Atopic dermatitis (AD) is one of the most common chronic relapsing skin disorders that is characterized by eczematous skin lesions, defective epidermal barrier, inflammation, and it generally appears in infants or young children. The causes of this disease are still under investigation but two common factors that contribute to the pathogenesis of AD are bacterial infection and oxidative stress. Some Vietnamese medicinal plants used in the management of atopic dermatitis, Terminalia catappa, Piper sarmentosum, Psidium guajava, and Piper betle, have been comprehensively investigated for their metabolites as well as the antioxidant activity for many years. However, there has not been any study of antibacterial, antioxidant effects, and phytochemicals of all these plants toward the development of a dermatological product for AD. Herein, our study aimed to evaluate these properties of four plant extracts. A MIC value was reported at 32 µg/mL for all four methanolic extracts against Methicillin-resistant Staphylococcus aureus strains. The antioxidant capacity quantified through DPPH and ABTS tests showed the IC₅₀ ranging from 19.267 ± 0.393 µg/mL (Terminalia catappa) to 3764.278 ± 2.134 µg/mL (Piper sarmentosum). Moreover, the total phenolic and flavonoid content were accessed, showing that Piper betle had the highest level of phenolics/flavonoids, while Piper sarmentosum was the lowest. Since the antioxidant activity and the level of active compounds have a strong interplay, this study also demonstrated the correlation between the results of the antioxidant assay and total phenolic/flavonoid content

Keywords: Atopic dermatitis, Terminalia catappa, Piper sarmentosum, Psidium guajava, Piper betle, Antimicrobial, Antioxidant.