Antifungal naphthalenes and related polyketides from the cranberry (Vaccinium macrocarpon) endophyte Protoventuria sp.

Ericaceous plants, including high-value fruit crops, harbor phylogenetically diverse fungal endophytes. A collection of ∼350 fungal endophytes from Canadian fruit-bearing plants was generated to investigate the taxonomic and secondary metabolite diversity of these poorly studied fungi. A putatively novel species of Protoventuria was isolated as an endophyte from a cranberry ( Vaccinium macrocarpon ) leaf in Central Ontario promoting an investigation of its secondary metabolites. From this fungus, two new naphthalenes, protoventurenes A and B ( 1 – 2 ), were characterized by LC-HRMS and NMR spectroscopy. Two additional structurally similar metabolites were also identified, the naphtalenone fragranone ( 3 ), previously reported from a shrub in Thailand, and the phenalenone derivative lamellicolic anhydride ( 4 ) originally from Verticillium lamellicola . Metabolites 1 – 4 inhibited the growth of the plant pathogen Botrytis cinerea with a 100-µg dose, and protoventurene B ( 2 ) inhibited Colletotrichum gloeosporioides at the same concentration. The investigation of ericaceous endophytes continues to reveal ecologically unique fungi and their new secondary metabolites. • A putatively novel Protoventuria sp. was collected as an endophyte of cranberry in Ontario, Canada. • Two new naphthalene natural products, protoventurenes A and B were isolated and characterized. • The naphtalenone fragranone and the phenalenone derivative lamellicolic anhydride were also characterized. • All metabolites inhibited the growth of the plant pathogen Botrytis cinerea . • Protoventurene B also inhibited the growth of Colletotrichum gloeosporioides .