Elucidating the dual agro-biochemical roles of Dittrichia viscosa methanolic and ethanolic extracts: Biostimulant-driven germination, crop enhancement, and antioxidant synergy

ABSTRACT Dittrichia viscosa (L.) Greuter, a Mediterranean ruderal species, exhibits dual agro-biochemical roles as both a biostimulant and allelopathic agent. This study evaluated methanolic and ethanolic extracts for phytochemical content, antioxidant activity, and biostimulant efficacy on Vicia faba and Citrus clementina. Methanolic extracts contained significantly higher polyphenols (215.8 ± 22.7 mg GAE/g), flavonoids (112.0 ± 19.0 mg QE/g), and tannins (52.9 ± 2.0 mg/g) compared to ethanolic extracts (110.9 ± 17.6 mg GAE/g, 16.0 ± 3.1 mg QE/g, 11.2 ± 1.0 mg/g). Despite this, ethanolic extracts exhibited stronger antioxidant scavenging, with lower IC50 values in DPPH (0.49 ± 0.14 mg/mL) and ABTS (0.33 ± 0.22 mg/mL) assays than methanolic extracts (0.72 ± 0.05 and 0.93 ± 0.12 mg/mL, respectively). Hydroponic root assays demonstrated methanolic extracts enhanced Vicia faba root length significantly at 0.05 mg/mL (5.85 ± 1.32 cm) and Citrus clementina roots at 0.05 mg/mL (2.73 ± 0.38 cm), outperforming ethanolic extracts which showed inhibitory effects at higher doses. In vivo greenhouse experiments confirmed methanolic extract treatments increased Vicia faba seed number and weight significantly (p < 0.001), alongside larger seed sacs and stem sizes compared to controls and ethanol treatments. These findings validate D. viscosa as a promising natural bio-stimulant with antioxidant synergy for sustainable agriculture.