| Titre : | Phytochemicals Screening and Bioactivities of Green Tea Extracts (infusion, decoction, ethanolic) Marketed in the Wilaya of Saida |
| Auteurs : | Rania ZOUBIR, Auteur ; GHOUTI, Dalila, Directeur de thèse |
| Type de document : | texte imprimé |
| Editeur : | Dr. Moulay Tahar Université Saida, Faculté des Sciences Naturelles et de la Vie, 2025/2026 |
| Format : | 110 p / 29 CM |
| Accompagnement : | CD |
| Langues: | Anglais |
| Langues originales: | Anglais |
| Catégories : | |
| Mots-clés: | Green tea (Camellia sinensis) ; El-Berrad ; El-Raqim ; Antioxidant activity ; Anti-inflammatory activity ; antimicrobial activity ; IC₅₀ |
| Résumé : |
This study evaluates the biological activities of three extracts (infusion, aqueous
and ethanolic decoction) from Camellia sinensis (green tea) leaves, using two commercial brands consumed in Saida: "El-Berrad" and "El-Raqim". Phytochemical screening revealed an abundance of flavonoids, tannins, alkaloids, and sterols, a weak presence of coumarins and saponins, and a total absence of anthocyanins. The ethanolic extracts demonstrated remarkable DPPH radical scavenging activity with IC₅₀ values of 0.014 mg/ml for "El-Berrad" and 0.015 mg/ml for "El-Raqim", followed by aqueous decoctions (IC₅₀ = 0.16 and 0.12 mg/ml respectively), while the hot infusion showed the lowest activity. For the FRAP assay, the ethanolic extract of "ElRaqim" was the most promising (IC₅₀ = 0.036 mg/ml). Anti-inflammatory activity (HRBC assay) showed maximum membrane stabilization of 68.14% for "El-Berrad" and 69.03% for "El-Raqim" at the highest concentration. The antimicrobial assay via well diffusion targeted four bacterial strains (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Bacillus cereus) and two fungal strains (Penicillium zacinthae, Aspergillus niger). The ethanolic extract had the greatest effect against Staphylococcus aureus (inhibition zones of 6–16 mm for "El-Berrad" and 6– 15 mm for "El-Raqim") with a MIC of 1.09 mg/ml for both brands. No activity was recorded against Escherichia coli or the fungal strains. Finally, the MBC test demonstrated a bacteriostatic rather than a bactericidal effect. In conclusion, these results confirm a high biological convergence between both brands and suggest that reflux decoction optimizes bioactive compound extraction compared to the infusion method. |
| Note de contenu : |
Contents:
List of Abbreviations :.....................................................................................................3 Introduction.............................................................................................................................13 Introduction: ..........................................................................................................................14 Part one:..................................................................................................................................16 Chapter I : ...............................................................................................................................17 I.1 History and Origin of Tea : ...................................................................................18 I.2 Botanical Study of Camellia sinensis:..................................................................19 I.2.1 Definition :..........................................................................................................19 I.2.2 Nomenclature and Taxonomy :.........................................................................19 I.2.3 Taxonomy: ..........................................................................................................20 I.2.4 Botanical description :.......................................................................................21 I.3 Geographical Distribution and Ecology :............................................................24 I.3.1 Botanical Varieties: A Comparative Overview : .............................................25 I.4 Cultivation and Biochemical Processing..............................................................25 I.5 Uses and Potential Applications of Tea ................................................................28 Chapter II :..............................................................................................................................31 II.1 Phytochemical Profile of Green Tea (Camellia sinensis):...................................32 II.1.1 The Polyphenolic Complex (20–30% of Dry Weight) : ..............................32 II.1.2 Alkaloids :.......................................................................................................34 II.1.3 Amino Acids: ..................................................................................................35 II.1.4 Organic Acids, Carbohydrates, and Minerals.............................................35 ..........................................................................................................................................36 II.1.5 Lipids and Sterols (1–2% dry weight) :.......................................................36 II.1.6 Additional Vitamins :.....................................................................................36 II.1.7 Pigments and Enzymes..................................................................................36 II.1.8 Volatile Aromatic Compounds (Aroma Profile):........................................36 II.2 Biological Activities :..............................................................................................38 II.2.1 Antioxidant Activity : ...................................................................................38 II.2.2 Anti-inflammatory Activity: .........................................................................42 II.2.3 Antimicrobial activity:...................................................................................44 Table of contents. Part Two:.................................................................................................................................47 Chapter III...............................................................................................................................48 III. Materials and Methods..............................................................................................49 III.1 Introduction: ..........................................................................................................49 III.2 Plant Materials.......................................................................................................49 III.3 preparation of Extracts .........................................................................................50 III.3.1 Aqueous Infusion ...........................................................................................50 III.3.2 Aqueous Decoction (Reflux Extraction): .....................................................50 III.3.3 Ethanolic Decoction (Ethanolic Extraction):...............................................51 III.3.4 Extraction Yield .............................................................................................52 III.4 Phytochemical Screening : ....................................................................................52 Flavonoids :.....................................................................................................................52 Tannins :..........................................................................................................................52 Coumarins Test : ............................................................................................................53 Reducing Compounds....................................................................................................53 Saponins..........................................................................................................................53 Starch ..............................................................................................................................53 Anthocyanins Test:.........................................................................................................53 Alkaloids Test .................................................................................................................53 Sterols and Triterpenes: ................................................................................................54 III.5 Evaluation of Antioxidant Activity:......................................................................54 III.5.1 DPPH Free Radical Scavenging Assay: .......................................................55 III.5.2 Ferric Reducing Antioxidant Power (FRAP) Assay : .................................56 III.6 The anti-inflammatory activity test: ....................................................................57 III.6.1 Red Blood Cell (Erythrocyte) Membrane Stabilization Test:....................57 III.7 Antibacterial Activity Assay : ...............................................................................59 III.7.1 Experimental Procedure : .............................................................................59 III.7.2 Determination of Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) :..........................................................61 Chapter IV...............................................................................................................................62 IV.1 Extraction Yield:....................................................................................................63 IV.2 Phytochemical Screening of Green Tea Extracts :..............................................64 Table of contents. IV.3 In vitro biological activities of Camellia sinensis extracts : ...............................69 IV.3.1 Antioxidant activity:......................................................................................69 IV.3.2 Anti-Inflammatory Activity :........................................................................75 IV.3.3 Antimicrobial activity :..................................................................................78 Conclusion...............................................................................................................................93 Bibliographic References........................................................................................................96 Annexes.................................................................................................................................105 |
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