Abstract

A bioautography method was developed to determine the number of antifungal compounds in Terminalia species extracts. Acetone, hexane, dichloromethane and methanol leaf extracts of six Terminalia species (T. prunioides, T. brachystemma, T. sericea, T. gazensis, T. mollis and T. sambesiaca) were tested against five fungal animal pathogens (Candida albicans, Cryptococcus neoformans, Aspergillus fumigatus, Microsporum canis and Sporothrix schenkii).  The R_f values and relative activities of separated compounds were determined. Hexane and dichloromethane extracts had at least three times more antifungal compounds than the other extracts indicating the nonpolar character of the antifungal compounds. From the R_f values, the non-polar character of the antifungal compounds was confirmed indicating that the antifungal activity is not due to tannins. M. canis had the highest number, up to ten, of antifungal compounds. All Terminalia species contained a compound (R_f = 0.46 inbenzene/ethanol/ammonium hydroxide (90/10/1) active against all tested pathogens.  T. sericea and T. brachystemma were the most promising candidates for isolating antifungal compounds. The results demonstrate the value of bioautography in examining plant extracts with antifungal activity, selecting species for further study and dereplicating the isolation of compounds.

Key words: Combretaceae, Terminalia species, antifungal activity, bioautography, R_fvalue, dereplication.

Abbreviation

Abbreviations: AMB, Amphotericin B; DCM, dichloromethane; EMW, Ethyl acetate/methanol/water (40/5.4/4); CEF, chloroform/ethyl acetate/formic acid (5/4/1); BEA, benzene/eth-anol/ammonium hydroxide (90/10/1); INT, p-iodonitrotetrazolium violet; C.a, Candida albicans; C.n, Cryptococcus neoformans; M.c, Microsporum canis; S.s, Sporothrix schenckii; A.f, Asper-gillus fumigatus.