Phytochemical Profile and Antioxidant Properties of Invasive Plants Ailanthus altissima (Mill.) Swingle and Helianthus tuberosus L. in Istria Region, Croatia

Abstract

Invasive alien plant species, while ecologically and economically problematic, represent an underutilized source of bioactive phytochemicals with promising phytopharmaceutical applications. This study investigates the LC-DAD-MS phenolic profiles of 70% ethanol and 80% methanol leaf and flower extracts of Ailanthus altissima (Mill.) Swingle and Helianthus tuberosus L., collected in the Istria region of Croatia, alongside their antioxidant capacities using ABTS, DPPH, and FRAP assays. Both species exhibited high levels of flavonoids and phenolic acids, with consistently higher concentrations in leaf versus flower tissues and in ethanolic versus methanolic extracts. Strong correlations (r > 0.9) between total phenolics and antioxidant activity confirmed the functional significance of these compounds. With a targeted metabolomics approach, in A. altissima, 51 phenolics were identified in leaves and 47 in flowers, with ellagitannins predominating; vescalagin isomers reached 94 mg/g DW in leaves and 82 mg/g DW in flowers. H. tuberosus extracts contained 34 phenolics in leaves and 33 in flowers, with hydroxycinnamic acids and flavonols dominating; 5-caffeoylquinic acid was the principal compound (25 mg/g DW in leaves, 2 mg/g DW in flowers). The identified phytochemicals are known for their potent antioxidant, anti-inflammatory, anticancer, antimicrobial, and metabolic-regulating properties. Additionally, four leaf-specific compounds were identified in each species, indicating potential for targeted extraction. These findings advance the phytochemical characterization of invasive taxa and highlight their potential as sources of natural antioxidants for functional food and pharmaceutical development.

Keywords: Jerusalem artichoke; extracts; phenolics; phytochemical profile; tree of heaven.

Figure 1

The content of total phenolics (TP), total non-flavonoids (TNF), total flavonoids (TF), and antioxidant capacity (measured by ABTS [2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid)] radical cation assay, DPPH (2,2-diphenyl-2-picrylhydrazyl) free radical assay, and FRAP (ferric reducing antioxidant power) assay) ABTS, DPPH, and FRAP assays in (A) A. altissima and (B) H. tuberosus leaf and flower extracts in two solvents (70% ethanol and 80% methanol). Different letters (a–d) in the same section indicate significant differences between the measured values (two-way ANOVA, Tukey’s test, p ≤ 0.01). All results are given in Table S1.

Figure 2

Pearson’s correlation coefficients of total phenolics (TP), non-flavonoids (TNF), and flavonoids (TF) contents and antioxidant capacities determined by ABTS, DPPH, and FRAP assays. (A) Only significant correlations (p ≤ 0.01; Table S2) are shown. (B) Total (0.9 < r < 1.0) and very strong (0.75 < r < 0.9) correlations; (C) Strong (0.50 < r < 0.75) correlations; (D) Weak correlations (0.25 < r < 0.5).

Figure 3

The main phenolic groups obtained by the LC-DAD-MS method in the leaf (and flower ethanolic extracts of (A) Ailanthus altissima and (B) Helianthus tuberosus. The ratio of the circles’ sizes corresponds to the total concentration of individual phenolic groups (mg/g of dry weight (DW)). The circle border indicates statistically significant differences between concentrations of individual phenolic groups between the plant organs (one-way ANOVA and LSD test, p ≤ 0.01). A. altissima leaf extract; A. altissima flower extract; H. tuberosus leaf extract; H. tuberosus flower extract.

Figure 4

The structures of the main compounds found in leaf and flower extracts of A. altissima (PubChem; available online: https://pubchem.ncbi.nlm.nih.gov/ (accessed on 20 May 2025)).

Figure 5

The structures of four main compounds found in leaf and flower extracts of H. tuberosus (PubChem; available online: https://pubchem.ncbi.nlm.nih.gov/ (accessed on 20 May 2025)).

Figure 6

Principal component analysis (PCA) of the individual metabolites in leaf (L) and flower (F) extracts in two solvents (EtOH, MeOH) and antioxidant capacity measured by three assays (ABTS, DPPH, FRAP) in (A,B) Ailanthus altissima and (C,D) Helianthus tuberosus. Numbers (1–60) are related to the individual identified phenolics, as depicted in the Table S6.