Phytochemical Composition and Bioactivity of Elsholtzia strobilifera (Benth.) Benth Essential Oil With Spectral Characterisation of Pinocarvone Using NMR Techniques

Abstract

Species of the genus Elsholtzia (Lamiaceae) have been traditionally used in folk medicine and are known for their diverse biological properties. However, the chemical composition and bioactivity of the essential oil from Elsholtzia strobilifera (Benth.) Benth. remain insufficiently explored. The present study aimed to investigate the chemical composition of the essential oil of E. strobilifera, isolate its major constituent, and evaluate its antioxidant, antimicrobial, nematicidal, and egg-hatching inhibition activities. The essential oil was analysed using GC and GC–MS techniques. The major constituent was isolated by column chromatography and characterised through spectroscopic analyses, including ¹H NMR, ¹³C NMR, DEPT, HMBC, and COSY experiments. Antioxidant activity was assessed using DPPH and hydrogen peroxide scavenging assays, while antimicrobial activity was evaluated against four bacterial and four fungal strains. Nematicidal and egg-hatching inhibition activities were also determined. GC and GC–MS analysis identified 43 compounds representing 95.28% of the total oil composition. The major constituents were pinocarvone (40.0%), β-bisabolene (9.2%), and β-curcumene (6.05%). The essential oil exhibited significant antioxidant activity with IC₅₀ values of 21.52 μL/mL and 25.31 μL/mL in DPPH and hydrogen peroxide scavenging assays, respectively. Antimicrobial studies showed inhibition zones ranging from 20.0 ± 0.5 to 26.0 ± 0.02 mm against bacterial strains and from 24.0 ± 0.00 to 26.0 ± 0.00 mm against fungal strains. The oil also demonstrated 43% nematode mortality at 1 μL/mL after 96 h and 80% egg-hatching inhibition at the same concentration after 24 h. Spectroscopic analysis confirmed the isolated major constituent as pinocarvone. The essential oil of E. strobilifera is rich in bioactive constituents, particularly pinocarvone, and exhibits promising antioxidant, antimicrobial, and nematicidal activities. These findings support its potential as a natural source of biologically active compounds for pharmaceutical and agricultural applications.