Ultrasound‐assisted enzymatic extraction of citrus pomace yields dietary fiber‐rich extract with skin‐protective effects

BACKGROUND: Citrus pomace is an abundant byproduct of citrus juice processing and represents a sustainable source of dietary fiber and bioactive polysaccharides. The present study aimed to valorize citrus pomace through ultrasound-assisted enzymatic extraction (UAEE) and to evaluate the protective effects of the resulting extract obtained by Celluclast® treatment with ultrasound pretreatment (CCU) against particulate matter (PM)-induced skin damage. RESULTS: UAEE markedly improved the extraction yield of citrus pomace extract, with CCU showing a higher yield (55.17%) than distilled water extraction (15.67%) and Celluclast® extraction without ultrasound pretreatment (54.00%). CCU also showed the highest dietary fiber recovery based on extraction yield. In PM-stimulated HaCaT keratinocytes, CCU increased cell viability from 75.26% to 94.12% and reduced intracellular reactive oxygen species production in a concentration-dependent manner. CCU further suppressed PM-induced pro-inflammatory responses by reducing tumor necrosis factor-α, interleukin-1β and interleukin-6 levels, as well as inducible nitric oxide synthase and cyclooxygenase-2 protein expression. In addition, CCU restored the expression of skin barrier-and hydration-related proteins, including filaggrin, loricrin, involucrin and hyaluronic acid synthase 1. In vivo, oral administration of CCU also alleviated PM-induced inflammation and water loss in mouse skin. CONCLUSION: These findings demonstrate that UAEE is an effective approach for converting citrus pomace into a dietary fiber-rich functional extract with anti-inflammatory and skin barrier-protective properties. CCU may therefore serve as a value-added ingredient for nutraceutical or skin-health-related functional applications.