Application of a selective method in the search for new bioactive natural products from fungi

Fungi are prolific sources of structurally novel and biologically active compounds. Over the past decades terrestrial fungi have been a major source of bioactive metabolites but often these have been obtained from easily accessible and culturable organisms while the apparently, rare and non-culturable groups remain an untapped resource [1]. While the need for new bioactive compounds is increasing, the yield of potentially useful new bioactive natural products from microbial sources is declining [2]. Part of this problem stems from the repeated discovery of known compounds due to the heavy reliance on soil actinomycetes and common soil fungi as their source.

A study was made using a range of phenol concentrations as a selective method for the isolation of ascomycetes from New Zealand soils. A total of 407 isolates were obtained. Culture extracts of a number of these isolates showed significant activity against the P388 murine leukaemia cell line, Bacillus subtilis and Candida albicans. Of these active extracts, one from Pseudeurotiom zonatum exhibited P388 activity with IC₅₀ value of 1,035ng/mL and two new cytochalasins were isolated.

This, isolation strategy for the characterisation and exploitation of the less readily culturable organisms would enhance the potential for the discovery of novel biotypes and new bioactive compounds.

Acknowledgements: Royal Thai Government, Ms. Gill Ellis, Mr. Craig Galilee Mr. Nic Cummings, Mr. Neil Andrews.

References: 1. Larsen, T. O. et al (2005) Nat. Prod. Rep. 22: 672–695. 2. Peric-Concha, N., Long, P.F. (2003) DDT 8:1078–1084.