Phytochemical Profiling and Evaluation of Antimicrobial and Antioxidant activities of Viola tricolor and the Rare Viola curtisii from Hauts-de-France Region

Plant biodiversity is a rich source of bioactive molecules of pharmaceutical interest, yet it is increasingly threatened by the decline of many species. In this context, the present study focused on two Viola species (Family Violaceae): the wild pansy (Viola tricolor), a common and well-studied species, and the dune pansy (Viola curtisii), a rare, endangered and vulnerable species protected in the Hauts-de-France region. Various extraction methods, including decoction, maceration, ultrasound-assisted extraction, and microwave-assisted extraction with green solvents, were applied to both fresh and dried plant material: aerial part or flowers. The extracts were evaluated for their antimicrobial activities against bacteria, yeasts, and molds, as well as for their antioxidant potential. V. tricolor exhibited antimicrobial activity, particularly against bacteria Escherichia coli and Staphylococcus aureus or the yeast Saccharomyces cerevisiae, with some extracts also active against molds. Extracts from fresh V. curtisii flowers showed strong antibacterial effects, with minimum inhibitory concentrations lower than those of ampicillin used as a reference control. All extracts displayed notable antioxidant activity, with V. tricolor flower extracts showing the highest level. The HPLC-HRMS phytochemical profiling revealed that both species share a similar profile and are rich in flavonoids, including rutin, violanthin, manghaslin and kaempferol derivatives, which likely contribute to their antioxidant activity, while robinin was detected exclusively in V. curtisii flowers. These results highlight the complementarity of the two species, whose bioactive profiles vary with plant material and extraction methods, emphasizing their pharmacological potential and relevance for conservation and valorization of regional plant resources.