07-08-2013, 01:05 PM
Production and partial characterisation of secondary metabolites from some fungal isolates
ABSTRACT
Endophytes are the organisms that reside within the living tissues of most plant species without inducing any pathogenic symptoms in the host. Various classes of natural products that have been discovered from endophytes include antitumor, antibacterial, antifungal and antiviral compounds. The isolated natural compounds might be indigenous to the host plant or a novel one. During the present investigation, a total of fifty fungal endophytes were isolated from different medicinal plants using surface sterilization method. From the fungal assemblage, only ten isolates were selected for further characterisation on the basis of their production of extracellular metabolites thereby changing the colour of growth media. Using classical taxonomical approaches the isolates were identified upto genus level. Four of them were identified as Aspergillus, three as Penicillium and rest three as Alternaria. For the production of secondary metabolites, fungal isolates were incubated at 28oC in PDB production media under shaking conditions. The filtrate so obtained was collected as extracellular metabolites source whereas intracellular metabolites were extracted with methanol from the biomass using Soxhlet apparatus. Both extracts and filtrates were screened for antibacterial and antifungal potential by well diffusion method. Antibacterial activity was shown by both filtrates as well as extracts of different fungal isolates but best results were obtained for fungal filtrates while antifungal activity was mainly shown by fungal extracts. For further characterisation, HPLC was performed using different steroidal standard compounds. Two culture extracts viz. LL-1 and LL-6 were found to be positive for the presence of Digoxin while another culture extract viz. FC-2 was found to be positive for the presence of Gingerol. Thus, the selected isolates can be exploited for the large scale production of industrially important compounds vizgingerol and digoxin.