Lipophilic extracts of the thermophilic cyanobacterium Leptolyngbya sp. and chlorophyte Graesiella sp. and their potential use as food and anticancer agents

Abstract

The lipophilic extracts from the cyanobacterium Leptolyngbya sp. and the microalga Graesiella sp. collected from a hot spring in northern Tunisia were investigated and evaluated for their anti-proliferative effects. From the dry biomasses, total lipid content was obtained with yields of 28.8 and 13% (w/w) for Graesiella sp. and Leptolyngbya sp., respectively. Compositional analysis showed an abundance of saturated fatty acids dominated in Graesiella sp. by palmitic, margaric, myristic, lauric and tridecanoic acids. Oleic, linoleic, linolenic and elaidic acids were found as the main unsaturated fatty acids. Leptolyngbya sp. shared with the microalgal species its richness in palmitic, oleic and linoleic acids, but it is distinguished by high abundance of pamitoleic acid. Besides their adaptive significance to thermophilic conditions, fatty acid profiles exhibited good nutritional properties especially for Graesiella sp. as revealed by their low atherogenic, thrombogenic and hypocholesterolemic indices and high to moderate levels of ω3 PUFA. Analysis of the predicted physico-chemical properties of the prospective biodiesel utility showed in the case of Graesiella sp. that most parameters including saponification value, iodine value, cetane number and oxidation stability adhered to the American ASTM-D6751 and/or the European EN 14214 specifications. The lipophilic extract was further analyzed by gas chromatography coupled with mass spectrometry and its anti-proliferative activity was measured. Results showed the abundance of diterpenes (neophytadiene, phytol), alkanes/alkenes (pentacosane, heptacosane), sterols (γ-sitosterol), and terpenes (limonene), among others in both extracts. The in vitro assays revealed that both lipophilic fractions concentration-dependently inhibited the proliferation of the human ovarian SK-OV-3 and colon DLD-1cancer cell lines. Collectively, results of the present study indicate that lipophilic fractions of Leptolyngbya sp. and Graesiella sp. hold potential to be exploited as an excellent candidate for the development of natural food supplements and anti-proliferative agents.