Evaluation of Antioxidant and Anti-psoriatic Activities of Purple Sweet Potato (Ipomoea batatas L.) Leaves Aqueous Extract on Imiquimod-induced Psoriasis-like Dermatitis

Psoriasis is a chronic autoimmune skin disease that affects the quality of life. Psoriasis also is one of the most unpredictable and currently incurable diseases. Conventional therapy using corticosteroids, vitamin D analogs, calcineurin inhibitors, and cytotoxic agents is associated with a low success rate, and prolonged use causes side effects. Thus, the discovery of more effective anti-psoriatic drugs with a minimal side effect is currently an active research area. In Malay traditional medicine, the leaf part of sweet potato (Ipomoea batatas) has been claimed as anti-psoriatic. In this study, we evaluated the antioxidant and anti-psoriatic effects of an aqueous extract of purple sweet potato leaves (PSPLAE) on psoriasis-like skin inflammation induced by imiquimod (IMQ) in BALB/c mice. This study examined various antioxidant-related phytochemical components in PSPLAE, specifically the total phenolic content (TPC) and total flavonoid content (TFC). The antioxidant capacity of PSPLAE was assessed utilizing the 2,2-diphenyl-1-picryhydrazyl (DPPH) free radical scavenging method. The plant extract was then applied to an IMQ-induced psoriatic BALB/c mouse model to evaluate the efficacy of PSPLAE against psoriasis-like dermatitis. Treatment was administered topically for 15 d using PSPLAE cream at concentrations of 5, 10, and 20%, and the psoriasis area severity index (PASI) was calculated. In the phytochemical analysis, PSPLAE exhibited the corresponding values of 7.62 ± 1.91 mg GAE/g dry extract (DE), and 2.74 ± 0.85 mg QE/g DE for TPC and TFC, respectively. In addition, the antioxidant activity of PSPLAE, determined by the DPPH assay showed lower activity (EC50 = 244.8 ±13.6 μg/mL) when compared to the ascorbic acid standard (EC50 = 47.3 ±8.9 μg/mL). Interestingly, the antioxidant activity was found positive (r = 0.59) (moderated association) correlated with the TPC. As for the in vivo study, the effect of PSPLAE cream on the IMQ-induced psoriatic mouse model showed a dose- dependent response as evident through the PASI grading. This study demonstrated the anti-psoriatic effects of I. batatas leaf aqueous extract in mitigating IMQ-induced psoriasis-like skin inflammation in BALB/c mice. These findings suggest that I. batatas leaves may serve as a cost-effective source of natural antioxidants with potential anti-psoriatic properties.