Essential Oil Composition and Biological Activities of Hyptis eriocephala, an Aromatic Lamiaceae Species from Southern Ecuador

Hyptis eriocephala is an aromatic Lamiaceae species from southern Ecuador whose essential oil has not previously been characterized. To establish an initial phytochemical and biological baseline, aerial parts collected at Villonaco were subjected to three independent steam-distillation runs, yielding 0.13 ± 0.04% (w/w) essential oil. Volatile constituents were tentatively assigned by GC–MS using concordant EI mass-spectral and linear retention-index evidence, whereas relative composition was determined by GC–FID peak-area normalization without an internal standard, calibration curves, or response correction factors. Sixty-five constituents accounted for 96.81% of the total GC–FID peak area. The relative profile was dominated by hydrocarbon sesquiterpenes (67.88%), followed by hydrocarbon monoterpenes (24.36%), with α-copaene (28.20 ± 0.24%), germacrene D (9.29 ± 0.09%), α-pinene (6.98 ± 0.03%), α-cubebene (6.70 ± 0.06%), δ-cadinene (6.03 ± 0.07%), limonene (5.44 ± 0.05%), (E)-caryophyllene (5.31 ± 0.05%), and β-phellandrene (4.96 ± 0.02%) were the principal constituents. The oil showed a narrow antibacterial response, with MIC values of 250 µg/mL against Enterococcus faecium ATCC 27270 and 2000 µg/mL against Enterococcus faecalis ATCC 19433. Radical-scavenging activity was assay-dependent: activity was measurable in the ABTS assay (SC50 = 76.87 ± 1.05 µg/mL; TEAC = 30.06 ± 1.16 µM TE/g EO), whereas 50% DPPH scavenging was not reached at 8000 µg/mL. The oil preferentially inhibited BuChE (IC50 = 125.3 ± 1.03 µg/mL) over AChE (IC50 = 385.9 ± 1.02 µg/mL). These findings establish a preliminary phytochemical and biological baseline for the Villonaco material but do not demonstrate a species-wide chemotype, mechanism of action, or therapeutic potential.