## 5 Antioxidants from Natural Products as Alternative Treatment
### Quercetin (QC)  
Quercetin (QC), a natural polyphenol abundant in fruits, vegetables, and herbs, has garnered attention for its potent antioxidant properties and potential therapeutic effects in various diseases, including psoriasis [10]. Its ability to strengthen antioxidant defenses against oxidative stress in psoriasis by scavenging free radicals and upregulating antioxidant enzymes has been well-documented [84]. Given that oxidative stress plays a pivotal role in promoting inflammation and abnormal keratinocyte proliferation, quercetin's antioxidant properties position it as a promising candidate for managing psoriasis by targeting these underlying mechanisms [85; 86]. Studies using an miquimol-induced psoriasis-like mouse model have demonstrated QC's potential to offer anti- psoriatic benefits by decreasing PASI scores, alleviating histopathological alterations, and regulating oxidative and inflammatory markers [10]. This study also revealed that quercetin therapy enhances the functions of antioxidant enzymes, including CAT and SOD, while reducing MDA levels [10]. QC has the potential to be used as a natural medicine for the treatment of psoriasis because of its anti-inflammatory and antioxidant qualities [10]. Furthermore, a combination therapy of Cisplatin (cis-dichloramine platinum II) (cDDP) and quercetin has shown promising results, with restored TAS levels and significantly lowered TOS levels indicating QC's ability to alleviate oxidative stress-related disruptions [87].  
Further preclinical research has highlighted the potential benefits of quercetin in treating psoriasis, both topically and through innovative delivery systems. In addition, preclinical research has demonstrated the potential benefit of quercetin in the treatment of psoriasis by improving skin histology and reducing psoriatic symptoms when applied topically [10; 85]. For instance, a study aimed to enhance the solubility and anti- psoriatic activity of QC by isolating it from _Psidium guajara_ leaves and preparing spanlastics has shown promising results [85]. Spanlastics, known for their biodegradable, biocompatible, and non-immunogenic structure, were utilized as a drug carrier, demonstrating a substantial reduction in Psoriasis Area and Severity Index (PASI) ratings and apoptosis-related gene expression after eight weeks of topical QC spanlastics therapy [85; 88]. Using an miquimol (IMQ)-induced mice model, research has examined the therapeutic potential of QC in psoriasis. The results showcased significant improvements in histology, decreases in PASI scores, and modifications of the NF-\(\kappa\)B pathway and pro-inflammatory cytokines [10]. Specifically, QC successfully lowered TNF-\(\alpha\), IL-6, and IL-17 levels, boosted antioxidant enzyme activities, and down-regulated NF-\(\kappa\)B pathway components [10]. Clinical trials evaluating formulations containing quercetin, either alone or in combination with other agents, have shown beneficial effects, including reduced erythema, scaling, and plaque thickness.  
In summary, with its potent antioxidant and anti-inflammatory properties, quercetin holds promise as a therapeutic agent for treating psoriasis. By targeting oxidative stress and inflammation, quercetin addresses key pathological mechanisms underlying psoriasis pathogenesis. Further research, including well-designed clinical trials, is warranted to fully elucidate the therapeutic potential of quercetin in psoriasis management and to establish its optimal dosage, formulation, and long-term safety profile. However, the evidence suggests quercetin as a possible useful addition to the arsenal of psoriasis therapies, providing a safe and effective natural remedy for those suffering from this crippling skin condition.