Contribution à la valorisation de la flore d’Algérie : Etude phytochimique et biologique des espèces Origanum floribundum Munby et Daucus virgatus (Poir.) Maire

Abstract

The research documented in this thesis makes a valuable contribution to the valorization of Daucus virgatus (Poir.) Maire and Origanum floribundum Munby are both endemic species to Algeria. In order to isolate and characterize the flavonoid compounds present in O. floribundum, an extensive phytochemical analysis was performed. This involved the utilization of chromatographic techniques, including TLC, CC, HPLC, and LC/MS, in addition to primarily spectroscopic structural determination methods like UV-Vis and NMR. A total of five flavonoids were extracted from this species, with luteolin and four methoxylated flavones constituting the majority, and upon analysis with coupled LC-DAD-APCI-MS/MS, the CH2Cl2, AcOEt, and n-BuOH extracts revealed the presence of five flavonoids and four phenolic acids. The prenylated flavone Kanzonol E and the compounds rhododendrine were not previously identified within the genus Origanum; this is the first citation for this genus. In a similar fashion, vicenine-2 was first identified in this species. The results of a quantitative assessment of total flavonoids (TFC) and total polyphenols (TPC) indicated that the ethyl acetate extract contained the highest concentration of polyphenols (446.5% EAG/mg extract), followed by the butanol extract at 340,6% EAG/mg extract. On the contrary, the dichloromethane extract exhibited a peak flavonoid concentration of 34.30 µg EQ/mg. Analytical activity assessment of the examined extracts via various techniques (DPPH, ABTS, CUPRAC, and ferric reducing power) unveiled antioxidant and radical scavenging properties that were not only intriguing but also quite potent. It is worth noting that the ethyl acetate extract demonstrated the most robust antioxidant activity compared to all other experiments performed. The radical scavenging activity of the examined extracts was found to be more pronounced when the ABTS.+ radical cation was utilized, as opposed to the DPPH. free radical. Furthermore, it was observed that the butanol extract demonstrated the highest ferrous ion-reducing capacity (A0.50=4,50 µg/ml), which exceeded the capacities of BHA and ascorbic acid. For all three extracts, a positive correlation was found between antioxidant activity and both TPC and TFC. In order to assist in the process of valorizing the essential oil (EO) of D. virgatus, a chemical compositional analysis utilizing GC-MS was performed on the plant. This investigation unveiled the existence of twenty-one compounds. -pinene (77,9%) and -pinene (7,6%) constituted the most abundant constituents. The antimicrobial activity against one yeast and six microorganisms was evaluated. The findings indicated that the essential oil (EO) possessed noteworthy antimicrobial properties, specifically against C. albicans and S. typhimurium. These microorganisms exhibited the highest sensitivity, as evidenced by inhibition zones spanning a range of 2,3 to 25 mm and minimal inhibitory concentrations of 15,63 and 31,25 μg/ml, respectively. The EO exhibited a moderate antioxidant effect in the DPPH assay, as indicated by its IC50 value of 39,61 mg/ml. Comparatively, the EO of D. virgatus and the positive control Acarbose demonstrated substantial inhibitory effects on the α-glucosidase enzyme (IC50=0.35 mg/ml; IC50=0,24 mg/ml, respectively). Furthermore, a significant inhibitory impact on cholinesterase enzymes was detected, as evidenced by IC50 values for acetylcholinesterase and butyrylcholinesterase ranging from 0,33 to 0,20 mg/ml, respectively. Based on these results, the two species under investigation may contain a vast array of bioactive compounds, which could be utilized to develop therapeutic pharmaceuticals. Additionally, they emphasize that compounds possessing antioxidant, antimicrobial, anti-Alzheimer's, and antidiabetic properties may be abundant in these plants.