Abstract:
Marine red algae of the genus Hypnea are globally recognised for their ecological and economic
significance. It is also renowned as a sustainable source of carrageenan, a sulphated
polysaccharide with extensive applications in the food, pharmaceutical, and cosmetic industries.
Accurate taxonomic identification of this species is crucial for optimising its utilisation
and ensuring consistency in bioactive compound extraction. In the present study, the taxonomic
identification of the collected Hypnea sp. was confirmed by comparison of the observed morphoanatomical
characteristics with established taxonomic literature and through biochemical
evidence, particularly the presence of carrageenan in the collected species. Observed morphological
traits included the morphology, texture, and color of the thallus; shape of the holdfast;
tip morphology; branching pattern; and thallus height. Anatomical characterisation focused
on the arrangement of cortical and medullary cells and reproductive structures such as cystocarps.
These features collectively confirmed the genus identity of the collected specimens.
Carrageenan extraction, which served as the biochemical confirmation of genus identity, was
conducted through hot NaOH treatment, aqueous re-dissolution, and ethanol precipitation. The
process yielded 17.8±0.4% carrageenan, which aligns with reported seasonal variations in yield
for Hypnea species (10 - 40%). The extracted carrageenan was characterised by Attenuated
Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and by analysing the
moisture content of the extract. The ATR-FTIR revealed distinct peaks at 928, 888, 847, and
767 cm-1, indicating the 3,6-anhydro-D-galactose, sulfate ester vibration, C–O–SO4 stretching
at the C4 position of galactose, and a general vibration band for sulfated polysaccharides,
respectively. These peaks closely match those of standard kappa carrageenan. Additionally,
the moisture content of the dried carrageenan was determined to be 9.3±0.2%, consistent with
previously reported values. The integration of morphological, anatomical, and biochemical
evidence validates the taxonomic identity and biochemical potential of the specimens and underscores
the biotechnological potential of Hypnea sp. for marine bioprospecting and natural
product development.
