al., 2020). The anti-inflammatory effects of Krocina™ have been identified in patients with osteoarthritis by reducing C-reactive protein (CRP) and interleukin (IL)-17 levels (Poursamimi et al., 2020).

Accordingly, the primary aim of the current study was to evaluate the effects of 12 weeks of crocin from saffron intervention on oxidant/antioxidant and inflammatory markers in COPD patients. Secondary objectives were determined for exercises capacity and pulmonary function tests (PFTs).

The most important results of the current clinical trial study were: one- decreased serum TOS and NF-kB levels, two- increased serum TAOC levels, and three- improved 6MWD tolerance.

COPD is an inflammatory disease characterized by the involvement of the lung parenchyma, airways, and pulmonary vasculature (Halpin et al., 2021). The pathophysiology of COPD is thought to be involved in oxidant/antioxidant and protease/antiprotease imbalances (Boukhenouna et al., 2018). As a result of increased activity of oxidants and proteases, destruction of air sacs has been reported in patients with COPD (Boukhenouna et al., 2018). PFT changes are critical diagnostic, grading and monitoring criteria for COPD patients (Halpin et al., 2021). There is evidence of a decrease in FEV1 in COPD patients due to inflammatory responses and airway obstruction. The intervention with Crocin showed that FEV1 in COPD patients was enhanced, although it was not significant. One of the factors that may have influenced the PFT results of the current study is the duration of the intervention for 3 months. The effectiveness of most supplements has been reported in clinical trial studies with more than 3 months of intervention. Hosseini et al. demonstrated that saffron intervention improves pulmonary function tests in asthmatic patients (Hosseini et al., 2018). Although the exact mechanism of saffron and its active ingredient (Crocin) is poorly understood, its anti-inflammatory and antioxidant effects may play a key role (Kermani et al., 2017b). Most animal studies have shown the protective effects of saffron and Crocin in the ovalbumin-induced asthma model (Saadat et al., 2019; Aslani et al., 2021). However, further human studies are required to elucidate the effects of Crocin on PFTs in chronic lung diseases.

Oxidative stress is a critical factor in promoting COPD inflammation (Zinellu et al., 2021). Oxidative stress occurs when endogenous antioxidant defenses are impaired, or reactive oxygen species (ROS) activity is enhanced (Kirkham and Barnes, 2013). ROS production originates from environmental (cigarette smoke) or cellular (inflammatory and structural cells) sources (Kirkham and Barnes, 2013). Pulmonary inflammation induced by ROS leads to the production of pro-inflammatory markers and the recruitment of inflammatory cells into the airways, thereby increasing the production of ROS (Zinellu et al., 2021). In patients with COPD, oxidative stress is typically caused by prolonged exposure to cigarettes smoke or by a variety of inflammatory and immune stimuli in the airways (Taniguchi et al., 2021). Elevated levels of oxidants and decreased antioxidant levels are present locally (in lung tissue) and systemically in patients with COPD (Elmasry et al., 2015). Patients with COPD showed increased levels of oxidative products such as malonyl dialdehyde (MDA) and TOS compared to healthy subjects (Zeng et al., 2013). Decreased antioxidants may also contribute to increased oxidative stress in COPD conditions, such as SOD, GSH-Px, reduced GSH, TAOC, thioredoxin, and nuclear factor erythroid two– related factor 2 (Nrf2) (Taniguchi et al., 2021).

The study showed that Crocin treatment in COPD patients caused a significant reduction in serum TOS levels. On the other hand, Crocin treatment also increased TAOC levels in COPD patients. In fact, the results suggest that Crocin treatment reversed the oxidant/antioxidant imbalance created by COPD. Saffron has potent anti-inflammatory and antioxidant effects with various components such as Crocin, crocetin, and safranal (Assimopoulou et al., 2005). Invitro, in vivo, and human studies have shown the antioxidant effects of saffron and Crocin in various pathological conditions, including asthma, COPD, myocardial infarction, and cancer (Tsantarliotou et al., 2013; Al-Gubory, 2014). The saffron and its effective compounds exert their antioxidant effects by reducing the production of oxidative factors such as MDA, lipid peroxidation (LPO), inducible nitric oxide synthase (iNOS), nitric oxide (NO), XO, myeloperoxidase (MPO), and protein carbonyls (PC) as well as by increasing antioxidant factors such as reduced glutathione (GSH), total antioxidant capacity (TAOC), superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), and glutathione-S-transferase (GST) (Boskabady and Farkhondeh, 2016).

Different clinical trial studies have examined the effects of saffron on oxidative markers in various diseases. Intervention with saffron in type 2 diabetic patients reduced serum MDA concentrations while no effect was observed on TAOC and F2-isoprostane levels (Azimi et al., 2014; Ebrahimi et al., 2019; Shahbazian et al., 2019). In patients with ulcerative sclerosis, it was revealed that intervention with saffron for 8 weeks resulted in increased TAOC, GPX, and SOD while preventing an increase in serum MDA concentration compared with the placebo group (Tahvilian et al., 2021). Also, in patients with multiple sclerosis, a 4-weeks intervention with saffron decreased MDA levels and increased TAOC (Ghiasian et al., 2019). In addition, similar results occurred in patients with nonalcoholic fatty liver diseases due to intervention with saffron for 12 weeks, decreasing MDA and increasing TAOC levels (Pour et al., 2020). In patients with metabolic syndrome, it has been reported that intervention with saffron for 12 weeks can modulate pro-oxidant-antioxidant serum levels (Kermani et al., 2015). However, in patients with rheumatoid arthritis, Hamidi et al. did not observe significant differences in MDA and TAOC levels after 12 weeks of saffron intervention (Hamidi et al., 2020). For the first time in a clinical trial study on COPD patients, the results of our study reported the reducing effects of Crocin on oxidative factors and the increasing effects of antioxidant factors.

Recently, there has been much evidence that oxidative stress and inflammation play a vital role in the pathogenesis of various diseases, including diabetes, cancer, obesity, metabolic syndrome, and chronic respiratory disease (Mahmoud et al., 2021). By activating inflammatory signaling pathways, ROS causes the release of different inflammatory mediators such as cytokines, chemokines, and eicosanoids (Mahmoud et al., 2021). Activation of some protein kinases and signaling pathways (nuclear factor-kappaB (NF-kB), p38 mitogen-activated protein kinases (MAPK), and protein kinase C) as a result of oxidative stress also has a double effect on inflammatory processes (Canty et al., 1999; Khan et al., 2020). NF-κB activation in patients with COPD occurs in response to inflammatory mediators such as IL-1β and TNF-α or due to activation of Toll-like receptors (TLRs) following bacterial or viral infections (Edwards et al., 2009). The redox pathway regulates NF-κB signaling due to oxidant/antioxidant imbalance in inflammatory diseases of the airways (Rajendrasozhan et al., 2008). In patients with COPD, regulation of NF-κB signaling activity is one of the essential therapeutic criteria, so the therapeutic use of corticosteroids inhibits NF-κB activity and consequently reduces the levels of inflammatory cytokines.

The present study showed that the Crocin intervention had a protective effect on the serum NF-κB concentration since there was a significant increase in the placebo group at the end of the study. Also, the mean changes in serum NF-κB concentration in the placebo group were higher than in the Crocin-treated group. The results revealed that Crocin intervention had inhibitory effects on NF-κB activity in patients with COPD. Similar results have been reported from human and animal studies about the effects of saffron and Crocin on NF-κB levels (Boskabady and Farkhondeh, 2016). Saffron and crocin exert anti-inflammatory and antioxidant effects through various mechanisms, including modulation of phosphoinositide-3-kinase (PI3K)/Akt, protein kinase C (PKC), mitogen-activated protein kinases (MAPK/ERK), Nrf2, NF-κB p65, c-Jun N-terminal kinases (JNK), Ca2+/calmodulin dependent protein kinase 4 (CAMK4), inducible nitric oxide synthase (iNOS), signal transducer and activator of transcription 6 (STAT6), ER-stress markers, and high-mobility group box 1 (HMGB-1) pathways (Kim et al., 2014; Xiong et al., 2015; Yosri et al., 2017; Dianat et al., 2018; Xie et al., 2019; Zhang et al., 2020; Aslani et al., 2021).

One of the most critical health indicators is cardiorespiratory preparations (Oliveira et al., 2016). n exercise test below the maximum 6-min walk-in for patients with COPD is a crucial activity for assessing cardiovascular and respiratory rehabilitation. With this test, patients’ exercise capacity and health-related quality of life (HRQL) can be evaluated (Wouters et al., 2020). COPD patients have reported reduced levels of 6MWD and quality of life compared with healthy individuals (Puhan et al., 2008). Intervention with Crocin for 12 weeks significantly increased 6MWD in patients with COPD. Crocin with anti-inflammatory and antioxidant effects may have led to increased exercise capacity and quality of life satisfaction in patients with COPD, which requires further studies.

This study had some limitations. First, the current study had no female patients, and the extraction results can only be used in men with COPD. Second, the sample size was moderate considering the COVID-19 conditions and may have masked the significant results of crocin. Finally, although most studies have reported duration of ≥12 weeks for saffron (crocin) supplementation, it is advisable to evaluate a more extended intervention with saffron in future studies.

In summary, the association between oxidative stress and inflammation affects patients with COPD, such as decreased pulmonary function tests, exercise capacity, and quality of life. Under COPD conditions, increased oxidative and inflammatory markers (such as TOS and NF-kB) combined with decreased antioxidant factors (TAOC) may have been associated with decreased exercise capacity and PFT. Intervention with Crocin (one of the main compounds of saffron) increased exercise capacity and PFTs of patients with COPD, possibly by modulating oxidant/antioxidant and inflammatory pathways.