The Identification of Two Antibacterial Products of the Marine Planktonic Alga Isochrysis galbana

Abstract

SUMMARY The acetone-extractable antibacterial components of Zsochrysis galbana have been resolved by paper-chromatography and bioautography. Two pigmented products with similar antibacterial properties were obtained which were tentatively identified from their absorption spectra as chlorophyll a de- rivatives, probably pheophytin a and an atypical chlorophyllide a. METHODS Algal culture and extracts. Zsochrysis galbana Parke was grown in axenic culture and the algal material was harvested and dried as described by Antia & Kalmakoff Algal extracts were prepared by three methods. Method (a) involved sequential extractions with three solvent systems (acetone ; chloroform; chloroform + methanol (I + I, v/v)) at room temperature as described by Duff et al. (1966). Method (b) was similar to method (a) but with the extraction with each solvent system repeated twice before using the next solvent in the sequence. Method (c) involved sequential Soxhlet extractions (6 hr each) of algal cell powder (100 mg.) with the same solvent systems (25 ml. samples); each solvent extract was concentrated in vacuo to a 2 ml. equivalent of the extracts obtained by the other methods. The ratio of the weight of algal material to final volume of extract used in activity tests was taken as a measure of this equiva- lence. All extracts were stored at -30" and were protected from direct light at all times. (1965).