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Biomedical potential of marine cyanobacteria
Author
Talbot, Christopher David
Supervisor
Tan, Lik Tong
Abstract
The tropical marine environment has proven to be a rich source of secondary metabolites. Approximately half of all newly discovered marine natural products exhibit bioactivity. A number of these natural products, or their derivatives, are currently in clinical trials, mainly in the treatment of cancer.
The majority of marine drug leads have been obtained from soft invertebrates that are found in tropical seas and are frequently members of coral reef communities. However, recent research is demonstrating that the ultimate source of some of these metabolites is cyanobacteria. These observations suggest that marine cyanobacteria from Singapore’s waters could be usefully screened for bioactive extracts.
Samples of the cyanobacterium Lyngbya sp. (TLT/SJ/003) were collected from a fish tank located at the Tropical Marine Science Institute on St. John’s Island. A methanol extract was obtained; the crude extract was then separated into organic and aqueous phases using liquid-liquid partitioning. The brine shrimp lethality assay was performed to assess the toxic activity of the organic phase. The crude extract exhibited biological
activity down to a concentration of 100 ppm.
Further fractionation was performed on the organic extract using gravity column chromatography. The brine shrimp bioassay was repeated on the fractions and bioactivity was detected in a number of them. All the fractions were subjected to one-dimensional thin layer chromatography and the four active fractions (4, 5, 7 and 8) were subjected to two-dimensional thin layer chromatography. Three of the four active fractions, namely, 4, 5 and 8 were subjected to 1H NMR analysis. Fraction 8 appeared to contain a natural product of a mixed polyketide/peptide nature, that is, a PKS/NRPS hybrid.
A sample of the cyanobacterium of the species Lyngbya majuscula (TLT/PHB/002) was collected by hand at low tide from the beach of Pulau Hantu. It was subjected to the same extraction and separation process, but initial fractionation was carried out using flash chromatography.
Samples from fractions 5 and 6 from the cyanobacterium sample (TLT/PHB/002) were subjected to 1H NMR analysis with the spectra suggesting the possible presence of a mixture of peptide-based molecules.
The majority of marine drug leads have been obtained from soft invertebrates that are found in tropical seas and are frequently members of coral reef communities. However, recent research is demonstrating that the ultimate source of some of these metabolites is cyanobacteria. These observations suggest that marine cyanobacteria from Singapore’s waters could be usefully screened for bioactive extracts.
Samples of the cyanobacterium Lyngbya sp. (TLT/SJ/003) were collected from a fish tank located at the Tropical Marine Science Institute on St. John’s Island. A methanol extract was obtained; the crude extract was then separated into organic and aqueous phases using liquid-liquid partitioning. The brine shrimp lethality assay was performed to assess the toxic activity of the organic phase. The crude extract exhibited biological
activity down to a concentration of 100 ppm.
Further fractionation was performed on the organic extract using gravity column chromatography. The brine shrimp bioassay was repeated on the fractions and bioactivity was detected in a number of them. All the fractions were subjected to one-dimensional thin layer chromatography and the four active fractions (4, 5, 7 and 8) were subjected to two-dimensional thin layer chromatography. Three of the four active fractions, namely, 4, 5 and 8 were subjected to 1H NMR analysis. Fraction 8 appeared to contain a natural product of a mixed polyketide/peptide nature, that is, a PKS/NRPS hybrid.
A sample of the cyanobacterium of the species Lyngbya majuscula (TLT/PHB/002) was collected by hand at low tide from the beach of Pulau Hantu. It was subjected to the same extraction and separation process, but initial fractionation was carried out using flash chromatography.
Samples from fractions 5 and 6 from the cyanobacterium sample (TLT/PHB/002) were subjected to 1H NMR analysis with the spectra suggesting the possible presence of a mixture of peptide-based molecules.
Date Issued
2006
Call Number
RS160.7 Tal
Date Submitted
2006