الفهرس 
General introdutionOnly 14 pages are availabe for public view
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Abstract
The compounds investigated through out this work were determined
in pharmaceutical preparation and commercial herbal teas. These
compounds include Thymoquinone (TQ), Carvacrol (CR), Thymol (THY),
(−)-Epicatechin (EC), (−)-Epigallocatechin (EGC), (−)-Epigallocatechin
gallate EGCG), Procyanidin B2 (B2), Caffeine (CAF), and L-Glutathione
reduced (GSH).
The thesis consists of four chapters.
Chapter 1:
Includes general introduction about natural antioxidants, the
pharmacological effect of these compounds, their importance, their
classification and the standardization of natural medicines.
Chapter 2:
This chapter divided into:
A- General introduction and historical background about black seed
(Nigella sativa L.), its key constituents, and the traditional use of this herb.
The pharmacological effect of the studied compounds, their structures and
solubility in different solvents.
B- HPLC method was presented for the determination of principal
antioxidants in black seed (Nigella sativa L.) phytopharmaceuticals. The
method was based on HPLC separation and quantitation of TQ, CR and
THY using a reversed-phase C18 analytical column at ambient temperature.
The detector was set at l 254 nm. The mobile phase consisted of water and
methanol in the proportions 40:60 (v/v). The flow rate was 1.5 ml min-1.
The proposed method was validated and successfully applied for
simultaneous analysis of TQ, CR and THY in their pure form and in
commercial formulations. Furthermore, the proposed method is stability
indicating for determination of TQ in presence of its degradants.
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C- Stability study of the principal antioxidants of Nigella sativa (TQ, CR
and THY) has been accomplished by using HPLC method. In addition, the
major degradation products of TQ were investigated and characterized by
LC/MS.
The chromatographic separation of TQ from its hydrolysis products
was performed on C18 column at ambient temperature. RP- LC/MS assay
was carried out using an isocratic system. The mobile phase consisting of
deionized water containing 0.1 % formic acid and methanol in the
proportions 40:60 (v/v), and mass spectra were acquired simultaneously in
positive mode by electrospray ionization mass spectrometry (ESI/MS) in
the mass/charge ratio (m/z) range of 50–1000 during the whole
chromatographic run. The behavior of TQ, CR and THY under different
stress conditions was investigated. The proposed method was used to do
tentative structural identifications based on their molecular weight
measurements of the photo degradants of TQ.
Chapter 3:
This chapter divided into:
A- General introduction and historical background about tea (Camellia
sinensis L.) and grape seed extract (Vitis vinifera L.), their main
phytoconstituents, and the health benefits of their consumption. The
chemical structures of the studied compounds and their solubility in
different solvents.
B- A simple and fast reversed-phase high performance liquid
chromatography with photodiode array detector (RP-HPLC-DAD)
procedure was developed and validated for the analysis of EGC, CAF, B2,
EC and EGCG in 25 different natural complex matrices, containing TE
and/or GSE. The HPLC separation was achieved on a reversed-phase C18
analytical column using an isocratic elution system, separation of all
compounds was achieved in a single step within 12 min. DAD acquisition
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wavelength was set to scan from 200 to 400 nm and all determinations
were performed at ambient temperature.
The proposed method was validated and successfully applied for the
analysis of major catechins, B2 and CAF in different commercial teas,
dietary supplements and their pure form. They have been rapidly and
simultaneously determined with high accuracy and precision, with no
interference from the matrix excipients.
C- HPLC method was developed for simultaneous determination of EGC,
CAF, B2, EC, EGCG, TQ, CR and THY in their pure form and in
commercial formulations. The HPLC method depends on the use of a
reversed-phase C18 column at ambient temperature. A gradient elution was
performed by varying the proportion of solvents. The initial composition of
the mobile phase, consisting of 15 % (v/v) solvent A and 85 % of solvent
B, was maintained for 10 min. Solvent A was then increased linearly to 16
% at 11 min, 17 % at 12 min, 18 % at 13 min, 20 % at 14 min, 30 % at 15
min, 40 % at 16 min and 50 % at 17 min to 31 min. The column was
flushed with 100 % A for 10 min and re-equilibrated for 5 min to starting
conditions for the next run. DAD acquisition wavelength was set to scan
from 200 to 400 nm.
The proposed method was validated and successfully applied for the
determination of each drug in laboratory-prepared mixture and herbal
preparations.
Chapter 4:
This chapter divided into:
A- General introduction and background about glutathione, its biological
functions and its production on an industrial scale. Moreover, the chemical
structure of the studied compound and its solubility in different solvents.
B- The development of simple and accurate RP-HPLC-DAD procedure for
the determination of (GSH) and of its degradant suitable for quality control
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of commercial pharmaceutical formulations. The developed method is
based on isocratic elution system, without sample pretreatment. In addition,
the identification and exact mass measurement of GSH and its degradant by
liquid chromatography coupled with electrospray ionization mass
spectrometry (LC-ESI-MS) were performed.
The chromatographic separation was performed on C18 column at
ambient temperature. RP- LC/MS assay was carried out using an isocratic
system, and mass spectra were acquired simultaneously in positive mode
by electrospray ionization mass spectrometry (ESI/MS) in the mass/charge
ratio (m/z) range of 50–1000 during the whole chromatographic run.
The proposed method was validated and successfully applied for the
analysis of GSH and its degradant in synthetic mixture and in
pharmaceutical preparation. In addition, the major degradant of GSH was
investigated and characterized by LC/MS.