Extraction of antibacterial substances, galactofucoidan and alginate successively from the Gulf of Mannar brown seaweed <i style="mso-bidi-font-style:normal">Sargassum wightii</i> Greville ex J. Agardh

Abstract

In the present study, galactose dominated fucoidan was isolated through successive extraction method in alkaline, acid and neutral pH from the brown seaweed <i style="mso-bidi-font-style:normal">Sargassum wightii </i>Greville ex J. Agardh collected along the Gulf of Mannar (Pamban, India) during March 2011. In this study, crude extracts obtained in chloroform: methanol (1:1 v/v) and 85 % ethanol (at 23°C and 70°C) showed antibacterial activity against <i>Xanthomonas axonopodis </i>pv<i>. citri </i><span style="mso-bidi-font-style:italic">and <i style="mso-bidi-font-style: normal">X. oryzae </i>pv.<i style="mso-bidi-font-style:normal"> oryzae</i> which cause canker in citrus and blight of paddy, respectively. Low (<span style="mso-bidi-font-family:" times="" new="" roman""="" lang="EN-GB">< 3500 Da) and high molecular weight (<span style="mso-bidi-font-family:" times="" new="" roman""="" lang="EN-GB">> 3500 Da) fucoidans separated through DEAE cellulose 52 column were recorded same proportion of monosugars constituents dominating D-galactose over L-fucose. Spectroscopic studies (IR & NMR) of high molecular weight fucoidan (Fraction, A1H) with high sulphate showed higher anticoagulation activity than low molecular weight fucoidan under <i style="mso-bidi-font-style:normal">in vitro</i> APTT assay. This investigation concludes that successive extraction method yields galactofucoidan (3.62 %), alginate (11.2 %) and antibacterial substances (13.34 %) in the same biomass of brown seaweed <i style="mso-bidi-font-style:normal">S. wightii</i>.

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