Στοιχεία επταμελούς επιτροπής:
Supervisor: Assoc. Prof. Nektarios Aligiannis Department of Pharmacy School of Health Sciences NKUA
Co-supervisors: Asst. Prof. Nikolas Fokialakis Department of Pharmacy School of Health Sciences NKUA
Dr. Aikaterini Termentzi Researcher in Benaki Phytopathological Institute
Referee committee: Prof. Nicholas H. Oberlies University of North Carolina at Greensboro USA
Prof. Maria-Ioanna Chinou Department of Pharmacy School of Health Sciences NKUA
Prof.Evangelos Gikas Department of Analytical Chemistry, School of Science NKUA
Asst. Prof. Khaled A. Shaaban Pharmaceutical Sciences Dept. College of Pharmacy, University of Kentucky, USA
Περίληψη:
This dissertation investigates natural products from two fungi isolated from different biological sources. The identification of the purified fungi was preliminary based on culture and microscopic characteristics next, the obtained sequence was deposited in the GenBank nucleotide sequence database with a specific accession number. The isolates were scaled up under standard conditions, and the culture broths were usually extracted with ethyl acetate. The crude extracts were purified using various chromatographic methods, including CPC, silica gel columns, Sephadex LH-20, PTLC and HPLC. The isolated compounds were dereplicated by means of the Dictionary of Natural Products (DNP) and the Chemical Abstracts. Structure elucidation of novel compounds required application of more advanced NMR techniques such as HSQC, HMBC, and NOESY. Assigning absolute configuration was often the most difficult task in characterizing individual metabolites. To assign absolute configuration of the peptides encountered, a process of 2D NOESY and optical rotation were employed.
In general, many of the isolated compounds were investigated for various biological activities (e.g. as antimicrobial, antienzymatic agents,… etc.).
The crude extract of the soil-derived fungus Aspergillus ochraceopetaliformis which collected at Giza province, Egypt and cultivated in rice medium, exhibited significant antimicrobial activity against several pathogenic test microorganisms based on paper-disk diffusion assay.
In the TLC screening, the extract showed a low polar yellow band and numerous UV absorbing and fluorescent zones. The extract was defatted using cyclohexane and the methanolic part was pre-separated by column chromatography using silica gel. Further purification on Sephadex LH 20, by PTLC and HPLC, afforded 24 compounds, belonging to different chemical families.
19 alkaloids among them 4 new compounds named 8-OH-Echinulin (38), 27-28-epoxyechinulin (39), and neoechinulin F (46) and (12R)dehydroechinulin (49), as well as two cyclic peptide compounds Cyclo[Ala-Trp] (33), and Cyclo[Trp-Val] (41), six prenylated alkaloids (echinulin-type) preechinulin (34), tardioxopiperazine B (35), tardioxopiperazin A (36), echinulin (37), and Cyclo‐L‐2‐tert‐DMA‐4,5,7‐tri‐DMA‐Trp‐L‐Ala (40) which reported only one time as a minor compound and one indole diketopiperazine dimer eurocristine (42).
The other alkaloids were (neoechinulin-type) like neoechinulin A (43), variecolorin G (44), neoechinulin (45), neoechinulin D (47), dehydroechinulin (49), cryptoechinulin D (50), and cryptoechinulin B (51) and cristatumin D (48) which had open ring. Moreover, a new ochraceopyronoid (52) which had a rare lyxofuranosid, isotorachrysone-6-O-α-D-ribofuranoside (53) and the rare triterpene 2-α-hydroxydiploptero (54) which reported one time only. Besides, two anthraquinone derivatives named questin (55), and physcion (56) were identified. All of the isolated compounds have been tested for antimicrobial activity against several pathogenic microorganisms.
To the best of our knowledge, all of these metabolites were recorded for the first time from Aspergillus ochraceopetaliformis
Λέξεις-κλειδιά:
Alkaloids; amino acids; anthraquinones; antimicrobial activities; Aspergillus; chromatographic techniques; cyclic peptides; diketopiperazine alkaloids; endophytic fungi; indole alkaloids; lyxofuranoside; miophytocens; Myrothecium; natural products; NMR spectroscopic; phytochemistry; prenylated indole alkaloids; roridins; terrestrial fungi; trichothecenes; tichoverrins; trichoverroids; triterpenes; verrucarins
