Inflammation acts as a key biological phenomenon in response to infection, trauma, and injuries of body cells or tissues. A successful inflammatory response eliminates the invading pathogens, initiates wound healing and angiogenesis [1]. Based on the severity of outcomes and the duration of actions, it can be categorized into two primary groups. Acute inflammation manifests as swelling, pain, redness and fever, and it is a short-term action that nearly results in healing and is characterized by the emigration of leukocytes into the damaged region. Chronic inflammation is often accompanied by serious diseases, such as chronic obstructive pulmonary disease (COPD), diabetes, tumors and rheumatoid arthritis [[2], [3], [4]]. Generally, moderate inflammation may be beneficial, but persistent inflammation can result in various adverse effects, such as tissue damage, decreased function, formation of tumors, and ultimately death [[5], [6], [7]]. Medications prescribed to treat acute and chronic inflammatory conditions inhibit physiological mechanisms that play a role in the development and manifestations of inflammation.

Organisms initiate inflammatory responses in reaction to a variety of stimuli, such as physical, chemical, and biological factors, leading to the mobilization of innate immune and inflammatory cells to the area of injury or infection [8]. Under extracellular stimulation, macrophages possess the ability to generate and discharge pro-inflammatory mediators, including prostaglandin E2 (PGE-2), NO, interleukin-1 beta (IL-1β), TNF-α, and additional inflammatory mediators [9]. Multiple research investigations have demonstrated that the NF-κB and MAPKs pathways play a crucial role in the regulation of inflammation [10]. Currently, the most commonly prescribed medications for inflammation are nonsteroidal anti-inflammatory drugs (NSAIDs) and steroidal anti-inflammatory drugs (SAIDs). Among them, celecoxib (1), meloxicam (2), ibuprofen (3) and indomethacin (4) are NSAIDs, while hydrocortisone (5), dexamethasone (6), methylprednisolone (7) and beclomethasone dipropionate (8) are glucocorticoids (Fig. 1) [[11], [12], [13]]. However, numerous studies have indicated that prolonged utilization of these anti-inflammatory medications frequently results in negative side effects, such as immunodeficiency, hepatotoxicity, osteoporosis, gastric ulcer and cardiovascular risk, owing to the over production of pro-inflammatory mediators [[14], [15], [16], [17]]. Complications associated with the use of steroidal anti-inflammatory drugs limited their clinical use. As a result, studying anti-inflammatory medications that offer minimal side effects and exceptional selectivity has emerged as a hot research topic in this field.

Steroids, an important class of polycyclic molecules and widely distributed in plants, fungi, marine sponges and yeasts, are components of cell membranes, signaling molecules and are a type of secondary metabolites [18,19]. They play an important role in regulation of many processes in human body ranging from regulating physiological processes and targeting disease-related biological sites [20]. Furthermore, there are many other activities mentioned in the literature, such as antimicrobial [[21], [22], [23]], anticancer [24,25], neuroprotective [26,27], antidiabetic [28] and anti-inflammatory [[29], [30], [31], [32]]. The alteration of functional groups can be achieved by making changes to the steroid ring system and its side chain through chemical modification, and such synthetic alterations lead to establishment of numerous structure activity relationships and thus attracted a great deal of attention as their preparation itself is stimulating challenge to the organic chemists, often demanding development of new and generally useful reactions [33].

Steroid-based medications continue to be one of the most widely marketed classes of pharmaceuticals and offer a wide range of clinical uses [34]. Recently, there has been a significant focus on the modified structure of steroids, specifically the integration of heterocycles into the core of the steroid [35,36]. The most promising heterocyclic compounds are pyrazoles, which are five-membered nitrogen heterocycles [37]. Heterocyclic steroids revealed potent bioactivity as the incorporation of the fused heterocyclic ring into the steroid skeleton improves the biological properties [[38], [39], [40], [41], [42]]. Over the years, numerous steroid analogues modified with nitrogen have been created and produced with the intention of enhancing biological effectiveness and selectivity, and reducing adverse reactions. Numerous of these hybrids exhibit encouraging anti-inflammatory properties, particularly those containing heterocyclic moieties at the C17 position. A steroid derivative in which ring D is modified to introduce a heterocyclic ring has great pharmaceutical significance [43]. Steroids and steroid derivatives have attracted more attention by drug design scientists in recent years to find use in anti-inflammatory treatment.

Moreover, multiple research articles have demonstrated that steroid molecules that contain heteroatoms in both the A- and D-rings exhibited a diverse array of biological effects [[44], [45], [46]]. As a result, a variety of heterocyclic units such as pyrazolines, isoxazolines, and thiazoles were introduced into the steroidal backbone. Steroids having pyrazole, triazole, thiazole and indole entity have been proved to play a significant role in drug discovery. Dihydropyrazole is an important heterocyclic compound have been widely used in the field of medicine because of their high efficiency, low toxicity, and the multidirectional transformation of their ring substituents [[47], [48], [49], [50], [51]]. In addition, many thiazolinone derivatives show strong biological activity and low toxicity, however, there are few reports on the design and synthesis of steroid compounds containing dihydropyrazole and thiazolinone. The dihydropyrazole ring substructure combined with the two may show synergistic anti-inflammatory effects.

Throughout the past 20 years, molecular hybridization has been crucial to the drug discovery process. Therefore, it is evident that the pharmaceutical industry will directly benefit from new hybrid compounds that have pharmacological interest [52,53]. Due to prevalence of steroids and dihydropyrazole as well as thiazolinone in numerous biological and chemical applications, we are attracted by the possibility of coupling both entities to provide valuable dihydropyrazole and thiazolinone linked steroidal compounds. In view of the previous rationale and in continuation of our work aiming at synthesizing heterocycle incorporated steroidal derivatives. For a considerable period of time, our team has focused on the synthesis of novel steroidal derivatives and evaluation of their anti-inflammatory effectiveness. Based on this, we introduced dihydropyrazole and thiazolinone into steroid derivatives, designed and synthesized a new family of steroidal dihydropyrazole thiazolinone derivatives, expecting to have high selectivity and low toxicity. Herein, we report a very simple and high yielding synthesis of steroidal dihydropyrazole thiazolinone derivatives located on D ring, starting from pregnenolone with aromatic aldehydes and thiosemicarbazide in the presence of sodium hydroxide as a catalyst to obtain derivatives 11a∼11q. And the thiazolinone derivatives 12a∼12q were synthesized via the reaction between thioamide derivatives 11a∼11q and chloroacetic acid in acetic acid as the later step, aiming to identify new steroid-based anti-inflammatory agents. The anti-inflammatory abilities of these novel molecules and their underlying mechanisms were evaluated in RAW 264.7 cells. The findings indicated that compound 12e exerted the most potent activity in inhibiting the production of NO without causing obvious cytotoxic effects, effectively suppressed the production of inflammatory mediators such as iNOS, COX-2, TNF-α and IL-6 in LPS-induced RAW 264.7 cells, which are associated with a down-regulation of NF-κB/MAPKs signaling pathways.