Background: Antimicrobial peptides (AMPs) are found in the defense system in virtually
all life forms, being present in many, if not all, plant species.
Objective: The present work evaluated the antimicrobial, enzymatic activity and mechanism of action
of the PEF2 fraction from Capsicum chinense Jack. seeds against phytopathogenic fungi.
Methods: Peptides were extracted from C. chinense seeds and subjected to reverse-phase chromatography
on an HPLC system using a C18 column coupled to a C8 guard column, then the obtained
PEF2 fraction was rechromatographed using a C2/C18 column. Two fractions, named PEF2A
and PEF2B, were obtained. The fractions were tested for antimicrobial activity on Colletotrichum
gloeosporioides, Colletotrichum lindemuthianum, Fusarium oxysporum and Fusarium
solani. Trypsin inhibition assays, reverse zymographic detection of protease inhibition and α-amylase
activity assays were also performed. The mechanism of action by which PEF2 acts on filamentous
fungi was studied through analysis of membrane permeability and production of reactive oxygen
species (ROS). Additionally, we investigated mitochondrial functionality and caspase activation
in fungal cells.
Results: It is possible to observe that PEF2 significantly inhibited trypsin activity and T. molitor
larval α-amylase activity. The PEF2 fraction was able to inhibit the growth of C. gloeosporioides,
C. lindemuthianum and F. oxysporum. PEF2A inhibited the growth of C. lindemuthianum (75%)
and F. solani (43%). PEF2B inhibited C. lindemuthianum growth (66%) and F. solani (94%). PEF2
permeabilized F. solani cell membranes and induced ROS in F. oxysporum and F. solani. PEF2
could dissipate mitochondrial membrane potential but did not cause the activation of caspases in
all studied fungi.
Conclusion: The results may contribute to the biotechnological application of these AMPs in the
control of pathogenic microorganisms in plants of agronomic importance.