**1. Introduction**

Inflammation is the body's response against tissue damage triggered by a variety of endogenous and exogenous stimuli. Its purpose is to remove the harmful agen<sup>t</sup> and restore tissue integrity. The inflammatory reaction involves a series of tissue changes, such as vasodilation with increased blood flow, increased vascular permeability with plasma exudation and protein extravasation, and recruitment of leukocytes in response to cytokines and chemokines. In this context, neutrophils and macrophages, which play critical roles in the early phase of inflammation, also contribute to the development of many chronic inflammatory diseases [1,2].

Inflammatory mediators include a grea<sup>t</sup> diversity oflipids (e.g., eicosanoids), proteins (e.g., cytokines, chemokines, and adhesion molecules) and other chemically related substances that orchestrate various cellular and tissue changes through binding to receptors on leukocytes, endothelial cells, and many other cell types [3]. Some of these mediators are preformed and stored in cytoplasmic granules of mast cells, basophils, and platelets while others circulate as inactive precursors in the plasma. However, most of them are produced directly in response to inflammatory stimuli that may cause severe tissue damage related to the activation of autolytic pathways [4,5]. Persistence of the stimulus, as well as continuous production of inflammatory mediators, cause significant tissue damage, which is associated with morphological and functional changes observed in the pathogenesis of several chronic diseases [6].

Cytokines are notable chemical mediators associated with the development of uncountable inflammatory events. These molecules are produced from gene transcription in immune and non-immune cells, exerting crucial roles in the host defense against pathogens; however, especially in response to severe tissue damage, intense production of cytokines can be potentially harmful [7].

In this context, the tumor necrosis factor (TNF)-α and interleukin (IL) and IL-1 have remarkable local and systemic effects. These cytokines are capable of activating leukocytes and other cell types, stimulating the production of chemical mediators that amplify the inflammatory response [7,8].

Anti-inflammatory compounds, either synthetic or naturally occurring, are substances capable of inhibiting inflammatory events by interfering with signaling cascades associated with the production or action of inflammatory mediators. In most cases, their mechanism of action involves inhibition of enzymes (such as cyclooxygenase (Cox) -2 and 5- lipoxygenase (LO)), receptors or gene transcription. Corticosteroids and Non-Steroidal Anti-inflammatory Drugs (NSAIDs) are the main drug classes used to treat inflammatory symptoms. Nevertheless, they cause severe side effects, indicating the importance of developing novel, safe, and effective anti-inflammatory drugs [6,9].

(+)–Nootkatone (NTK) is a ketone terpenoid belonging to the largest subclass of sesquiterpenes (Figure 1) [10]. This naturally occurring organic compound is found as a component of aromatic species such as Alaskan cedar (*Cupressus nootkatensis* D.Don) and Java (*Cyperus rotundus* L.), as well as in essential oils of *Citrus* (Rutaceae), *Alpinia* (Zingiberaceae), *Chrysopogon* (Poaceae) and many other genera [11]. Due to its pleasant fragrance, this compound, as well as its biogenetic precursor valencene, have been industrially used in the chemical, food, and cosmetic sectors [11,12]. Nevertheless, studies have demonstrated that other components of citrus fruits, such as flavonoids, mainly due to their antioxidant and anti-inflammatory activities, contribute to the relevance of *Citrus* species as sources of natural products with both industrial and medicinal use. Additionally, as flavonoids are abundant in fruit juices, the consumption of these products represents an easy way to take advantage of the therapeutic properties of these compounds [12].

**Figure 1.** (+)-Nootkatone (NTK) [8].

Previous studies demonstrated that plant extracts containing NTK presented anti-inflammatory effects. Tsoyi and collaborators demonstrated that NTK and valencene inhibited nitric oxide (NO) production by inhibiting NO synthase [13]. It was also found that the compound inhibited platelet activation [14] and lipid peroxidation, in addition to inhibiting systemic oxidative stress, as well as preventing DNA damage by activating nuclear factor erythroid-derived 2-like 2 and heme oxygenase 1 [15].

Considering the pharmacological properties of NTK, this study aimed to investigate its e ffects in mice models of acute and chronic inflammation.
