The Bioactivity and Natural Products of Scottish Seaweeds
Seaweed has traditionally been used in Scotland and other countries both as food and for medicinal purposes, which has led to seaweed being investigated for their natural product content. Despite over 30 years of research, the majority of species found in Scotland have yet to have their chemistry examined. Extracts of seaweed were tested for antimicrobial activity against marine bacteria. Extracts of Palmaria palmata, Ulva linza, Chondrus crispus and Pelvetia canaliculata showed no detectable activity, while ethyl acetate extracts of Fucus serratus, Halidrys siliquosa, Osmundea pinnatifida and Polysiphonia fucoides showed activity against at least six of the seven strains. Extracts were screened for radical scavenging activity against ABTS, DPPH and superoxide radicals. At least one extract from each brown seaweed showed radical scavenging of at least 80 % towards ABTS·+ with an ethyl acetate extract of P. fucoides and H. siliquosa quenching DPPH· by at least 90%. Radical scavenging activity appears to be dependent total phenolic content of extract. Extracts were subjected to a series of assays relevant to human health. Ethyl acetate extracts showed high antiparasitic activity against Trypanosoma brucei with a P. fucoides extract showing antibacterial activity toward Staphylococcus aureus. Extracts of H. siliquosa and F. serratus showed cytotoxicity to Hela cells with extracts of H. siliquosa showing cytotoxicity to LN CAP AS and PC 3 cell lines. An extract of H. siliquosa underwent chromatography and by applying assay guided fractionation, several active fractions were identified. These were analysed using NMR and LC/MS and four compounds identified: (2E. 6E. 14E)-l-(l’-hydroxy-4’-methoxy-6’- methyl-phenyl)-5, 13-dihydroxy-12-one-3, 7, 11, 15-tetramethylhexadeca-2, 6, 14-triene, a known antibacterial compound, previously identified in H. siliquosa; (2E, 6E, 10E, l4E)-1- (1’-hydroxy-4’-methoxy-6’-methyl phenyl)-5, 12 dihydroxy-3.7, 11, 15-tetramethyl hexadeca-2.6, 10, l4-tetraene, previously identified in Cystoseira elegans, and now in H. siliquosa; and two compounds that have not been reported before.
Seaweed, Algae, Natural Products, Bioactivity
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