Abstract
ABSTRACT
Fungal and oomycete phytopathogens account for 10%–20% of annual global crop losses, and the escalating resistance to synthetic fungicides has intensified demand for plant‐derived alternatives. The essential oil (EO) of
Clinopodium nepeta
(L.) Kuntze, obtained by hydrodistillation from aerial parts harvested in northeastern Morocco, was profiled by gas chromatography–mass spectrometry (GC–MS) and evaluated for antifungal and anti‐oomycete activity against
Verticillium dahliae
,
Phytophthora infestans
, and
Macrophomina phaseolina
using broth microdilution minimum inhibitory concentration (MIC) assays. The EO was dominated by two oxygenated monoterpene ketones, pulegone (42.16%) and menthone (41.43%), which were additionally evaluated as isolated compounds. The whole EO yielded MIC values of 31.25 µg/mL (
P. infestans
), 62.5 µg/mL (
V. dahliae
), and 125 µg/mL (
M. phaseolina
). Both isolated constituents outperformed the native matrix by 2‐ to 16‐fold, revealing antagonistic interactions within the complex EO. Pulegone showed superior activity against
V. dahliae
and
P. infestans
, while menthone was more potent against
M. phaseolina
, a selectivity pattern consistent with the greater electrophilic reactivity of pulegone's α,β‐unsaturated ketone (Michael acceptor) moiety. These findings identify pulegone and menthone as priority biopesticide candidates, pending formulation optimization, in planta validation, and toxicological assessment of pulegone under field‐exposure conditions. Because the GC–MS analysis was performed on an achiral stationary phase, the enantiomeric composition of the oil was not determined; its constituents are therefore reported without stereodescriptors, and the compounds assayed as isolated agents were the commercial reference standards (R)‐(+)‐pulegone and (2S,5R)‐(−)‐menthone. The structure–activity relationship described here is consequently constitutional rather than configurational.