Coumaric acid analogues inhibit growth and melanin biosynthesis in Cryptococcus neoformans and potentialize amphotericin B antifungal activity

• Published in: European journal of pharmaceutical sciences 2020-10, Vol.153, p.105473-105473, Article 105473
• Main Authors: Oliveira, Lidiane, Ferrarini, Márcio, dos Santos, Alexandre Paes, Varela, Marina Themoteo, Corrêa, Isabela Teresa Santos, Tempone, André Gustavo, Melhem, Marcia S.C., Vallim, Marcelo A., Fernandes, João Paulo S., Pascon, Renata C.
• Format: Article
• Language: English
• Subjects: Amphotericin B; Antifungal agent; Coumaric acid analogues; Cryptococcosis; Melanin; Tyrosinase inhibitor
• ISSN: 0928-0987; 1879-0720
• DOI: 10.1016/j.ejps.2020.105473

•Novel coumaric acid analogues with fungal tyrosinase inhibitory activity are described.•These compounds also cause growth arrest and melanization inhibition in the opportunistic yeast C. neoformans.•The coumaric analogues described in this article potentialize amphotericin B fungicidal activity in C. neoformans.•C. neoformans may be useful as model system to screen for novel and more potent antimelanogenic activity. Fungal infections are on the rise, since the imunocompromised population is increasing due to AIDS/HIV, organ transplant and chemotherapy. Many environmental and pathogenic fungi are able to accomplish melanin biosynthesis as a virulence factor to promote host invasion. Melanized cells are more resistant to radiation, oxidative and osmotic stresses; also melanin confers an advantage in vivo, since melanized cells are more resistant to phagocytic engulfment and oxidative stress caused by the host defense cells and by some antifungal drugs, such as fluconazole (FCZ) and amphotericin B (AmB). Brown, red or black melanin pigments can be produced by the polyketide pathway (DHN-melanin) or from dihydroxyphenols, such as L-DOPA (L-3,4-dihydroxyphenylalanine) and L-tyrosine by polyphenoloxidases. Among several pathogenic fungi, Cryptococcus neoformans is a melanized yeast that causes pneumonia and meningoencephalitis in immunocompromised patients. The knockout of the laccase genes or other interruptions on melanin biosynthetic pathway generates cryptococcal strains with attenuated virulence in an animal model. In this study 16 analogues of coumaric and cinnamic acid were evaluated as possible tyrosinase inhibitors. We have identified some valuable inhibitors of C. neoformans growth and melanin biosynthesis disruption agents. The results showed that coumaric acid derivatives (1a-c), the ketones (3a-b) and 2-allylphenol (7c) are significant inhibitors of tyrosinase and melanization of the fungus. Two analogues (1b and 3b) were selected as promising antimelanogenic agents to be combined with AmB, showing to promote 16-fold reduction in the AmB fungicidal concentration with no appreciable cytotoxicity to mammalian cells. The data suggest that inhibition of the melanin biosynthesis by these compounds may increase the susceptibility of the cells to the oxidative stress generated by AmB. In summary, our data show that C. neoformans can be a suitable model system to test novel inhibitors that target melanin biosynthesis, and novel compounds for adjunct therap