The prospects of fungal endophytes of Nigerian rainforest medicinal plant origin as sources of novel anticancer drug molecules

The focus of drug discovery is currently shifting more in favour of plant derived microorganisms such as endophytic fungi [1 – 2], which have been found ubiquitous in their host plants. Nigerian medicinal plants, which hitherto have been poorly investigated, could hold enormous potentials as sources of novel fungi endophytes of medicinal importance. Our investigation of 10 medicinal plant species collected from the rainforest zone in Nigeria led to the isolation of 40 pure strains of fungi endophytes. The crude metabolites of these fungi endophytes were screened for cytotoxic activity against mouse lymphoma cell line (L5178Y) and for antimicrobial activity against strains of Gram positive and Gram negative bacteria as well as on some fungal strains. Further chemical investigation of two of the most promising fungi strains Corynespora cassiicola isolated from Gongronema latifolium leaves and Xylaria spp isolated from Psidium guajava leaves yielded 19 biomolecules. These included the new corynesidone D, corynether B and corynether lactone A from Corynespora cassiicola and the new (E) -methyl 3-(4-(3-oxocyclobutyl)phenyl) acrylate, 5,6-dihydro-7-oxo-19, 20- α-epoxycytochalasin C, 18-desoxy-19, 20- α-epoxycytochalasin C and 18-desoxycytochalasin C from Xylaria spp. These compounds are currently being investigated for their cytotoxicity against some selected human cancer cell lines and their ability to modulate the chaperoning activity of the Hsp90 chaperoning machine in vitro. To the best of our knowledge, this is the first report on the isolation of endophytes from these plant species and the results so far are quite fascinating.

References:

[1] Debbab, A.; Aly, A. H.; Proksch, P. Fungal Divers. 2012; 57, 45 – 83.

[2] Kusari, S and Spiteller M. Nat. Prod. Rep. 2011, 28, 1203 – 1207.