Polyphenolic and Biogenic Volatile Organic Compound Profiles of Endemic Metallophytes From the Thallium-Rich Allchar Mining Area.

The Allchar Mining Area (North Macedonia) is an extreme metalliferous environment enriched in Tl, As and Sb that supports diverse endemic metallophytes. This study investigates metabolic profiles in selected species through integrated analysis of polyphenols (HPLC/DAD/MSn) and biogenic volatile organic compounds (BVOCs, headspace GC-MS). A total of 78 polyphenols and 123 volatile compounds were identified. Knautia caroli-rechingeri and Centaurea leucomalla were dominated by caffeoylquinic acid derivatives, in which reached 405.40 mg/g dry herb in K. caroli-rechingeri. Thymus thracicus var. alsarensis showed a distinct profile rich in rosmarinic and salvianolic acids, whereas Tl-hyperaccumulating Viola species were characterized by flavone and flavonol glycosides together with a markedly reduced diversity of phenolic acids. BVOC profiles also differed markedly among species, including terpene-rich profiles in Thymus, aldehyde-dominated compositions in Knautia and Centaurea, and non-terpenoid-enriched profiles in Viola species. Multivariate analysis confirmed species-specific metabolic patterns and significant concordance between polyphenolic and BVOC profiles (Mantel ρ = 0.72 and p = 0.008), while no significant association with reported Tl accumulation was observed. Metabolomic and metal accumulation patterns highlight species-specific biochemical characteristics associated with life in metalliferous habitats.