Plant biodiversity as a source of protective strategies against oxidative and inflammatory damage: the case of Salix apennina A.K. Skvortsov

Chronic low-grade inflammation and oxidative stress are closely interconnected processes that contribute to progressive cellular dysfunction and represent key biological features of inflammaging. Their reciprocal amplification can impair cellular defence mechanisms and tissue homeostasis, supporting the search for bioactive compounds able to counteract oxidative and inflammation-related damage. In this context, medicinal plants represent a valuable source of phytochemicals with potential antioxidant, cytoprotective and inflammation-modulating properties. Nevertheless, many endemic Mediterranean species remain largely unexplored, limiting the potential exploitation of plant biodiversity for the identification of novel bioactive resources. Salix apennina A.K. Skvortsov is an endemic Italian willow whose phytochemical composition and biological properties are still poorly characterized, despite the recognized medicinal relevance of the genus Salix. The present study aimed to provide the first integrated phytochemical and biological characterization of extracts obtained from the aerial parts of S. apennina, focusing on their ability to counteract oxidative and inflammatory cellular alterations. Particularly, a crude ethanolic extract (SAE) and its aqueous (SAQ) and lipophilic (SAP) fractions were evaluated for polyphenol, flavonoid and tannin contents, antioxidant activity and cellular cytotoxicity. Radical scavenging, metal-chelating and antiglycation properties were investigated through DPPH, ABTS, ferrozine and advanced glycation end-product formation assays. Based on its overall phytochemical and biological profile, SAQ was selected for further chemical characterization by HPTLC and GC-MS analysis and for biological investigations in epithelial cell models exposed to tert-butyl hydroperoxide (t-BOOH)-induced oxidative stress or IL-6-induced inflammatory conditions. Its effects on epithelial barrier integrity and on the redox-sensitive transcription factor Nrf2 were also investigated. SAE and SAQ were characterized by higher polyphenol, flavonoid and tannin contents than SAP and displayed the strongest antioxidant properties. Among the investigated samples, SAQ showed a favorable cellular tolerability profile and counteracted t-BOOH-induced oxidative alterations. Moreover, SAQ attenuated cellular alterations induced by IL-6, preserved epithelial barrier integrity and increased cellular Nrf2 levels. Overall, these findings provide the first evidence of the biological properties of S. apennina and highlight its aqueous fraction as a promising source of bioactive phytochemicals able to modulate oxidative and inflammatory processes. These results support further investigation of this underexplored willow species as a potential source of compounds of nutraceutical interest in the context of inflammation- and oxidative stress-related cellular dysfunctions.