Fermentation-based extraction of polyphenolic bioactive compounds from Larrea tridentata using the fungal strain Trichoderma asperellum

Introduction: Postharvest fruit losses are substantial due to phytopathogenic fungal infections, which can lead to fruit decay and a reduction in quality and commercial value. Common culprits include fungi such as Alternaria, Aspergillus, and Botrytis, which result in significant economic losses in the fruit industry. To mitigate these losses, it is imperative to study the molecular and metabolic processes involved in fungal infections and to develop effective disease control strategies. Plants produce bioactive metabolites that are considered safe, effective, and ecologically beneficial and serve as botanical fungicides against phytopathogenic fungi.
Methods: Pulverized air-dried leaves and stems of Larrea tridentata were subjected to fermentative extraction processes involving the use of the filamentous fungus Trichoderma asperellum for 120 h in both the solid and liquid states. The extracts (1 %) were then analyzed in terms of their polyphenolic constituents using Folin–Ciocalteu reagent and HCl butanol, and they were further assayed in vitro against Fusarium oxysporum and Alternaria alternata using plate-poisoning methods. Their phytoconstituents were quantitatively screened using RP-HPLC-ESI-MS. The antioxidant potential of the extracts was also tested using the FRAP, ABTS, and DPPH assays.
Results: The findings indicated that the solid-state fermentation of L. tridentata leaf extract meant that at 72 h, it contained hydrolyzable tannins (3.16 mg/g). Conversely, the liquid-state L. tridentata leaf extract exhibited the highest level of condensed tannins (3.29 mg/g) at 120 h. The liquid-state L. tridentata leaf extract at 120 h inhibited the growth of A. alternata by 62.6%, whereas the liquid-state L. tridentata stem extract inhibited the growth of F. oxysporum by 56.7%. All the extracts displayed significant antioxidant potential in the ABTS, DPPH, and FRAP assays. Eight major polyphenolic compounds were identified: quercetin, luteolin, 3,4-DHPEA, elenolic acid, NDGA, 5-Heptadecylresorcinol, 3,7-Dimethylquercetin, and kaempferide.
Conclusion: The L. tridentata leaf extracts exhibited strong fungistatic effects against phytopathogenic fungi, demonstrating their potential as bioactive ingredients in biopesticide formulations.