3.3.1. Hydrogen Peroxide Scavenging Activity (*HPSA*)

Reactive oxygen species (ROS) are chemically reactive oxygen radicals and molecules [superoxide (O2 •−), hydroxyl (•OH), peroxyl (ROO•) and alkoxyl (RO•), HOCl, ozone (O3), peroxynitrite (ONOO−), singlet oxygen (1O2), and H2O2]. They are generated as a natural consequence of biological metabolism. Enzyme systems control ROS levels under physiological circumstances. They have been shown to cause harm to critical biological substances, such as phospholipids, proteins, and DNA. It has been established that the harm they inflict contributes to the development of a variety of illnesses (cancer, cardiovascular disease, atherosclerosis, and Alzheimer's disease) [44]. Even in a condition of physiological health, the harmful consequences of accumulating oxygen and its derivatives in the body contribute to a reduction in life expectancy [45].

The results for hydrogen peroxide scavenging activity (*HPSA*) and inhibition of albumin denaturation (*IAD*) are reported as IC50 values. Ascorbic acid, quercetin, ibuprofen and ketoprofen were utilized as standards. Because it is a function of Rf and is determined using thin-layer chromatography, RM is dimensionless.

The current study focused on hydrogen peroxide scavenging. Hydrogen peroxide is a kind of oxidant that is constantly produced in living tissues as a result of a variety of metabolic activities. However, detoxification is critical in order to keep it from entering hazardous reactions like the Fenton reaction [46].

Ascorbic acid and quercetin were employed as controls. They are natural substances having antioxidant characteristics that have been proven. The values we obtained varied from 59.47 μg/mL to 85.09 μg/mL for the synthesized hybrids (Table 1).

The synthesized ketoprofen analogs had modest activity when compared to ascorbic acid (24.84 μg/mL), but when compared to quercetin, hybrid **3d** had greater activity, while hybrids **3b** and **3c** had activity similar to quercetin (Figure 3).

**Figure 3.** *HPSA* of the newly synthesized ketoprofen hybrid compounds. Ascorbic acid (AA) and quercetin (Qrc) were utilized as standards. *HPSA* results are given as IC50 (μg/mL).

Despite hydrogen peroxide's low level of reactivity, it can harm cells by creating hydroxyl radicals in them [47]. The most reactive radicals are hydroxy radicals, which are considered to be responsible for some tissue damage produced by inflammation. The superoxide anion radical (O2 −•) and H2O2 in living organisms are converted into •OH and •O2, which cause cell damage. The inflammatory process generates a superoxide anionic radical at the site of inflammation, which is coupled with the creation of other oxidizing species, such as •OH. It has been postulated that hydroxyl radical scavengers can function as protectors by lowering inflammation by reducing prostaglandin synthesis. As a result, removing H2O2 is critical in preventing the formation of •OH.
