Antimicrobial and antibiofilm activities of Inga cylindrica trypsin inhibitor.

Inga cylindrica, a tropical fruit tree of the Fabaceae family (subfamily Mimosoideae), is native to South America. The seeds from this family are an essential source of trypsin inhibitors, which display promising bioactivity for increasing host defense against pathogens. The aim of the present study was to characterize the antimicrobial and antibiofilm activities of the trypsin inhibitor extracted from I. cylindrica seeds, ICTI. ICTI demonstrated antifungal activity with a minimum inhibitory concentration (MIC) of 32.11 μmol.L-1, and a minimum fungicidal concentration (MFC) of 32.1 μmol.L-1, against Cryptococcus gattii, Candida albicans, Candida glabrata and Candida guilliermondii. Combining ICTI with Amphotericin B had a significant synergistic effect, reducing the concentration of the antibiotic by 75% for C. albicans and 94% for C. gatti. The significant increase (16 x) in activity observed with ergosterol (1.01 mol.L-1) for C. albicans and C. gatti, and the lack of activity against bacterial strains, suggests that ICTI interferes with the integrity of the fungal cell membrane. Treatment with ICTI at 10 x MIC resulted in a 51% reduction in biofilm formation and a 56% decrease in mature biofilm colonies for C. albicans. Finally, ICTI displayed no toxicity in the in vivo Galleria mellonella model. Given its antifungal and antibiofilm properties, ICTI could be a promising candidate for the development of new antimicrobial drug prototypes.