Study on anti- yeast activity of active fraction obtained from Urena lobata L.leaves

In the present study,the leaves of Urena lobata L.were used as raw material.U.lobata leaves were treated with n-hexane( 1∶20 g / m L) to remove the low polarity components,and then extracted with methanol( 1∶25 g / m L).By bioassay guide of anti- yeast activity,the 100% methanol elution was obtained as the main active fraction from the crude extract through macroporous resin Diaion HP-20 column chromatography.The antimicrobial activity of all strains was investigated by Oxford cup method. The micro- dilution method was used to calculate Minimum inhibitory concentrations( MICs) and Minimum fungicidal concentration( MFCs).Meanwhile,the effects of the active fraction on yeast growth cycle and cell morphology were observed according to killing curves and transmission electron microscope( TEM),respectively.At a concentration of 10 mg / m L,the active fraction exhibited 9.20 mm of inhibitory zone diameter against Aspergillus niger and 15.10 mm of inhibitory zone diameter against Saccharomyces cerevisiae. However,the anti- yeast activity was different from different kind of Saccharomyces cerevisiae with inhibitory zone diameters ranging from 14 to 17 mm.The MICs and MFCs of the active fraction were detected to be in ranges of 29.30~58.60 μg / m L and 117.20~468.80 μg / m L,respectively.The killing curves indicated that the anti- yeast activity mainly occured at the log phase.The TEM results showed that the active fraction killed yeast cells through destructing yeast cell wall and membrane,and resulting in the leakage of cytoplasm.