Library Subscription: Guest
Begell Digital Portal Begell Digital Library eBooks Journals References & Proceedings Research Collections
International Journal on Algae
SJR: 0.229 SNIP: 0.261 CiteScore™: 0.24

ISSN Print: 1521-9429
ISSN Online: 1940-4328

International Journal on Algae

DOI: 10.1615/InterJAlgae.v11.i4.70
pages 377-393

Chemical composition and bioactivity of some benthic algae from Karachi Coast of Pakistan

Laila Shahnaz
Centre of Excellence in Marine Biology, University of Karachi, Karachi-75270, Pakistan
M. Shameel
Department of Botany, University of Karachi, Karachi-75270, Pakistan

ABSTRACT

Fourteen commonly occurring species of marine benthic algae were collected from the coastal area near Karachi (Pakistan) during March 1996 to September 1997 and extracted in methanol. A variety of saturated and unsaturated fatty acids (FAs) were detected from the extracts and analyzed as methyl esters qualitatively as well as quantitatively by gas chromatographic (GLC & GC-MS) techniques. Some sterols have also been detected, isolated and purified, their structure elucidated chemically through standard spectroscopic methods (EIMS and 1H- & C13 NMR). Altogether 57 different FA including 21 saturated fatty acids (SFAs) and 36 unsaturated fatty acids (UFAs) containing 19 monounsaturated (MUFA), 8 diunsaturated (DUFA), 6 triunsaturated (TUFA) and 3 polyunsaturated (PUFA) as well as 2 sterols i.e. β-Sitosterol and cholesterol were found. The SFAs were found in larger amount (53-84%) than UFAs (16-47%). Only in Chaetomorpha antennina and Acanthophora spicifera the UFAs were present in larger quantity (74-84%) than SFAs (16-26%). Palmitic acid (C16:0) was the most commonly occurring FA followed by oleic acid (C18:1); myristoleic (C14:1), pentadecylic (C15:0), pentadecatrienoic (C15:3), margaric (C17:0), stearic (C18:0) and nonadecylic (C19:0) acids were commonly detected. Algal extracts were also investigated for a variety of antibacterial tests. A. spicifera appeared to be most active seaweed against most of tested Gram-positive as well as Gram-negative bacteria. Staphylococcus aureus was found to be affected most against seaweed extracts, as 11 of the investigated extracts displayed a positive activity against it and only two did not. Among Gram-negative species the most sensitive bacterium was Shigella flexnariae. Chaetomorpha antennina exhibited antifungal activity against nine out of 13 tested fungal species and appeared to be the most active seaweed in this aspect. Microsporum canis was the most sensitive fungal species, its growth was affected by eleven out of 13 tested seaweeds. Oscillatoria sancta, Caulerpa scalpelliformis and Dictyopteris australis displayed a significant phytotoxicity and Acanthophora spicifera showed a significant cytotoxicity.