Journal of Applied Phycology 6: 443-446, 1994. 443 ( 1994 Kluwer Academic Publishers. Printed in Belgium. Isethionate in certain red algae P. B. Holst 1 , S. E. Nielsen 1 , U. Anthoni', K. S. Bisht 2 , C. Christophersenl*, S. Gupta 2 , V. S. Parmar 2 , P. H. Nielsen', D. B. Sahoo 2 & A. Singh 2 I Marine Chemistry Section, The H. C. Orsted Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark 2 Department of Chemistry, University of Delhi, Delhi - 110007, India (* Authorfor correspondence) Received 9 August 1994; accepted 12 August 1994 Key words: Rhodophyta, Gigartinales, Hypnea musciformis, isethonic acid Abstract Isethionic acid (2-hydroxyethanesulfonic acid) was isolated as salts from a methanolic extract of Hypnea musci- formis collected in the Indian Ocean and identified by comparison (nuclear magnetic resonance, infrared and mass spectrometry) with an authentic sample. The compound has not previously been reported from plants. Investigations of 13 other species of red algae showed that only some samples of species of the families Gigartinaceae, Hypnaceae and Solieriaceae (all of order Gigartinales) contained isethionates. Introduction During routine screening of marine specimens, a methanolic fraction from a red algae, Hypnea mus- ciformis, from the Indian Ocean was found to contain surprisingly high amounts (8.9% of the aqueous extract) of salts of isethionic acid (2- hydroxyethanesulfonic acid). Isethionate has previous- ly been identified as a the major anion (200 mol g-l) of the squid axoplasm probably contributing to the bio- electric behaviour of the squid axon as an important calcium binding ion (Hoskin, 1971; Christoffersen & Skibsted, 1975). Smaller amounts have been found in other squid tissues and in three cephalopods, a gastro- pod and a bivalve and isethionate is probably common among cephalopods (Hoskin & Brande, 1973). It is a normal component of the tissue of higher animals in micro- to millimolar concentrations probably formed from taurine by gut microorganisms (Ikiheimo et al., 1982; Kumpulainen et al., 1982). Isolated occurrences include the orb web of garden spiders contributing to the extension of the fibres (Vollrath et al., 1990) and the brain of the honey-bee (Jacobsen, 1967). Further- more it may be formed in cultures of Aspergillus niger (Kondo et al., 1977). The observation of isethionate in H. musciformis therefore led us to investigate fourteen red algal species in order to determine the taxonomic distribution of isethionic acid. Materials and methods Plant material Details of the origin of the specimens investigat- ed are summarised in Table 1. Hypnea musciforrnis (Wulf.) Lamour was collected from Okha Port between 22 28'N and 69 05'E on North Gujarat Coast, India bordered by the Arabian Sea during the last week of January 1992 and identified by Prof. M. R. Vija- yaraghavan, Dept Botany, Univ. Delhi. Extraction and isolation Dried Hypnea musciformis (200 g) was extracted sev- eral times with boiling methanol, the extracts com- bined and taken to dryness in vacuo to give 4 g sol- id extract. This was partitioned between ethyl acetate and water (1:1) to separate lipophilic from hydrophilic constituents. The water soluble fraction (734 mg after