الفهرس 
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Abstract
The study was conducted at the Arid Land Lab., Arid Land Agricultural Graduate Studies and Research Institute (ALARI), Ain Shams University.
Bioactive compounds play different important roles in human health as antioxidant, anti-inflammatory, antimicrobial and anticancer etc, but the utilization of these compounds is restricted by their sensitivity towards different environmental conditions like heat, pH, O2 and light. In addition to their poor solubility. So the aim of this study was to improve the stability, solubility and bioavailability of these compounds.
The results of this study could be summarized as follows:
5.1 Preparation and characterization of encapsulated plant extracts
Four different extracts from natural plant sources grown in arid lands (Red cabbage, Ginger, Curcumin, and Tomato) were prepared and encapsulated each one with β-cyclodextrin (CD) and maltodextrin (MD) by freeze drying process.
All the prepared encapsulated plant extracts; encapsulated red cabbage extract with β-cyclodextrin (R-CD), encapsulated red cabbage extract with maltodextrin (R-MD), encapsulated ginger extract with β - cyclodextrin (G-CD), encapsulated ginger extract with maltodextrin (G- MD), encapsulated curcumin extract with β-cyclodextrin (C-CD), encapsulated curcumin extract with maltodextrin (C-MD), encapsulated tomato extract with β-cyclodextrin (T-CD) and encapsulated tomato extract with maltodextrin (T-MD) were tested to confirm their formation by (UV-Vis.) spectroscopic analysis.
RE showed a maximum absorbance at 550 nm while R-CD, and R-MD presented a maximum absorbance peak at 540 nm and 550 nm, respectively, this shifting indicated the success of encapsulation process.
GE showed maximum absorbance at 280 nm, while G-CD and G- MD presented a shifting to 278 nm and 297 nm, respectively referring
that the encapsulation process was completed.
CE presented maximum absorbance at 427 nm, while C-CD and C-MD presented a shifting to 421 nm which considered evidence on the completion of encapsulation processed showed a maximum absorbance at 257 nm while T-CD, and T-MD presented a maximum absorbance peak at 255nm and 262 nm, respectively, a clear shifting also indicated the formation of the encapsulated forms of tomato extract.
5.2 Physical properties of the prepared complexes
• Solubility
The main problem that restricts the benefiting from curcumin is its low solubility, encapsulation process improved its solubility as concluded from the obtained data where the solubility was increased from 38.88% in CE to 98.22% and 96.35 % in T-CD and T-MD respectively.
• Hygroscopicity
Hygroscopicity values of R-CD and R-MD are 18.28 and 17.66 (g/ 100g D.W) respectively, and the moisture content was 7.91% and 8.91%. G-CD and G-MD showed hygroscopicity values 4.87(g/100g D.W) and 11.84 (g/ 100g D.W) respectively and moisture content 2.13 % and 3.66 %. C-CD and C-MD presented hygroscopicity values 4.01(g/ 100g D.W) and 11.87(g/ 100g D.W) and moisture content 2.54% and 5.2
%. Finally T-CD and T-MD presented hygroscopicity values 7.41 and
13.5 (g/ 100g D.W) and moisture content 5.84% and 6.875, respectively.
5.3 Bioactive Components
• Total phenolic content (TPC) and Total flavonoid content (TFC)
All the prepared samples before and after encapsulation had a significant content of phenols and flavonoids. Total phenolic content in G-CD was 49.81 mg GAE /100 g DW, it was clearly increased comparing with GE which contained 43.61 mg GAE /100 g DW, and the total
flavonoid content was increased also from 25.64 mg QE /100 g DW in GE to 31.85 mg QE /100 g DM in G-MD. For TE, T-CD and T-MD; TPC
was 53.39, 72.4 and 88.71 mg GAE /100 g DW but, TFC was 5.76 10.69 and 14.34 mg QE /100 g DW with a remarkably increase in both TPC and TFC after encapsulation comparing with TE.
• Recovery index of TPC and TFC after encapsulation
The impact of encapsulation on enhancement of the TPC and TFC could be detected by calculating the recovery index for both TPC and TFC. The recovery index for R-CD and R-MD was 86.96% and 52.30% for TPC, and 83.5and 54.7 for TFC, respectively, while in G-CD and G- MD was 114.21% and 84.63% for TPC and 87.75% and 124 % for TFC, respectively. C-CD and C-MD on the contrary showed lower recovery index than in the other prepared complexes it was 8.51 % and 10.7 % for TPC and 7.6 % and 8.58 % for TFC, respectively. The recovery index of Tomato encapsulated extracts (T-CD and T-MD) was 135.6 % and 166.2
% for TPC and 158.6 % and 284.9 % for TFC with a remarkable increasing.
5.4 Antioxidant activity
• Radical scavenging activity (%ARA)
The presence of TPC and TFC, in addition to another bioactive compounds indicates potential antioxidant activities. % ARA is one of the most popular and applied features to reflect the antioxidant capacity of the prepared samples. The obtained data revealed that encapsulation process by freeze drying had a significant impact on increasing %ARA. In RE, R- CD and R-MD the % ARA was 72.38 %, 78.62 % and 79.62 %
respectively. The %ARA values in GE, G-CD and G-MD were 50.45%, 43.93% and 38.01%, respectively. CE, C-CD and C-MD presented high
%ARA values; 50.11%, 52.37% and 46.44% respectively. TE, T-CD and T-MD exhibited ARA% values 78.07 %, 80 % and 78.88 % respectively.
TE, T-CD and T-MD exhibited % ARA values 78.07 %, 80 % and 78.88
% respectively.
The Retained activity (%) of ARA for R-CD and R-MD was
108.62 % and 110 % while, for G-CD and G-MD was 87.07 % and 75.34
% , but in C-CD and C-MD was 104.51 % and 92.67 % finally, it was
102.5 % and 101 % for T-CD and T-MD respectively.
• Reducing power activity and Total antioxidant capacity (TAOC)
RP and TAOC are the other features that reflect the antioxidant capacity. G-CD and G-MD exhibited significant increase in % RP 1.025 and 1.04 µg/ml as ascorbic acid, respectively comparing with GE (0.93 µg/ml as Ascorbic Acid). However, the TAOC for G-CD and G-MD were lower than its value for GE, there is no significant deference (P≤0.05) between GE and G-MD.
C-MD had a higher effect on %RP (3.51µg/ml as ascorbic acid) than C-CD (2.95 µg/ml as Ascorbic Acid) and CE (2.89 µg/ml as ascorbic acid).% RP increased from 0.93 µg/ml as ascorbic acid in TE to1.01and
1.22 µg/ml as ascorbic acid in T-CD and T-MD respectively. The TAOC also was increased because of protective effect of bioactive component by encapsulation of tomato extract, it was 32.67 µg/ml as Ascorbic Acid in TE and increased to 37.33 µg/ml as ascorbic acid in T-CD. Encapsulation of the prepared samples with CD or MD increased both RP and TAOC for most of the samples.
(%RP) of red cabbage extract RE was increased from 2.49 (µg/ml as ascorbic acid) to 2.66 and 3.85 (µg/ml as ascorbic acid) for R-CD and R-MD respectively, also TAOC in R-CD was increased to 32.32 (µg/ml as ascorbic acid) comparing with RE which exhibited lower TAOC value (27.92 µg/ml as ascorbic acid). However, R-MD was closer to RE in TAOC assay (25.75 µg/ml as ascorbic acid).
The Retained activity of both RP and TAOC were determined to detect the increasing effect of encapsulation process to improve them. Retained activity (%) of Reducing Power of R-CD and R-MD was 106.5
% and 110. % while, for G-CD and G-MD was 110.22 % and 111.83 %, but in C-CD and C-MD was 102.08 % and 121.45 % finally, it was 109.2
% and 131.7 % for T-CD and T-MD, respectively.
Retained activity (%) of Total Antioxidant Capacity of R-CD and R-MD was 115.8 % and 92.3 % while, for G-CD and G-MD was 93.61 % and 99.22 %, but in C-CD and C-MD was 98.91 % and 82.2 % finally, it was 114.3 % and 99.3 % for T-CD and T-MD, respectively.
5.5 Stability of encapsulated plant extracts
• Stability assay of encapsulated plant extracts against pH values
The stability of all the prepared samples were examined against four different pH degrees. The encapsulation of the prepared plant extracts improved their stability and decreased their degradation. The degradation of RE at pH 9 after 3 hours was 30.6 % but it decreased in R- CD to 16.33%. The degradation of RE at pH 7 was decreased from 4.42
% in RE to 2.34 % in R-MD.
At pH 5, the degradation (%) of GE was 91.56 % while in G-CD was 21.88% and 1.54 % in G-MD after three hours of the treatment .At pH 7 the degradation of CE was 21.47 % after 3 hours of treatment while in C-CD and C-MD it decreased to 7.48 % and 8 % respectively, also at pH 9 the degradation decreased from 51.83% in CE to 31.33% in C-CD and 19.75 % in C-MD. At pH 3, the degradation (%) of TE was 6.05 % after 3 hours of treatment while in T-MD was 2.36 %. The degradation values of TE, T-CD and T-MD at pH5 were 4.65 %, 1.92 % and 2.3 %, respectively.
• Thermal stability of encapsulated plant extracts by Differential Scanning Calorimetry (DSC)
The DSC method reflects the thermal behavior of samples during analysis. The DSC curves of all the prepared samples introduced an improvement of their thermal stability and a confirmation on their complete formation. DSC curve of pure β-CD produced an endothermic peak at about 107.33 ˚C while, the DSC curve of MD produced an endothermic peak at 85.09 ˚C, and two other peaks at 264 οC and 307 οC.
DSC curve of RE presented a characteristic peak at 115 ˚C while the peak was shifted to higher temperature (121.52 ˚C) in R-CD and the endothermic peak of β-CD was absent. In R-MD a shifting to 128 ˚C and
222.65 ˚C was appeared referring to an increase in their thermal stability in addition to confirming their formation. DSC curve of GE presented two characteristic endothermic peaks at 28.88 ˚C and 32.61 ˚C while G-CD exhibited an absorption peaks at 132.95 ˚C and 346.06 ˚C in addition to absence of the characteristic peak of 6-gigerol indicating the formation of G-CD and G-MD and improvement of their thermal stability.
The DSC curve of G-MD exhibited three peaks at 163.35 ˚C,
214.26 ˚C and 319.43 οC showing a clear shifting in addition to absence of the characteristic peak of 6-gingerol.
The thermogram of CE presented three peaks at 71.25 ˚C, 91.80 ˚C and 97.12 ˚C but, in DSC thermogram of C-CD two peaks were appeared at 92.03 ˚C and 328 ˚C with absence of both CD endothermic peaks and curcumin characteristic peaks confirming the formation of C-CD and the enhancement of its thermal stability. DSC thermogram of C-MD presented a clear shifting for characteristic peaks of curcumin and absence of endothermic peaks of MD which confirm the formation of C- MD and refer to an increase of its thermal stability.
DSC thermograms of TE presented two characteristic peaks at
94.75 ˚C and 103 ˚C. A shifting to higher temperature (136.95 ˚C and 146 ˚C) was appeared in T-CD in addition to absence of the characteristic
endothermic peak of β-CD. T-MD also introduced shifting to higher temperature (125.87 ˚C, 135.77 ˚C ,142 ˚C and 182.56 ˚C) in addition to absence of the characteristic endothermic peak of MD confirming the formation of T-CD and T-MD and improvement in their thermal stability.
5.6 Stability of the encapsulated plant extracts against in-vitro gastro- intestinal digestion.
• TPC before and after in-vitro gastro-intestinal digestion
A reasonable amount of TPC and TFC of the encapsulated plant extracts were remained after in-vitro gastro-intestinal digestion and were detected also by calculating their recovery index, referring to their stability against digestion conditions then there are ready to be absorbed by small intestines’ in RE, R-CD and R-MD was 20.48, 17.81and 10.9 mg GAE /100 g DW respectively before digestion, while it decreased to 4.67, 6.6 and 2.89 mg GAE /100 g DW after digestion. TPC of G-CD was
49.8 mg GAE /100 g DW before digestion and decreased to 32.8mg GAE
/100 g DW after digestion. TPC in C-MD was 662.5 mg GAE /100 g DW before digestion and decreased to 407.6 mg GAE /100 g DW after digestion. TPC in T-CD was 72.4 mg GAE /100 g DW before digestion and decreased to 43.12 mg GAE /100 g DW after digestion.
• The Recovery Index (%) of total Phenols after simulated gastrointestinal digestion.
The Recovery Index (%) of total Phenols after simulated gastrointestinal digestion for R-CD and R-MD was 37.1 % and 36.5 % while, for G-CD and G-MD was 65.8 % and 61.9 %, but in C-CD and C- MD was 58.38 % and 61.5 % finally, it was 59.5 % and 60.34 % for T- CD and T-MD, respectively.
• The radical scavenging activity (ARA%) before and after in- vitro gastro-intestinal digestion
The ARE% in RE, R-CD and R-MD was 72.38 %, 76.8 % and
77.37 %, respectively before digestion, while it decreased to 26.8 %, 26.3
% and 25.6 % after digestion. The ARE% in GE, G-CD and G-MD was
38.01 %, 43.9% and 50.22% respectively before digestion, while it decreased to 6.03%, 6.9% and 6.02% after digestion. The % ARE in CE, C-CD and C-MD was 43.59%, 52.04% and 47.6 % respectively before digestion, while it decreased to 9.9%, 15.3 % and 12.2% after digestion.
The ARE % in TE, T-CD and T-MD was 78.06%, 80% and 78.63% respectively before digestion, while it decreased to 9.9%, 11.6 % and 10.4% after digestion.
In general in-vitro gastro-intestinal digestion led to decrease in bioactive compounds of plant extracts. The results showed a decrease in rate of loss in total phenol in encapsulated plant extracts after digestion. This is due to the protective effect in bioactive component by encapsulation process.
5.7 Conclusion
The use of natural plant sources is an important and useful trend, where, it has several important effects such as an antioxidant and their multiple therapeutic effects. This due to fact that it contains many biologically active compounds such as phenolic compounds, flavonoids, alkaloids, vitamins and sterols etc..
In this study, eight complexes were produced from four natural plant extracts (Tomato, Red Cabbage, Ginger and Turmeric) by immobilizing them on two types of carriers (ß-cyclodextrin or maltodextrin) by Freeze drying process (Encapsulation) which is considered an important processes for improving the properties and the stability of bioactive compounds. The obtained data were:
5.7.1 Encapsulation of Red Cabbage:
** Improved the bioavailability of bioactive compounds.
** Decreased the degradation of bioactive components on all pH values compared with plant extract.
** Increased the percentage of radical scavenging activity
5.7.2 Encapsulation of Ginger Extract :
** Improved the capacity of antioxidant .
** Improved thermal stability and availability of bioactive components, and also decreased its degradation (%) on high pH conditions compared with ginger extract
5.7.3 Encapsulation of Curcumin Extract:
** Improved the solubility of curcumin extract significantly, as low solubility is considered one of the most important problems of benefiting from it and from other bioactive compounds.
5.7.4 The Encapsulation of Tomato Extract:
** Improved the bioavailability of bioactive compounds.
** Decreased the degradation of bioactive components on all pH values compared with plant extract.
** Increased the percentage of radical scavenging activity.