4. Conclusions

The results presented for the NSAIDs under study pointed out their efficiency as quenchers of photogenerated O2ð 1 ΔgÞ. In Rf-photosensitized processes the dominant mechanism is the O2ð 1 ΔgÞ-mediated, but also other ROS can be intercepted by most of them. The experiments here detailed showed that DFN and IMT can interact with H2O2 and O�<sup>−</sup> <sup>2</sup> whereas MEL is an effective quencher for the latter Rf-photogenerated species.

DNF could be considered as an ideal scavenger of O2ð 1 ΔgÞ, as the oxidative process occurs by a physical mechanism without significant self-degradation of this NSAID. In the case of IMT or oxicams, their protective effect decline along the time. The reason is that these scavengers can also be targets of the oxidation ROS-mediated processes. Even though, the in vivo antioxidant effectiveness would be warranted by daily and prolonged intake. Generally, that is the form of administration in which these analgesics are employed in the treatment of serious detrimental inflammatory illness or chronic pains.

Based on the discussed results, the NSAIDs studied herein present, in principle, promising properties for medicinal use as bio-antioxidants against in situ generated ROS. Nevertheless, great care must be taken because at the same time different negative effects in the human body have been reported [27, 28]. The literature on this topic, in most cases, only mentions rare but possible gastrointestinal adverse effects [29]. In the case of DFN, the reported side effects are not so dramatic, but IMT and MEL have been connected to the pathogenesis of gastric and intestinal mucosal lesions with participation of ROS [30–32]. Those undesired effects must be thoroughly taken into account mainly because of the relative high doses necessary with some of them in order to guarantee the replenishment, ensuring the antioxidant effectiveness against ROS activity.
