Biochemical and biological studies on oleuropein and its hypoglycemic effect

Other Title(s)

دراسات كيميائية حياتية و بايولوجية على الاوليروبين و تأثيره المخفض لمستوى السكر

Dissertant

al-Azzawi, Hasan Fayyd Samir

Thesis advisor

al-Muzaffar, Sami A.

Comitee Members

al-Salihi, Firah G.
al-Dulaymi, Khalid S.
Hasan, Hathama R.
al-Fattahi, Yusuf Ali
Hasan, Ali M. A.

University

University of Baghdad

Faculty

College of Science

Department

Chemistry Department

University Country

Iraq

Degree

Master

Degree Date

2004

English Abstract

The phenolic compounds of three common olea europeae variety leaves, grown in different areas of Iraq (Labeeb, Al-Asharsy and Manzanillo) were studied using different methods of extraction, isolation and purification by thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC).

The dried olive leaves were extracted with methanol: water (1:1 v/v) or ethanol: water (3:1 v/v) until complete extraction of phenolic compounds had been achieved.

The methanolic extract was then conducted to dryness, redissolved in methanol and analyzed by TLC and RP-HPLC.

There was no difference in qualitative phenolic profiles but, different levels of oleuropein were observed in these different varieties.

The polyphenols that detected in olive leaf extract were: hydroxytyrosol, tyrosol, hydroxytyrosol glucoside, caffeic acid, elenolic acid derivatives, verbascoside, rutin, luteolin 7-O glucoside, and apigenin 7-O glucoside.

The recovery of oleuropein was compared between acid and base extraction.

Quantitative data of the levels of phenolic compounds were obtained by the different procedures.

The oleuropein was significantly affected by both acid and base treatment, resulted in the liberation of hydroxytyrosol.

The levels of hydroxytyrosol produced after 24 hour of acid treatment were 50 times than produced by base treatment.

The major phenolic compounds of olive leaves extract were examined and found to be capable of inhibition of low density lipoprotein peroxidation at optimal doses to have remarkable biological activity contributing to that previously reported for the major phenolic compounds.

Oleuropein activity was 49% of mean protection.

Oleuropein and its metabolites, oleuropein aglycone, hydroxytyrosol were compared with vitamin E regard to their antioxidant activity by kinetic studies in a model system.

Oleuropein and hydroxytyrosol were much more efficient than vitamin E as antioxidant.

The II methanolic extract of olive leaves was shown to have inhibitory effects on the hemolysis of rabbit erythrocytes induced by 2, 2-azo-bis-2-amidinopropane (APPH).

Oleuropein exhibited strong antioxidant efficiency against hemolysis of erythrocytes induced by free radicals.

Oleuropein and its metabolites isolated from olive leaves extract were examined in vitro for their antimicrobial activity against five different species of pathogenic bacteria isolated from human patients (E.coli; H.influenza; salmonella typhi; staph.

aureus and K.pneumonia.

The results obtained indicated that all of the phenolic compounds except oleuropein glucoside had antimicrobial activity against all bacterial strains.

Oleuropein was tested for its blood glucose lowering activity in rabbits and showed a dose dependent prophylactic effect against the rise of blood glucose induced by alloxan.

Best results were obtained at a dose of 100 mg/kg of the oleuropein.

In the rabbits that rendered hyperglycemia by alloxan for 16 weeks, and then treated with a dose of 20 mg pure oleuropein daily for further 16 weeks, normalization of the blood glucose was observed.

The effect of the daily intake of 20 mg pure oleuropein in alloxan induced diabetic rabbits on lipid profile, uric acid, glycated hemoglobin, erythrocyte enzymatic antioxidant activity Superoxide dismutase (SOD), Glutathione reductase (GRx), Glutathione peroxidase (GPx), Glucose-6-phosphodehydrogenase (G-6PD), and glutathione (GSH) content, as well as non enzymatic antioxidant levels (vitamin C, vitamin E and β-carotene) in addition to parameters of oxidative stress, thiobarbituric acid reactant substances, and total antioxidant capacity were carried out in two parallel routes: alloxan induced diabetic rabbits administrated 20 mg of oleuropein daily for 16 weeks period and NIDDM patients administrated 1.0 gm of oleuropein daily for 6 months period.

Significant changes in all parameters were observed.

Binding of I-125 insulin to intact human lymphocytes isolated from non insulin dependent diabetes mellitus patients was studied.

The binding characteristics were studied and analyzed by scatchard plot.

There was a high order low capacity binding sites with an affinity constant of 2 x 10 9 M-1 and a low order, high capacity binding sties with an affinity constant of 1.4 x 109 M-1.

The number of binding sites was significantly reduced in noninsulin dependent diabetes mellitus patients against healthy subjects.

Long term administration of 1.0 gm of pure oleuropein daily for 6 months was associated with III improvement in binding percent, protected the insulin receptors from oxidative damage, maintaining its functional integrity, and increase in both order of binding sites although no significant change in affinity constant was observed.

Finally the present study investigated for the first time the effect of oleuropein on histological changes possibly occurring in islets of Langerhans in pancreatic alloxan induced diabetic mice.

Islets of Langerhans showed continuous hypertrophy with hyperplasia, lymphocyte infiltration and a significant increase in the average of islets diameter, while treatment with pure oleuropein showed a decrease average islet diameter with few small islets were atrophoid as a result of oleuropein intake, all of islets appeared normal as of the control animal

Main Subjects

Chemistry

Topics

• Chemistry
• Biology
• Biochemistry

No. of Pages

204

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-599929