Viola Odorata Extracts: Phytochemical Profiling, Antioxidant Capacity, Enzyme Inhibition, and COX-2/NOS-2-Mediated Anti-Inflammatory Effects

In the present study, the phytochemical and bio-pharmacological effects of the species Viola odorata were explored. Different polarity extracts, namely water and methanol were assayed for their content in phenolic compounds, enzyme inhibition and scavenging/reducing properties. Additionally, through a validated ex vivo model of colon inflammation, the effects of water and methanol extracts were assayed on Escherichia coli lipopolysaccharide (LPS)-induced up-regulation of both cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (NOS-2) gene expression. The results of the study indicate that methanol extract was the richest in terms of total phenols (37.26 mg GAE/g) and flavonoids (56.90 mg RE/g). Indeed, the methanol extract was the most effective as antiradical (DPPH: 24.91 mg TE/g and ABTS: 66.62 mg TE/g) but also as enzyme inhibitor toward cholinesterases (AChE: 3.23 mg GALAE/g and BChE: 5.02 mg GALAE/g), tyrosinase (133.29 mg KAE/g), glucosidase (0.27 mmol ACAE/g), and amylase (0.82 mmol ACAE/g). Transcription factors regulating NOS2 and COX-2 were used to construct a regulatory network, and five major phytochemicals were screened for target prediction. Selected proteins were subjected to molecular docking, revealing strong interactions between kaempferol-3-O-glucoside and rutin with BChE, NF-κB, and STAT3. The V. odorata extracts were also effective in blunting the LPS-induced gene expression of both COX-2 and NOS-2; thus, confirming enzyme inhibition effects, anti-inflammatory and antioxidant properties. The results suggest that this species is a valuable source of bioactive compounds for developing health-promoting applications.