Antifungal properties of a sulfated polysaccharide-rich extract from Gracilaria coronopifolia and its application in controlling postharvest fungal decay in tomato.

Postharvest fungal diseases significantly reduce the quality and shelf life of produce, leading to major economic losses. This study evaluated the antifungal potential of an extract of fresh Gracilaria coronopifolia (GCE), a red seaweed rich in sulfated polysaccharides, against postharvest fungal pathogens. Chemical analysis revealed that the extract contained 66.07 ± 1.98% total sugar, an anhydrogalactose-to-galactose ratio of 1:1.84, 5.90 ± 0.05% sulfate content, a degree of sulfation of 0.37, and a molecular weight of 25.094 kDa. GCE exhibited concentration- and species-dependent antifungal activity by inhibiting biofilm formation, spore formation, spore germination, fungal biomass production and mycelial growth. Scanning electron microscopy (SEM) analysis revealed swelling and lysis of the fungal hyphae. Compared to no treatment, GCE treatment inhibited lesion diameter growth and maintained total phenolic content in in vivo pathogen-inoculated tomatoes during refrigerated storage, delaying decay. These results highlight the potential of G. coronopifolia extract as a natural and sustainable antifungal agent for postharvest disease management. Its application could support the development of eco-friendly strategies to mitigate fungal contamination and reduce reliance on synthetic fungicides during the postharvest handling.