The occurrence of the cis/trans geometric isomerism of myxoxanthophyll and 4-ketomyxoxanthophyll in the cyanobacterium Anabaena sp. PCC7120

The cyanobacteria of the genus Anabaena have recently been recognized as a potential source of secondary metabolites of pharmacological and biotechnological importance. In particular, myxoxanthophylls – specific carotenoid glycosides that accumulate in cyanobacterial cells, are attracting increasing interest. Anabaena (Nostoc) sp. PCC7120, a filamentous, mesophilic, nitrogen-fixing cyanobacterium, is a model organism used in biochemical and genetic studies. The carotenoid pool of Anabaena sp. PCC7120 consists of five main species of pigments, namely β-carotene, echinenone, canthaxanthin and two derivatives of myxoxanthophyll: myxoxanthophyll ((3R,2‘S)-myxol 2’-fucoside) and 4-ketomyxoxanthophyll ((3S,2’S)-4-ketomyxol 2’-fucoside). Recent findings show that the carotenoid biosynthesis pathway functions in Anabaena sp. PCC7120 cells are affected by environmental factors. Specifically, the balance between β-carotene and ketocarotenoids alters according to the temperature conditions. In this study, a new method, based on single-step liquid adsorption chromatography was developed and applied to separate a fraction containing myxoxanthophyll and 4-ketomyxoxanthophyll from Anabaena sp. PCC7120 cells. It was found that this method allowed a high purity fraction of carotenoid glycosides to be obtained from pigment pools as extracted from cyanobacterial cells. The subsequent analysis using the methods HPLC and LC/MS demonstrated that this fraction consists of a mixture of compounds with different retention times. On the basis of their fragmentation spectra and optical properties, these compounds were identified as geometrical isomers of myxoxanthophyll and 4-ketomyxoxanthophyll, including the dominant all-trans forms and less abundant cis forms. Proposals regarding the structures of myxoxanthophyll isomers are made

Isolation and preliminary characteristics of antioxidant properties of myxoxanthophyll

Karotenoidy są bardzo rozpowszechnioną w przyrodzie grupą związków chemicznych. Przedstawicieli tej rodziny jest bardzo wielu i występują we wszystkich królestwach organizmów żywych. Pełnią istotne funkcje, z których podstawową jest współudział w fotosyntezie. Nie do pominięcia jest także ich rola fotoprotekcyjna, jak również to, że odpowiadają za kolor kwiatów, liści czy piór. Pełnią także inne role fizjologiczne m. in. w procesie widzenia. Stanowią także obiekt zainteresowania dietetyki i medycyny z powodu właściwości antyoksydacyjnych.Jednym z karotenoidów jest miksoksantofil – fukozyd miksolu. To jeden z rzadko występujących glikozydów karotenoidów. Jest obecny w sinicach. Jego fizjologiczna rola nie jest w pełni wyjaśniona, wydaje się, że stanowi część aparatu chroniącego komórkę przed stresem oksydacyjnym. Nie został także scharakteryzowany fizykochemicznie.W pracy przedstawiona została prosta i efektywna metoda uzyskiwania miksoksantofilu z Synechocystis sp. PCC 6803 metodą klasycznej chromatografii cieczowej.Ponadto, przedstawiono charakterystykę widmową miksoksantofilu w zakresie spektroskopii absorpcyjnej UV-Vis w różnych środowiskach. Dodatkowo, pokazano uzyskane widma dichroizmu kołowego w roztworach.Dokonana została także wstępna ocena właściwości przeciwutleniających miksoksantofilu dwoma niezależnymi metodami – z wykorzystaniem rodnika DPPH oraz ORAC.Carotenoids are group of chemical compounds which are widespread in nature. They are plentiful among all kingdoms of living organisms. They have very versatile and important functions. The most fundamental is complicity in photosynthesis. Not to forget is their photoprotective role. Carotenoids are also colourants of flowers, leaves or birds' feathers. Other physiological function which they take part in is for example seeing process. Due to their antioxidant properties they are also object of interest of medical and food researchers.Myxoxanthophyll (fucoside of myxol) is one of the rare glycosides of carotenoids. It occurs in cyanobacteria. Physiological role of myxoxanthophyll isn't fully explained. It is speculated that it is part of defense mechanisms against oxidation stress. Also, it is not characterized by means of physical chemistry.Simple, effective and inexpensive method of obtaining myxoxanthophyll from Synechocystis sp. PCC 6803 by using liquid chromatography is shown. Moreover, UV-Vis absorption and circular dichroism spectra in various environments are presented.Preliminary characteristics of antioxidant capacity has also been made using two independent methods - with using DPPH radical and ORAC

Photosynthetic efficiency in Polish and Australian Raphidiopsis raciborskii strains

Raphidiopsis raciborskii, as a potentially toxic, invasive cyanobacteria has attracted great attention. Worldwide distribution could have contributed to its phenotypic plasticity and even the formation of ecotypes adapted to the local environment. To determine mechanisms responsible for the omnipresence of R. raciborskii, photosynthetic efficiency in several strains differing in origin and toxicity has been investigated. Three non-toxic Polish strains and two toxic Australian strains were grown under standardized light and temperature conditions. Concentration of photosynthetic pigments, qualitative and quantitative analysis of carotenoid composition, and photosynthetic performance (chlorophyll fluorescence in vivo) were analysed. No significant differences between strains were observed in the photosystem II quantum efficiency (Fv/Fm), the photochemical (qP) and non-photochemical quenching (NPQ) and dark and light levels of plastoquinone reduction. Nonetheless, a positive correlation between Fv/Fm and overall NPQ was found. The phycocyanin concentration was negatively correlated with the carotenoid concentration in all five examined strains. Furthermore, in four strains roughly one third of pigments consisted of myxoxanthophylls. The ability to accumulate pigments involved both in light harvesting and photoprotection may contribute to the optimization of photosynthetic efficiency of investigated R. raciborskii strains in different environmental conditions. Documented parameters could not be ascribed to the difference in growth conditions, but could result from variations in their genetics