Combination of Cinnamaldehyde/(1-cyclodextrin inclusion complex and L-phenylalanine effectively reduces the postharvest green mold in citrus fruit

The essential oil and (1-cyclodextrin inclusion complex was able to inhibit the growth of Penicillium digitatum, a damaging pathogen that causes green mold in citrus fruit. In this study, cinnamaldehyde-(1-cyclodextrin inclusion complex ((1-CDCA) for controlling citrus green mold was synthesized by the co-precipitation method. Characterization of (1-CDCA revealed that the aromatic ring skeleton of cinnamaldehyde (CA) was successfully embedded into the cavity of (1-CD to form the inclusion complex. (1-CDCA inhibited P. digitatum at a minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of 4.0 g/L. FT-IR spectroscopy analysis, calcofluor white staining, extracellular alkaline phosphatase (AKP) activity and propidium iodide (PI) staining of hyphae morphology showed that (1-CDCA may damage the cell ultrastructure and membrane permeability of P. digitatum. The study further demonstrated that hydrogen peroxide (H2O2), malondialdehyde (MDA), and reactive oxygen species (ROS) markedly accumulated in 1/2 MIC (1-CDCA treated hyphae. This implied that (1-CDCA inhibited growth of P. digitatum by the triggering oxidative stress, which may have caused cell death by altering cell membrane permeability. In addition, in vivo results showed that (1-CDCA alone or combined with L-phenylalanine (L-PHe) displayed a comparable level to that of prochloraz. Therefore, (1-CDCA combined with L-PHe can thus be used as an eco-friendly preservative for the control green mold in postharvest citrus fruit.