Highly branched C-25 isoprenoids in axenic cultures of Haslea ostrearia

The hydrocarbon compositions of axenic cultures of the diatom Haslea ostrea ria grown in the presence of penicillin, streptomycin and kanamycin were ex amined 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 t hree phases (2300-7000 fg cell(-1)). Of the ten HBI trienes to hexaenes rep orted previously from non-axenic cultures of H. ostrearia, four were presen t 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, no n-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 diff erences in HBI isomer distributions were observed among the three growth ph ases, For example, the newly identified, non-methylenic triene above, only occurred in the exponential growth phase. As a primary producer of these al kenes, several of which have demonstrated cytostatic activity, Haslea ostre aria, and perhaps related Haslea species, is clearly worthy of further stud y. (C) 1999 Elsevier Science Ltd. All rights reserved.