Highly branched C25 isoprenoids in axenic cultures of Haslea ostrearia

The hydrocarbon compositions of axenic cultures of the diatom Haslea ostrearia grown in the presence of penicillin, streptomycin and kanamycin were examined at lag, exponential and stationary growth phases. The production of highly branched isoprenoid (HBI) C-25 trienes to pentaenes with the 2,6,10,14-tetramethyl-7-(3-methylpentyl) carbon skeleton was demonstrated at all three phases (2300-7000 fg cell(-1)). Of the ten HBI trienes to hexaenes reported previously from non-axenic cultures of H. ostrearia, four were present in the axenic samples. In addition, two novel trienes and a pentaene were found. The most abundant of the new trienes was isolated from a larger, non-axenic batch culture and identified from C-13- and H-1-NMR data as 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)pentadec-5,9-diene. Interesting differences in HBI isomer distributions were observed among the three growth phases, For example, the newly identified, non-methylenic triene above, only occurred in the exponential growth phase. As a primary producer of these alkenes, several of which have demonstrated cytostatic activity, Haslea ostrearia, and perhaps related Haslea species, is clearly worthy of further study. (C) 1999 Elsevier Science Ltd. All rights reserved.