Chemical investigations of the cytotoxic extract of the marine-derived fungus Curvularia sp. (strain no. 768), isolated from the red alga Acanthophora spicifera, yielded the novel macrolide apralactone A (1), as well as the antipodes of curvularin macrolides 2–7. Compound 8, a dimeric curvularin was recognised as an artefact. The structures of 1–8 were elucidated by interpretation of their spectroscopic data (1D and 2D NMR, CD, MS, UV and IR). Apralactone A (1) is a 14-membered phenyl acetic acid macrolactone, and the first such compound with a 4-chromanone substructure. Compounds 1, 2, 4, 5 and 6 were found to be cytotoxic towards human tumor cell lines with mean IC50 values in the range of 1.25 to 30.06 µM.

Investigation of the secondary metabolites of the marine-derived fungus Curvularia sp. yielded four new 10-membered lactones (1-4), along with the known modiolide A (5). The structures of 1-4 were characterized on the basis of spectroscopic and MS data and resemble known 10-membered lactones, but feature modified oxidation patterns around their macrocycles.

A new cytotoxic bastadin, bastadin 24 ( 1), and the previously reported bastadins 4, 5, 6, 7, 12, 13, and 21 ( 2- 8) were isolated from a polar extract of the Australian marine sponge Ianthella quadrangulata. The planar structure of bastadin 24 ( 1) was elucidated as the 25-hydroxy derivative of bastadin 6 ( 4) by employing spectroscopic techniques (NMR, MS, UV, and IR). All isolated bastadins were evaluated for their cytotoxicity toward a panel of 36 human tumor cell lines and were found to be moderately cytotoxic. Bastadin 24 ( 1) exhibited selective cytotoxic activity toward five of the 36 investigated tumor cell lines. Bastadins 7 ( 5) and 12 ( 6) significantly inhibited the serum + hEGF-induced (human epithelial growth factor) tubular formation of human umbilical vein endothelial cells (HUVEC) at a concentration of 1 mug/mL.

Natural products play an important role in the development of anticancer drugs. To date, predominantly metabolites from plants and bacteria served as lead structures for anticancer agents. Fungal metabolites and derivatives thereof are much less investigated for their potential in cancer therapy. There are, however, some promising candidates derived from fungi in clinical phases I and II studies. This review gives an overview on the role of natural products in cancer therapy and summarises some of the latest results of our group in this area.