Part I: Background
1.1.4. Phytochemical Review of OOBPs
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1.1.3. Recovery and Reuse of the Components from OOBPs (OMW and Leaves)
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a secoiridoid group member and its hydrolysis derivative; hydroxytyrosol are the most studied olive biophenols 17. In general, even though the phenolic compounds are known to be the major contributors to the toxicity of OMW 10, they are endowed with several biological activities such as antioxidant properties 18–20. This has led to the proposal of the production of biologically active compounds such as phenolic antioxidants from OMW constitutes as a viable alternative for valorizing this problematic waste 18.
Following a long-time recognition of the antioxidant activity of OMW and the association of oxidative stress such as ROS with many diseases, it was logical to consider OMW as a potential source of biophenolic antioxidants. In this section, the olive biophenol metabolites, with their biological properties have been reviewed.
Phenolic Content
The phenolic profiles of olive fruit and the corresponding oil (VOO), leaves, and OMW obtained either from the industry or by the laboratory-scale press has been compared in previous works 12,18,21–25. In general, the chromatogram profiles of the fruit showed similarity to that of the OMW where secoiridoid glycosides were present in high concentration. In contrast, many studies found out that secoiridoid derivative, hydroxytyrosol was found in higher amounts in the OMW than in the VOO and olive leaves 12,21. This poor correlation between the phenolic content of the fruits and that of the OMW has been ascribed to several factors involved during extraction – the effects of processing 13,26. However, it is worth mentioning that OMW has been
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proven to be richer in biophenols as compared to oil, fruits, or olive leaves 12. Table 2 and 3 below shows some of the biophenols reported in OOBPs and their reported biological activities and their chemical structures.
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Table 2: The Major Biophenols in OOBPs (OMW and olive leaves) and Their Reported Activities
Biophenol Bioactivity Remark(s)
Oleuropein 21 Antioxidant From olive cake extract 27. In vivo and in vitro activity 28,29. Free radical scavenging activity 30,31. Cardioprotective Inhibition of LDL oxidation and platelets
aggregation 32,33.
Fatty acid composition of rat heart 34,35. Enhances nitric oxide production
Antiulcer Prevents ethanol-induced gastric ulcers 36. Hypoglycemic Reduces blood sugar in rats – normal and
diabetic 37,38. Antihypertensive Vasodilator 39.
Anti-inflammatory Prostaglandin sparing and analgesic effect
40.
Inhibition of 5-lipoxygenase 41. Antimicrobial Antibacterial 42.
Antimycoplasmal 43. Antifungal effects 44.
Anti-HIV activity of olive leaf extract 45. Endocrinal activity Thyroid stimulation 46,47.
Neuroprotective Neuroprotective following spinal cord injury in rats 48.
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Biophenol Bioactivity Remark(s)
Neuroprotective against cognitive
dysfunction in hippocampal CA1 area in rats 49
In vitro and epidemiological 32. Hydroxytyrosol
18,21,50–52 Antioxidant Isolated from OMWW, antioxidant in rats, and liver cells 53,54.
Protects human erythrocytes against oxidative damage 55.
Cardioprotective scavenges and reduces superoxide anion production in human promonocyte cells 56,57. Chemopreventive Protective against oxidative stress in kidney
cells 58.
Cancer chemoprevention through G1 cell cycle arrest and apoptosis 59.
Induces cytochrome C-dependent apoptosis 60.
Inhibition of the proliferation of tumor cells 59. Antimicrobial Antibacterial 42.
Antimycoplasmal 43. Antiviral 61.
Anti-inflammatory Prostaglandin sparing 40.
Inhibition of leukocytes leukotriene B4 62. Impairs Cytokine and Chemokine
Production in Macrophages 63. inhibition of 5-lipoxygenase 41. Skin lighting
property
topical and bath preparation 52.
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Biophenol Bioactivity Remark(s) Age-related
dementia (Alzheimer’s disease)
Restores proper insulin signaling in an astrocytic model of Alzheimer's disease 64 Improves cognitive function in Rats 65. Tyrosol 27,50 Antioxidant Restored intracellular antioxidant defense
66.
DPPH scavenging 67
Protect against oxidized LDL 68.
Chemopreventive Protective against oxidative stress in kidney cells 58.
Anti-inflammatory Inhibition of 5-lipoxygenase (less active than HT) 41.
Caffeic acid
19,69
Antioxidant Stabilized oxidative stress 70
Anti-inflammatory Inhibition of 5-lipoxygenase (less active than HT and tyrosol) 41.
Chemoprotective Inhibits DNA oxidation (less active than hydroxytyrosol but more efficient than tyrosol in prostate cells 71.
Antimicrobial Antibacterial 72. Antifungal 72. Verbascoside
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Antioxidant Isolated from OMWW 73. Food antioxidants 73.
Antioxidant in Rats by TEAC assay 51. Chemoprevention Protects the human keratinocyte against
solar UV 74.
Antiplatelet Inhibits ADP and arachidonic acid-induced platelet aggregation 75.
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Biophenol Bioactivity Remark(s)
Antihypertensive Angiotensin-converting enzyme (ACE) inhibitor 76.
Anti-inflammatory Multiple mechanisms 77. Rutin 78 Antioxidant In vitro antioxidant 79.
Anti-inflammatory Intestinal anti-inflammatory effects in the CD4+ CD62L+ T cell transfer model of colitis 80.
Anti-inflammatory on rat paw oedema, and on neutrophils chemotaxis and
degranulation 81.
Antihyperglycemic Antihyperglycemic in Streptozotocin-Induced Diabetic Wistar Rats 82.
Chemopreventive Attenuates intestinal toxicity induced by Methotrexate 83.
p-coumaric acid 69
Antioxidant Scavenges the reactive oxygen species (ROS) in Rats 84.
Minimizes the oxidation of LDL in Rats 84. Protects the rat heart from the oxidative stress of doxorubicin 85.
Antioxidant in multiple in vitro cell-free systems; DPPH, ORAC, SOSA, & ABTS 86. Antimicrobial Inhibits the Listeria monocytogenes RecA
protein function 87.
General antimicrobial 88.
Chemopreventive Chemopreventive via induction of Nrf2 in colon cancer 89.
Anticancer against HCT-15 colon cancer cells
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Biophenol Bioactivity Remark(s) Vanillic acid
21,69
Antioxidant Protective effects on lipid peroxidation in cardiotoxic Rats 90.
Antioxidant in multiple in vitro cell-free systems; DPPH, ORAC, OxHLIA, ABTS 91. Antimetabolic
syndromes
Reduced risks in high fat-induced diabetic hypertensive Rats 92.
Antimicrobial Antibacterial 45. Antifungal 45.
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Table 3: Chemical structure of main phenolic compounds found in by-products of olive oil production
Class (Group) Chemical Structure Compound
Secoiridoids Oleuropein: R1=OH,
R2=CH3, R3=Glucose 3,4-DHPEA-EA: R1=OH, R2=CH3, R3=H
Ligstroside: R1=H, R2=CH3, R3= Glucose
Phenylalcohols Hydroxytyrosol: R1=OH,
R2=H
Tyrosol: R1=H, R2=H Hydroxytyrosol glucoside: R1=OH, R2=Glucose
3,4-DHPEA-EA: R1=OH p-HPEA-EA: R1=H
Phenolic acids/
aldehyde
Caffeic acid: R1=OH;
R2=H
p-Coumaric acid: R1=H;
R2=H
Ferulic acid: R1=H;
R2=OCH3
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Class (Group) Chemical Structure Compound
Gallic acid: R1=OH;
R2=OH; R3=OH Vanillic acid: R1=OH;
R2=OCH3; R3=H Protocatechuic acid:
R1=OH; R2=OH; R3=H Vanillin: R1=H; R2=OCH3; R3=H
Flavonoids Rutin: R1=OH; R2
=O-rutinose; R3=OH Luteolin:
R1=OH; R2=H; R3=OH Luteolin-7-O-glucoside:
R1=OH; R2=O-glucose;
R3=OH
Apigenin: R1=OH; R2=H;
R3=H
Apigenin-7-O-glucoside:
R1=OH; R2=O-glucose;
R3=H Phenylethanoid
glycoside
Verbascoside
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Class (Group) Chemical Structure Compound Lignans
Pinoresinol, R1=H 1-acetoxypinoresinol, R1=Ac
3,4-DHPEA-EA: oleuropein aglycon mono-aldehyde; 3,4-DHPEA-EDA: oleuropein-aglycone di-aldehyde; p-HPEA-EDA: ligstroside-oleuropein-aglycone di-aldehyde
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