Abstract

Analysis of bioactive natural compounds of algae such as cyanobacteria (Spirulina platensis; Nostoc linckia; Phormidium autumnale; Tolypothrix distorta and Microcystis aeruginosa) and green algae (Chlorella vulgaris and Dunaliella salina), and their activity against human pathogenic bacteria and yeast such as Salmonella suis ATCC 13076;Pseudomonas aeruginosa ATCC 27583; Escherichia coli ATCC 25922; Staphyllococcus aureus ATCC 25923; Bacillus subtilis ATCC 6633; Shigella sonnei ATCC 11060 andCandida albicans ATCC 10231 have been studied in Saudi Arabia. Extraction of algal metabolites was performed by using the mixture of three organic reagents, methanol:acetone:diethyl ether as 5:2:1 v/v, respectively. All metabolites of algae isolates had shown weak to strong antimicrobial activity toward one or more human pathogenic microorganisms. Almost all the algal extract showed strong activity against S. sonnei in agar well diffusion technique. Crude extract of cyanobacteria, T. distorta showed moderate to strong activity against S. aureus, B. subtilis and S. sonnei. Further, crude extract of all the algal metabolites have been analyzed using gas chromatography-mass spectrometry (GC-MS). Results indicated that the main component in the crude extracts of P. autumnaleis 1-Hexyl-2-Nitrocyclohexane (91.7%); C. vulgaris is 2-Butanol, 3-methyl-, (S)- (90.8%); S. platensis is Nitrocyclohexane-2-Hexyl-1 (92.1%); N. nostoc is Octadecanal (aldehyde) (86.8%); D. salina is 3-Methyl-2-(2-Oxopropyl) Furan (90.%); T. distorta is Boronic acid, Ethyl-, Dimethyl ester (83.9%) and lastly M. aeruginosa is (S)-(+)-1-Cyclohexylethylamine representing 91.9%, respectively. Further, in this study, the extracts of all the algal species especially T. distorta, P. automonate, C. vulgaris and D. salina have been found potential for the production of several compounds including biomedically important organic metabolites such as ethane,1,1-diethoxy-; butanal; heptanal and octanal. Further study for the purification of the potent compound will explain their usefulness in the pharmaceutical and biotechnological industry.

Key words: Cyanobacteria, green algae, algal extract, gas chromatography-mass spectrometry (GC-MS), antimicrobial activity, human pathogenic bacteria, biomedical properties.