RESUMO
Terric acid,an antifungal metabolites produced by a marine mold Aspergillus flavis No. 179, was isolated and purified. The effects of terric acid at different concertrations on the growth and cellular morphology of C. albicans AS2, 538 were studied by the method of liquid dilution. The substance inhibits the growth of C. albicans AS2,538 obviously at low concentration and has fungicidal action at high concentration. The minimum inhibiting concentrations (MIC) and minimum lethal concentrations (MLC) on C. albicans AS2,538 were 6.25 microg/mL and 50 microg/mL, respectively. At Sub-MIC (3.13 microg/mL), terric acid inhibited the formation of pseudo-hyphal of C. albicans AS2, 538 and caused cell morphological change. After addition of terric acid to the medium to final concentration of 50 microg/mL, cell morphology of C. albicans AS2, 538 was irregular and some cells turned bigger and disrupted. The effects of terric acid on the synthesis of macromolecules, DNA, RNA or proteins of C. albicans AS2, 538 were estimated by measurement of incorporation of radioactive precursors, 14C-Thymidine, 3H-Uridine or 14 C-Valine, respectively. When C. albicans AS2, 538 was incubated for 4h in 5 g/mL terric acid medium, the incorporation of radioactive isoleucine and uridine decreased 47.8%, 70.7%, respectively, Compared with controls incubated in commonly medium. However, the incorporation of [3H]thymidine did not have significant change. This results indicated that terric acid inhibits the synthesis of protein and RNA but have no effect on DNA synthesis in a C. albicans AS2,538.
