Wild Nepeta sibirica L. from Eastern Kazakhstan: Botanical Characterization, Essential-Oil Composition, Chemogeographic Context, and Preliminary Bioactivity

Nepeta sibirica L. is a medicinal and aromatic species of Lamiaceae whose volatile chemistry varies across its Eurasian range. In this study, we integrated voucher-anchored botanical characterization, GBIF-supported distributional context, essential-oil composition, chemogeographic comparison, and preliminary bioactivity assessment of a wild population from the Altai–Tarbagatai Ridge, Eastern Kazakhstan. Hydrodistillation yielded 0.3% (w/w) essential oil. GC–MS analysis of the essential oil detected and tentatively identified 62 volatile constituents, accounting for 95.5% of the total composition. A dominant nepetalactone peak represented 70.6% of the oil and was tentatively assigned as cis–trans-nepetalactone based on electron-ionization mass-spectral and retention-index data obtained on an achiral column. Germacrene D (6.5%) and cis-β-ocimene (2.8%) were the principal secondary constituents. Chemogeographic comparison indicated similarity to previously reported nepetalactone-rich material from the Altai region. The essential oil exhibited limited DPPH radical-scavenging activity, reaching a maximum inhibition of 12.88 ± 0.56% at 24.19 µg/mL; an IC50 could not be determined within the tested concentration range. In the Artemia salina assay, the essential oil caused 100% mortality at all tested concentrations (0.01–0.10 mg/mL) after 24 h, precluding LC50 estimation within the tested range. These findings document a nepetalactone-dominant essential-oil profile in a voucher-confirmed wild population of N. sibirica from Eastern Kazakhstan and provide preliminary quantitative data on its DPPH radical-scavenging activity and A. salina lethality.