Pre-harvest UV irradiation differentially modulates terpenoids and esters in tarragon (Artemisia dracunculus L.) for enhanced essential oil quality.

Tarragon (Artemisia dracunculus L.) is an aromatic herb of industrial significance, valued for its essential oil composition that determines its applications in the flavor, fragrance, and cosmetic industries. Although ultraviolet (UV) radiation is known to modulate plant secondary metabolism, its potential as a pre-harvest strategy to enhance the volatile profile of tarragon for industrial applications remains unexplored. The present study employed headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) to characterize the treatment-specific effects of supplemental ultraviolet A (UV-A), ultraviolet B (UV-B), and their combination (UV-A+UV-B) on the volatile metabolome of tarragon. Through HS-GC-IMS and HS-SPME-GC-MS analyses, 57 and 169 volatile organic compounds (VOCs) were identified, respectively. Across all irradiation treatments, terpenoids constituted the predominant chemical class, accounting for 40-52% of the total volatile profile. Orthogonal partial least squares discriminant analysis (OPLS-DA) yielded excellent discrimination among the four experimental groups (Q² > 0.95). Based on variable importance in projection (VIP) scores exceeding 1.0, a total of 21 differential VOCs were selected from the HS-GC-IMS dataset and 101 from the HS-SPME-GC-MS dataset, which collectively enabled clear separation of the four UV exposure regimens. UV-B irradiation specifically enhanced key industrial-relevant terpenoids (γ-terpinene, β-ocimene) and ketones, while combined UV-A+UV-B treatment synergistically increased ester levels, enriching compounds associated with fruity and floral notes desirable in perfumery applications. The complementary analytical platforms provided near-complete coverage of the tarragon volatilome, overcoming technique-specific limitations. These findings demonstrate that targeted pre-harvest UV irradiation differentially regulates terpenoids and esters, offering a practical strategy to improve the industrial quality of tarragon essential oil and providing a scientific basis for optimizing cultivation practices for aromatic crops.