The aim of this study was to investigate the growth-inhibiting efficacy of Drosera intermedia extracts (water, methanol and n-hexane) against four food spoilage yeasts and five filamentous fungi strains responsible for food deterioration and associated with mycotoxin production, in order to identify potential antimycotic agents.
The n-hexane extract showed a broad activity spectrum against all tested microorganisms, followed, in activity, by the methanol and water extracts. The major component of the n-hexane extract was purified using a solid-phase extraction column and identified as plumbagin. Results show that high-purity plumbagin can be produced from D. intermedia cultures following a simple and effective isolation procedure. A sample of purified plumbagin was tested against the same panel of microorganisms and high growth-inhibiting capacity was observed. Minimum inhibitory concentrations less than 2 µg mL(-1) were obtained against the filamentous fungi. In the case of the species Aspergillus fumigatus, A. niger and A. flavus, activities comparable to miconazole were obtained.
The results obtained provided evidence of the antimycotic activity of plumbagin, suggesting that D. intermedia could be the source of an interesting compound for the food industry as an alternative to preservatives.