Antifungal application of pine derived products for sustainable forest resource exploitation

In order to investigate the effect of thiophene heterocyclic group on antifungal activity, two series of rosin-based derivatives were designed and synthesized. The antifungal effects on Thanatephorus cucumeris, Botrytis cinerea, Valsa mali, and Sclerotinia sclerotiorum were assessed. The dehydroabietyl acyl-thiourea compounds containing a thiophene heterocyclic group had mild to strong antifungal effects on V. mali. Among these molecules, compound 5e showed more excellent effects on V. mali with concentration for 50% of maximal effect (EC50) of 0.184 mg/L, which was lower than carbendazim. Compound 5e was also efficient against V. mali in vivo, with remarkably altered morphology, elevated cell membrane permeability, and decreased pectinase activity compared with the control group. Next, four parameters linking structural features and antifungal effects on V. mali were examined, including max net atomic charge for a S atom (qSmax), energy gap between the highest occupied molecular orbit and the lowest unoccupied orbit in atomic units (HOMO-LUMO), the logarithm of molecular surface area (log MS), and dipole moment (DM), and used for building a quantitative structure-activity relationship (QSAR) model (R2 = 0.9660). Preliminary structure-activity relationship (SAR) and QSAR evaluations indicated electronic and steric effects, and energy differences of different compounds had remarkable influences on antifungal properties. These results provided new insights into the mechanisms behind the antifungal properties of rosin-based with thiophene heterocyclic group derivatives. Guided by this study, some potential substitutes can be currently used in fungicides and some new antifungals can be led for developing.