Maple water (Acer saccharum sap), a traditional North American beverage: anti-inflammatory activity and potential functional relevance for skin health

Maple water (Acer saccharum sap) is a traditional seasonal beverage consumed in North America; however, its functional relevance as a bioactive dietary resource remains poorly understood. This study evaluated the anti-inflammatory and skin-protective effects of maple water extract, aiming to bridge traditional consumption with modern functional interpretation. In RAW264.7 macrophages, maple water extract inhibited lipopolysaccharide (LPS)-induced nitric oxide production without cytotoxicity and reduced the expression of key pro-inflammatory mediators, including inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin (IL)-1β, and IL-6, through modulation of nuclear factor-kappa B (NF-κB) signaling. In UV-irradiated HaCaT keratinocytes, maple water extract attenuated cytotoxicity, reduced intracellular reactive oxygen species (ROS), and decreased IL-6 expression, suggesting modulation of oxidative stress and inflammatory responses. Furthermore, maple water extract modulated matrix metalloproteinases (MMP-1 and MMP-2) and their tissue inhibitors (TIMP-1 and TIMP-2), while increasing the expression of epidermal differentiation markers, including filaggrin, involucrin, and loricrin. Maple water extract also influenced hydration-associated responses through the regulation of hyaluronidase and hyaluronan synthase expression. Collectively, these findings suggest that maple water, as a traditional dietary beverage, may contain bioactive components that contribute to the modulation of inflammation, oxidative stress, and skin barrier function, thereby providing a potential functional basis for its traditional consumption.