Aspergillus carbonarius (Bainier) Thom. is an important pathogen and ochratoxin A (OTA) producer in grapes that
can be controlled by adopting sustainable approaches. Here we evaluate the application of natural plant extracts
as an alternative to synthetic fungicides to reduce OTA contamination and to prevent infection of grapes by two
isolates of A. carbonarius. In a preliminary screening, natural extracts of chestnut flower, cistus, eucalyptus,
fennel, and orange peel were evaluated for their antifungal and anti-mycotoxigenic efficiency in a grape-based
medium at concentrations of 10 and 20 mg/mL. Cistus and orange peel extracts demonstrated the best anti-
fungal activity at both concentrations. Although the eucalyptus extract demonstrated no significant effect on
Aspergillus vegetative growth, it significantly reduced OTA by up to 85.75 % at 10 mg/mL compared to the
control. Chestnut flower, cistus, eucalyptus, and orange peel extracts were then tested at the lowest concen-
tration (10 mg/mL) for their antifungal activity in artificially inoculated grape berries. The cistus and orange peel
extracts demonstrated the greatest antifungal activity and significantly reduced mold symptoms in grapes.
Moreover, all tested natural extracts were able to reduce OTA content in grape berries (17.7 ± 8.3 % - 82.3 ±
3.85 % inhibition), although not always significantly. Eucalyptus extract was particularly efficient, inhibiting
OTA production by both strains of A. carbonarius by up to >80 % with no effects on fungal growth. The use of
natural eucalyptus extract represents a feasible strategy to reduce OTA formation without disrupting fungal
growth, apparently maintaining the natural microbial balance, while cistus and orange peel extracts appear
promising as inhibitors of A. carbonarius mycelial growth. Our findings suggest that plant extracts may be useful
sources of bioactive chemicals for preventing A. carbonarius contamination and OTA production. Nonetheless, it
will be necessary to evaluate their effect on the organoleptic properties of the grapes.
This work was supported by the Foundation for Science and Tech-
nology (FCT, Portugal) #1 under Grant from national funds FCT/MCTES
(PIDDAC) to CIMO [number UIDB/00690/2020 and UIDP/00690/
2020] and SusTEC [number LA/P/0007/2020]; the European Regional
Development Fund (ERDF) through the Competitiveness and Interna-
tionalization Operational Program (CIOP) #2 under Grant dedicated to
the project “PreVineGrape - Development of a biofungicide to combat
grapevine diseases [number POCI-01-0247-FEDER-049695].
