Some Physicochemical Characteristics of the Marennine-Like Pigment Synthesized by the Marine Diatom Haslea karadagensis (Bacillariophyta)

Marennine and marennine-like pigments produced by certain diatom species of the genus Haslea are unique water-soluble compounds with several valuable properties. The exact chemical structure of these pigments has not been fully elucidated, but data on the physical and chemical characteristics of marennines have been obtained primarily for H. ostrearia. Over the past 15 years, four additional species producing marennine have been identified, which opens up the opportunity to explore the diversity within the genus Haslea and, consequently, the diversity of marennines. Marennine-producing representatives of the diatom genus Haslea accumulate the pigment in the apical ends of their cells and also release it into the external environment, thereby giving it a greenish-blue color. Although the exact role of marennine in diatom cellular function is unknown, it is believed to be a photoprotectant that absorbs light in the ultraviolet (UV), violet, and red wavelengths, as it does not participate in photosynthesis. The chemical composition and spectral properties of marennines produced by different species of Haslea vary slightly, although the physical and chemical characteristics of marennine from H. ostrearia have been extensively studied. While the physicochemical properties of marennine in some species, particularly H. ostrearia, have been described in detail, the pigment in H. karadagensis, an endemic species of the Black Sea region, remains largely unexplored. This study presents a comparison of the spectrophotometric and physicochemical characteristics of marennines produced by H. karadagensis and H. ostrearia species under given conditions. The apparent dissociation constants and isobestic points of both diatom species were determined.