Abstract
Abstract:
This thesis mainly aims to extract saponins and carotenoids from two echinoderm Asteroidea
Echinaster sepsoitus and Ophidiaster ophidianus by two extraction methods namely
microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE).
The application of response surface methodology (RSM) coupled with a Box–Behnken design
to optimize MAE and UAE conditions (the solvent concentration, irradiation time, microwave
power, and liquid-solid ratio and microwave power) allows to describe the two extraction
methods by second order polynomials models, and to predict the optimal extraction conditions
of saponins and carotenoids by MAE and UAE.
The optimized MAE and UAE were compared with conventional solvent extraction. The
results demonstrated that MAE allowing higher recovery yield of saponins and carotenoids
with a shorter extraction time and a lower solvent consumption. MAE was found to be the
most efficient method for the extraction of saponins and carotenoids from E. sepositus and O.
ophidianus.
Screening of E. sepositus saponins mixtures obtained from different organs (the stomach, the
pyloric caeca, the gonads, the oral body wall and aboral body wall ) by mass spectrometry
(HR-ESI-MS and HR-ESI- MS/MS) demonstrated that the diversity of saponins in E.
sepositus is higher than previously reported. We highlighted 11 different saponins, including
9 new congeners. Presumptive molecular structures are proposed for 6 molecules on the basis
of key-fragmentations identified by HR-ESI-MS/MS. The structures of major saponins
compounds (sepositoside and luzonicoside) were elucidated by 1 D and 2 D NMR
experiments.
The comparison of the saponin contained in the five body components of E .sepositus
revealed qualitative and quantitative variability in saponins distribution. This heterogeneity
was linked to the organ, sex and the collecting season.
From the in vitro antioxidant test we have noted that studied molecules inhibit DPPH radical
and electro-generated superoxide radical (O2
•). In addition saponins at a non-hemolytic
concentration (1mg.L
-1 ) exhibited some inhibitory activity toward hemolysis induced by
hydroxyl radical OH - .
Keywords:
Starfish, ultrasound assisted extraction, microwave assisted extraction, saponis, carotenoids,
high resolution mass spectrometry.
Abstract:
This thesis mainly aims to extract saponins and carotenoids from two echinoderm Asteroidea
Echinaster sepsoitus and Ophidiaster ophidianus by two extraction methods namely
microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE).
The application of response surface methodology (RSM) coupled with a Box–Behnken design
to optimize MAE and UAE conditions (the solvent concentration, irradiation time, microwave
power, and liquid-solid ratio and microwave power) allows to describe the two extraction
methods by second order polynomials models, and to predict the optimal extraction conditions
of saponins and carotenoids by MAE and UAE.
The optimized MAE and UAE were compared with conventional solvent extraction. The
results demonstrated that MAE allowing higher recovery yield of saponins and carotenoids
with a shorter extraction time and a lower solvent consumption. MAE was found to be the
most efficient method for the extraction of saponins and carotenoids from E. sepositus and O.
ophidianus.
Screening of E. sepositus saponins mixtures obtained from different organs (the stomach, the
pyloric caeca, the gonads, the oral body wall and aboral body wall ) by mass spectrometry
(HR-ESI-MS and HR-ESI- MS/MS) demonstrated that the diversity of saponins in E.
sepositus is higher than previously reported. We highlighted 11 different saponins, including
9 new congeners. Presumptive molecular structures are proposed for 6 molecules on the basis
of key-fragmentations identified by HR-ESI-MS/MS. The structures of major saponins
compounds (sepositoside and luzonicoside) were elucidated by 1 D and 2 D NMR
experiments.
The comparison of the saponin contained in the five body components of E .sepositus
revealed qualitative and quantitative variability in saponins distribution. This heterogeneity
was linked to the organ, sex and the collecting season.
From the in vitro antioxidant test we have noted that studied molecules inhibit DPPH radical
and electro-generated superoxide radical (O2
•). In addition saponins at a non-hemolytic
concentration (1mg.L
-1 ) exhibited some inhibitory activity toward hemolysis induced by
hydroxyl radical OH - .
Keywords:
Starfish, ultrasound assisted extraction, microwave assisted extraction, saponis, carotenoids,
high resolution mass spectrometry.