java.lang.NoClassDefFoundError: org/apache/tools/ant/BuildException error

I am getting the above error when running this script in SOAPUI-5.2.0

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def ant = new AntBuilder()

mp=\'http://mp.com/api/schemas\'; //mp:JobDiagnosticBundleResponse[1]/mp:Filename[1]}' )
def SourceFileName = context.expand( '${JobDiagnosticBundle180#Response#declare namespace mp=\'http://mp.com/api/schemas\'; //mp:JobDiagnosticBundleResponse[1]/mp:Filename[1]}' )

log.info SourceFileName.toString()

def DestinationFileName = SourceFileName.toString()[0..-5]
ant.unzip(src:SourceFileName,
                dest:DestinationFileName,
                overwrite:"false")

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I have copied the following two files in the bin/ext and bin/lib folders

ant-launcher-1.9.6.jar

apache-ant-1.8.2.jar

Further, I guess the CLASSPATH is also correctly configured. See below

nadeemhassan:/ nadeemh$ pwd

/

nadeemhassan:/ nadeemh$ echo $ANT_HOME

/Users/nadeemh/Applications/apache-ant-1.9.6

nadeemhassan:/ nadeemh$

nadeemhassan:/ nadeemh$ echo $JAVA_HOME

/Library/Java/JavaVirtualMachines/jdk1.8.0_40.jdk/Contents/Home

Please advise....

Thanks in advance.