Browsing by Author "Christodoulou, Maria"

The rapid emergence of drug resistant pathogens prevents effective treatment of diseases and threatens the lives of millions of people. Similarly, resistance to chemotherapeutic agents has been observed in several types of cancer. Therefore, screening for novel antimicrobial and antileukemic substances is urgently needed. Screening microorganisms for bioactive molecules has resulted in the discovery of several substances that are currently used for disease treatment. Cyanobacteria represent an ancient group of oxygenic, photosynthetic prokaryotes that produce a variety of functionally diverse and structurally complex natural compounds, some of which have already been used as source of inspiration in drug development process. In this study, I evaluated the antimicrobial and antileukemic potential of filamentous cyanobacteria against Gram-positive, Gram-negative and fungal potential pathogens and acute myeloid leukemia (AML) MOLM-13 cell line. Extracts showing antibiotic and/or antileukemic activity were subjected to reversed-phase HPLC and individual fractions were re-evaluated for their ability to kill the abovementioned pathogens and/or induce cell death in MOLM-13 cell line. Metabolites present in the active HPLC fractions were analysed by UPLC/ESI/Q-TOF and elemental compositions were obtained. Identification of metabolites was accomplished by searching online databases for compounds with identical elemental composition. Chemical structures were further confirmed by comparing mass spectrometry data with publicly available data. New bioactive metabolites, new variants of known metabolites and a number of yet unidentified metabolites exhibiting antimicrobial and/or antileukemic activity are reported herein. In detail, novel metabolites belonging to aromatic polyketides and their new variants were present in the active fractions of Nostoc sp. CENA69. The cyanobacterium Aliinostoc sp. CENA513 produced the recently discovered metabolite nocuolin A, a compound with antimicrobial and antiproliferative properties, lipids and unidentified lipidic compounds that showed only bactericidal activity against B. cereus. Interestingly, none of the abovementioned strains had any effect on the growth of Gram-negative pathogens. Planktothrix agardhii UHCC 0018 and Anabaena sp. UHCC 0187 strains showed only antileukemic activity. The majority of the bioactive fractions deriving from these two strains contained either lipids or pigments and their derivatives. The remaining active HPLC fractions of these two strains contained a great number of unidentified compounds. Further studies are required to identify the unknown compounds and purify the novel metabolites and antibacterial lipids. The results presented herein clearly show that Cyanobacteria are an emerging source of bioactive metabolites that can be used in drug development process or act as a source of inspiration for the production of novel synthetic drugs.