Preliminary biological screening of some marine algae collected from Karachi coasts of Arabian Sea

The antibacterial assay using the ethanol extracts of the studied algae sho wed significant activity against bacteria while the water and chloroform ex tracts wen found inactive. Most of the algae showed very significant activi ty against Corynebacterium diptheriae and Staphylococcus aureus: The result s of the antifungal assay showed that all the extracts i.e. Ethanol chlorof orm and water extracts an capable to inhibit the growth of human. animal an d plant pathogens. Most of the extracts showed inhibitory activity, however few of the extracts were found to promote the growth of certain fungi. The ethanol extracts of the most of the three classes of algae had antifungal activity against human pathogens. An interesting observation was made regar ding the ethanol, chloroform and water extracts of Iyengaria stellata, all of which were found active against animal pathogen Microsporum canis. From all the algae tested, the ethanol extract of Codium iyengarii showed very s ignificant antifungal activity against all types of pathogens. The brine sh rimp lethality bioassay showed that most of the ethanol, chloroform and wat er extracts wee active but the LD50 values of most of the extracts were hig her than 1000 mug/ml. The ethanol extracts of green algae did not show sign ificant results. The water extracts of the three classes of algae were acti ve at higher doses. The results of the Lemna bioassay showed that some of t he ethanol extracts of the algae inhibit while others help to promote the g rowth of Lemna aequinoctiatls welv. The water extracts of different alga we re found to promote the growth of the tested plant A very interesting resul t was observed from the ethanol extract of Sargassum teneriumum which gave 100% inhibition of the fronds at highest concentration i.e 500 ppm Among th e chloroform extracts the most active was the chloroform extract of green a lgae Codium iyengarii. This extract significantly inhibited the growth in a ll three concentrations. From all the algae tested for the phytotoxic activ ity, the extracts (ethanol, chloroform and water) of brown alga Iyengaria s tellata were found to inhibit the growth of the fronds while the extracts ( ethanol, chloroform and water) of the red alga Melanothamnus somalensis pro moted the growth of L. aequinoctiatls.