Preliminary Biological Screening of Some Marine Algae Collected from Karachi Coasts of Arabian Sea

Abstract

The antibacterial assay using the ethanol extracts of the studied algae showed significant activity against bacteria while the water and chloroform extracts were found inactive. Most of the algae showed very significant activity against Corynebacterium diptheriae and Staphylococcus aureus: The results of the antifungal assay showed that all the extracts i.e. Ethanol, chloroform and water extracts are capable to inhibit the growth of human, animal and 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 regarding 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 significant antifungal activity against all types of pathogens. The brine shrimp lethality bioassay showed that most of the ethanol, chloroform and water extracts were active but the LD50 values of most of the extracts were higher than 1000 μg/ml. The ethanol extracts of green algae did not show significant results. The water extracts of the three classes of algae were active at higher doses. The results of the Lemna bioassay showed that some of the ethanol extracts of the algae inhibit while others help to promote the growth of Lemna aequinoctiatls welv. The water extracts of different alga were found to promote the growth of the tested plant A very interesting result was observed from the ethanol extract of Sargassum teneriumum which gave 100 % inhibition of the fronds at highest concentration i.e 500 ppm. Among the chloroform extracts the most active was the chloroform extract of green algae Codium iyengarii. This extract significantly inhibited the growth in all three concentrations. From all the algae tested for the phytotoxic activity, the extracts (ethanol, chloroform and water) of brown alga Iyengaria stellata were found to inhibit the growth of the fronds while the extracts (ethanol, chloroform and water) of the red alga Melanothamnus somalensis promoted the growth of L. aequinoctiatls. Show more