The culture medium containing the degradation products after the incubation period were centrifuged and the supernatants were extracted thrice with equal volume of ethyl acetate and dried over anhydrous Na2SO4. The solvent was evaporated in a rotary evaporator (SUPERFIT, PBU-6). Gas chromatography (Thermo TRACE ULTRA GC) equipped with mass spectrometry (TSQ QUANTUM) detector was used in the analysis of ethyl acetate extract. Helium (99.999%) was used as the carrier gas with a flow rate of 1.5 ml min 1 in the split less mode. An aliquot of 1ml of the sample was injected into the column. The oven temperature was programmed from 40 C (isothermal for 2 min), with an increase of 12 C min 1, to 300 C ending with an isothermal at 300 C for 5 min. Both the injector and auxiliary temperatures were set at 275 C, respectively. Ion source temperature was maintained at
225 C. The mass spectrum of compounds in samples was obtained by electron ionization at 70 eV and the detector was operated in scan mode from 45–450m/z. The total running timewas 28.67 min. Identification was based on the molecular structure, molecular mass and calculated fragments. Interpretation on mass spectrum GC–MS was conducted using the database of NIST, Library. The spectrum of the unknown component was compared with the spectrum of the component stored in the NIST library.