Pathogenic fungi in the biomedical and agricultural settings continue to develop resistance against current antifungal drugs (e.g., the annual one million human deaths and major crop losses due to fungal infections). The feijoa plant, Acca sellowiana, is classified in the family Myrtaceae, native to South America, and currently grown worldwide to produce feijoa fruit. Antifungal compounds have been isolated from feijoa; however, the diversity of these compounds is not known nor is the mechanism of action of any of these compounds. To explore the potential of agricultural waste products as a source of novel antifungal compounds, we obtained an unbiased GC-MS profile of 151 compounds from 16 commercial and experimental cultivars of feijoa peels. Bioactivity-guided multivariate partial least squares regression analyses distinguished 18 compounds that were significantly correlated to antifungal activity, of which seven had not previously been described from feijoa. Two novel cultivars were the most bioactive, and the compound 4-cyclopentene-1,3-dione, detected in these cultivars, was potently antifungal (IC50 = 1-2 μM) against human pathogenic Candida species. Haploinsufficiency and fluorescence microscopy analyses determined that the synthesis of chitin, a fungal-specific cell wall polysaccharide, was the target of 4-cyclopentene-1,3-dione. Structure-activity relationship analyses are in progress to further understand the antifungal activity of 4-cyclopentene-1,3-dione. Together, our results indicate that the agricultural waste product of feijoa peels is a natural source of potential high-value antifungal compounds that potently inhibits the growth of fungal pathogens.

Antifungal metabolite profiling of high value compounds in fruit peel waste

2019 Fall National Meeting

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