Antimicrobial activity of Vepris salicifolia leaf essential oil and δ-cadinene: in vitro evaluation and in silico mechanistic insights into δ-cadinene.

BACKGROUND: The emergence of antimicrobial resistance has intensified the search for new bioactive compounds from natural sources. This study investigated the chemical composition and antimicrobial activity of the essential oil (EO) extracted from the leaves of Vepris salicifolia (Engl.) Mziray. In addition, the molecular interactions and drug-like properties of δ-cadinene, the major constituent of the EO, were evaluated. METHODS: The EO was extracted by hydrodistillation and subsequently characterized chemically using gas chromatography-mass spectrometry (GC-MS). The antibacterial and antifungal activities of the EO and δ-cadinene were assessed using disc diffusion and agar dilution assays, while molecular docking and ADMET analyses were performed to elucidate the potential mechanism of antimicrobial action and evaluate the pharmacokinetic and drug-likeness properties of δ-cadinene. RESULTS: GC-MS analysis identified 26 compounds, representing 84.3% of the EO. The predominant constituents were δ-cadinene (23.5%), intermedeol (18.3%), germacrene D (10.2%), α-muurolol (9.0%), and germacrene D-4-ol (7.5%). The EO and δ-cadinene effectively inhibited the growth of a wide range of Gram-positive and Gram-negative bacteria and fungi. Notably, δ-cadinene showed antibacterial activity against S. aureus ML267, with an inhibition zone of 17.8 mm, comparable to that of ciprofloxacin (18.0 mm). Furthermore, the EO exhibited greater antifungal activity against Penicillium notatum, with an inhibition zone of 14.0 mm compared with 11.0 mm for griseofulvin. Docking results showed favorable binding energies for δ-cadinene with the CrtM enzyme of S. aureus (- 7.757 kcal/mol) and the CYP51 enzyme of P. notatum (- 5.756 kcal/mol). ADMET studies further revealed that δ-cadinene has favorable drug-like characteristics, including high intestinal permeability and oral bioavailability, and did not predict any cardiotoxicity. CONCLUSION: The findings of this study indicate that V. salicifolia leaf EO, particularly δ-cadinene, represents a promising source of antimicrobial agents for future medicinal applications. Nevertheless, the predicted molecular mechanisms of δ-cadinene should be validated through enzyme inhibition assays.