Antimicrobial and Antidermatophytic Dihydroisocoumarins and Picolinic Acids Produced by Endophytic Fungus Fusarium napiforme of Faurea saligna Harv.

Winnie Cherotich Maritim (Egerton University)
Josphat Clement Matasyoh (Egerton University)

Biology, Medicine, & Natural Product Chemistry
Vol 15, No 2 (2026)

Fungal metabolites are reservoirs of bioactive molecules that impart therapeutic potential to medicinal plants. The fungus Fusarium napiforme was isolated from the internal tissues of the leaves of Faurea saligna. In this study, four dihydroisocoumarin: 7-butyl-15-enyl-6,8-dihydroxy-3(R)-pent-9,11-dienylisochroman-1-one (1), 7-butyl-15-enyl-6,8-dihydroxy-3(R)-pent-11-enylisochroman-1-one (2), 7-butyl-6,8-dihydroxy-3(R)-pent-11-enylisochroman-1-one (3), 7-butyl-6,8-dihydroxy-3(R)-pentylisochroman-1-one (4) and two piclinic acid derivatives: dehydrofusaric acid (5) and fusaric acid (6) were isolated from endophytic fungus F. napiforme. The elucidation of the chemical structures of the isolated compounds was performed by analysis based on spectroscopic analysis and comparison with reported literature. Compounds 1-6 were tested for antimicrobial and antidermatophytic activity against selected bacteria and fungi. All the compounds exhibited selective antibacterial activity against Staphylococcus aureus and Escherichia coli with a minimum inhibitory concentration (MIC) range of 62 – 175 µg/mL. Compounds 5 and 6 further exhibited antibacterial activity against Klepsiella pneumoniae with MIC value of 150 µg/mL. None of the compounds showed activity against Pseudomonas aeruginosa. Furthermore, all the compounds exhibited antifungal activity against Candida albicans with MIC values ranging from 48 µg/mL to 150 µg/mL. Compounds 1-4 further exhibited antidermatophytic activity against Trichophyton rubrum, Trichophyton benhamiae and Trichophyton interdigitale, with minimum inhibitory concentration (MIC) values ranging from 33.3 µg/mL to 66.6 µg/mL. Compounds 5 and 6 did not show any antidermatophytic activity against the highest concentration of 66.6 µg/mLused. Although, these compounds have been previously identified, this is the first instance of their reporting in endophytic fungi F. napiforme isolated from F, saligna. These results provide promising baseline information for the potential use of the compounds of this endophytic fungi as an antimicrobial and antidermatophytic for the control of diseases.