Otospermum glabrum extracts: antioxidant properties and bioactivity against fungal pathogens and Aphis fabae

The adoption of plant-based biopesticides as sustainable alternatives to synthetic chemicals in agricultural pest management has gained increasing attention due to their safety and ecological benefits. Many of these natural compounds demonstrate potent antifungal activity, mitigating foodborne fungal contamination and associated mycotoxins. This study evaluated the antioxidant, antifungal, and aphicidal potential of Otospermum glabrum (Asteraceae) extracts derived from its aerial parts. Three extracts −ethyl acetate, methanolic, and aqueous− were assessed for total polyphenolic and flavonoid contents, antioxidant activity (DPPH radical scavenging, β-carotene bleaching, and total antioxidant capacity), antifungal effects against six post-harvest and crop fungal pathogens, and aphicidal activity against the black bean aphid (Aphis fabae Scop.). The ethyl acetate extract (EaE) exhibited the highest polyphenols (57.60 ± 0.17 μg GAE/mg) and flavonoids (49.46 ± 0.66 μg QE/mg), while the methanolic extract (ME) demonstrated the strongest DPPH scavenging activity (IC₅₀ = 56.05 ± 0.03 µg/ml) and β-carotene bleaching inhibition, comparable to BHT. The aqueous and ethyl acetate extracts showed the highest total antioxidant capacity (252.60 ± 0.20 and 249.10 ± 0.81 µg AAE/mg, respectively). Antifungal assays revealed that ethyl acetate and methanolic extracts were the most effective, with inhibition percentages (IP) exceeding 65% against all tested fungi. Additionally, the methanolic extract at 30% concentration induced 100% mortality in A. fabae after 72 h and exhibited significant repellency (48.98 ± 8.76%). These findings highlight O. glabrum as a promising source of natural biopesticides for integrated pest management.