The objective of this study was to optimize the extraction conditions of antioxidant and antihyperglycemic properties of Boscia Senegalensis decoction using response surface methodology. A Central Composite Design was performed to determine the effect of powder to water ratio (range 0.3/10 - 4/10 g/mL), extraction time (range 3 - 38 min) and extraction temperature (range 25 - 95°C) on total polyphenol content, DPPH free radical scavenging, Ferric ion-reducing power and glycemic index of decoction. Desirability function was established to achieve the best possible combination of factors to a maximum value of total phenolic content, DPPH free radical scavenging, total reducing power of the decoction and a low level of glycemic index. The results revealed that the variation of all the response variables as a function of the factors fit very well the quadratic model with adjusted R2 varying from 82 to 93%. The range variation observed were: Total polyphenol content 0.47 to 2.04 mg galliceq/100mL, glycemic index 55.1 - 89.6%, DPPH antiradical scavenging activity 30.2 - 67.2%, Ferric ion-reducing power 0.29 - 0.95 mg vitamin C eq/100mL decoction. The highest variation of responses 38% was observed on the phenolic content while the lowest 12% was observed on the glycemic index. Significant linear correlation (r = -0.90; p<0.01) was observed between the total polyphenol content and the glycemic index of the decoction. Computed desirability function estimated with accuracy the optimal conditions at 55°C extraction temperature, 3/10 g/mL powder to water ratio and 10 min extraction time. At this optimum point the polyphenol content, total reducing power, DPPH free radical scavenging and glycemic index were respectively 2.34 mg galliceq/100 mL, 0.41 mg vitamin C eq/100 mL, 59.0% and 51.6%. In conclusion the response surface methodology successfully conducted to production of decoction of Boscia Senegalensiswith the highest polyphenol content, antioxidant properties and the lowest glycemic index.
Belonging to the Capparidaceae family, Boscia Senegalensis is a wild plant which largely grows under the 20th parallel of the soudanian area of Africa from Senegal, through the Northern Burkina Faso, Nigerian and Niger border, the southern lake of Chad and ended in the Western Sudan. It is an evergreen under shrub plant, usually 1 to 2 m mean height . Largely called in these regions as “Buldumhi” in Fulfulde and “Ndandam” in Wolof , Boscia plant produces acidic fruits that are commercialized either for human nutrition or for medicine. The fruits are usually soaked in water for some days to a week to remove the acidity before consumption. The utilization of Boscia seeds for food is generally limited in rural households, notably in Burkina Faso, where populations experienced a food shortage period occurring early in the rainy season and lasting until the next crop harvest period. Rather, Boscia seeds are mostly used for their medicinal properties. In Chad, for instance the seeds are regularly used traditionally for the treatment of diabetes and associate diseases including obesity and coronary heart diseases . One active principle in Boscia has been identified as a glucocapparin, a sulfonated glucose which exhibited not only hypoglycemic effect, but also cytotoxicity . It is demonstrated that Boscia is rich in phenols and antioxidant properties , and these molecules may also justify the use of Boscia in traditional medicine. Traditionally the decoction used in patient treatment consisted of mixing the seed powder (about 200 g) with water (about 1L) followed by boiling for about 30 min. However the conditions under which Boscia decoctions are prepared varied from one healer to another and the optimal condition to achieve the extraction of active principle is unknown and need to be investigated.
Optimization of aqueous extraction of plant material has been widely investigated on several food materials including dry seeds, herbs, etc., Generally the most important factors are extraction time and temperature, powder mass to water volume ratio. In particular the extraction of phenolic compounds and antioxidant principles from plant materials has been shown to depend on such factors, but the global and interaction effects of these factors may depend on the type of matrix and this has not yet been investigated on Boscia powder.
The general objective of the present work was to determine the conditions of aqueous extract production with optimal hypoglycemic effect. More specifically the effect of extraction time, temperature and water to flour ratio on total phenolic compounds, antioxidant and hypoglycemic properties of Boscia was first studied, and the determination of optimal extraction condition using multiresponse optimization methodology was done.
|Run||Independent variables||Dependent variables|
|Coded and actual level|
|Temperature(°C)||Time(min)||Ratio(g/mL)||DPPH free Scavenging(%)||Total reducing power(Eq mg VitC/ 100 mL of extract)||Total phenolics content(Eq mg gallic acid/100 mL of extract)||Glycemic index(%)|
|1||-1 (40)||-1 (10)||-1 (1/10)||45.433||0.348||1.127||67.95|
|2||1 (80)||-1 (10)||-1 (1/10)||49.557||0.693||1.468||62.27|
|3||-1 (40)||1 (30)||-1 (1/10)||32.933||0.705||1.598||66.26|
|4||1(80)||1 (30)||-1 (1/10)||48.905||0.702||1.161||76.68|
|5||-1 (40)||-1 (10)||1 (3/10)||46.862||0.598||1.224||72.62|
|6||1 (80)||-1 (10)||1 (3/10)||64.862||0.952||1.273||68.52|
|7||-1 (40)||1 (30)||1 (3/10)||39.823||0.466||0.853||76.35|
|8||1 (80)||1 (30)||1 (3/10)||67.215||0.411||0.467||89.63|
|9||-1,73 (25)||0 (20)||0 (2/10)||30.215||0.291||1.159||79.26|
|10||1.73 (95)||0 (20)||0 (2/10)||56.443||0.595||0.621||86.19|
|11||0 (60)||-1.73 (3)||0 (2/10)||48.861||0.748||1.853||64.72|
|12||0 (60)||1.73 (38)||0 (2/10)||41.911||0.768||0.687||81.44|
|13||0 (60)||0 (20)||-1.73 (0.3/10)||48.518||0.637||2.041||55.09|
|14||0 (60)||0 (20)||1.73 (4/10)||63.131||0.361||1.294||69.72|
|15||0 (60)||0 (20)||0 (2/10)||32.733||0.414||0.692||83.47|
|16||0 (60)||0 (20)||0 (2/10)||50.395||0.484||0.847||79.66|
|17||0 (60)||0 (20)||0 (2/10)||38.066||0.510||0.882||78.30|
Table 1: Matrice of central composite design of independent variables (actual and coded levels) for extraction of antioxidant properties of Boscia Senegalensis flour.
|Source||DPPH Free Scavenging (%)||Reducing power (mg Vit C eq/100mL)||Total phenolics (mg galliceq/100mL)||Glycemic index (%)|
|DF||Coefficients||Sum of squares||F-ratio||P-value||Coefficients||Sum of squares||F-ratio||P-value||Coefficients||Sum of squares||F-ratio||P-value||Coefficients||Sum of squares||F-ratio||P-value|
|Lack of ?t||5||11.34||0.03||0.998||0.034||2.74||0.288||0.260||5.10||0.172||0.191||1.00|
|Parameters||Predicted values||Experimental values|
|Phenols content (Eq mg gallic acid/100 mL of extract)||2.02||1.98±0.05|
|Glycemic index (%)||54.71||50.20±2.25|
|Total reducing power ((Eq mg Vit C/ 100 mL of extract)||0.34||0.28±0.04|
|DPPH free radical scavenging (%)||62.02||60.12±0.15|
Table 4: Predicted responses at optimum conditions.
Mean ± SD, n = 3
Phenolic compounds can be defined as any compound containing a benzene ring with one or more hydroxyl groups . It has already been admitted that these compounds possess antioxidant and hypoglycemic activities . The extraction procedure of phenolics in plant materials has been reviewed by Khoddami et al., . Among solvent usually employed for phenolic extraction, water has been shown to be efficient in extracting phenolic compound , flavonoids and proanthocyanidins. We showed in this study that the yield of extraction of phenolic compounds depended on extractions conditions such as the temperature, the time and the ratio of powder to solvent. According to some authors longer extraction time increase the chance of oxidation of phenolic unless reduction agent are added to the solvent .However, some authors reported longer time as 30-120 min as optimal extraction time of polyphenolics [17,18]. The increase in phenol extraction with increase in temperature has also been reported in other food materials  and may be a consequence of increase in agitation which not only increases the diffusivity of solvent into granules, but also the mass transfer and solubility of molecules. We observed in this study a decrease of phenolic extraction at higher temperature which may result from their loss by volatilization and thermal, chemical and enzymatic decomposition , or by complexation with other compounds such as protein which remain bound to the matrix and subsequent insolubilisation . But this may depend on the type of phenols as is the case of stems the optimal time and temperature was observed for 270 min and 55°C . As for the effect of solvent to sample ratio, basically its increase promotes phenolic extraction, but it is advised to determine the optimum ratio so as to minimize the solvent input and saturation effects .
The rate of extraction of phenolic may impact the in vivo and in vitro activities of the decoction as they might be active principles as reported for other plants resources . Fortunately we found in this study a significant (r = - 0.93; p<0.001) and linear relationship between the total phenols content and the glycemic index. The negative correlation implied that as the phenols content increased in the decoction, the glycemic index decreased. This indeed highlighted the role of phenols in the hypoglycemic activity of Boscia decoction claimed by consumers and healers. Mahamat et al.,  recently reported a sugar complex, glucocapparin, as the active molecule in Boscia decoction. Although this may not be rejected, it comes from this study that phenols may partly play a role either alone or in interaction with other hydrophilic compounds such as polysaccharides . One major mechanism by which phenols might regulate glucose concentration was reported in the intestine through inhibition of the membrane transport Na+ - dependent D-glucose . In this respect dietary phenolic compound favor the dissipation of the Na+ electrochemical gradient which provides the driving force for active glucose accumulation .
Generally the glycemic index increased with increase in extraction time and temperature, suggesting that higher extraction time and temperature had detrimental effects on the biological activity of the decoction.
Another beneficial aspect of dietary phenols is their antioxidant activity in biological systems. Recent studies on the antioxidant activity of Boscia demonstrated their high antioxidant activity potential . Unfortunately we did not found significant correlation between the phenols and neither the DPPH scavenging activity (r = - 0.17) or the total reducing power (r = 0.11). In addition no significant linear relation was observed between the DPPH scavenging activity and the total reducing power of the Boscia decoction. This may be a result of thermal degradation of Boscia phenols at higher temperature as significant decrease in phenol was observed at temperature higher than 70°C. In addition other components such as polysaccharides in the aqueous extract may be responsible of the activity , and this needs to be investigated.
The conditions for production of aqueous extract with high phenols content and low glycemic index were determined 10 min and 55°C. In these conditions our decoction contained 2.02 mg phenols/L of decoction, exhibited about 62% scavenging activity. The glycemic index of the decoction was lower than 55, meaning our Boscia decoction may be classified as low glycemic index potential as compared to intermediate (55-69) and high (70 -100) glycemic potential molecules . All these values give our Boscia decoction a high potential to contribute to the management of diabetes and associated metabolic disorders.
The extraction conditions have significant effects on the antioxidant and hypoglycemic properties of Boscia Senegalensis decoction, but the behavior varied from one response variable to another. While the DPPH activity do not varied significantly with any of the studied factor, the total reducing power increases significantly in a quadratic manner with increase in the extraction time and temperature. In addition the total phenolic content linearly decreases with the increase in extraction time and powder to water ratio concomitantly with an increase in glycemic index. Globally decoction with high total phenolic content exhibits low glycemic index thus suggesting a potential role of Boscia phenol in the management of diabetes. With a desirability of 90%, the optimal condition to maximize the phenol, DPPH antiradical scavenging activity and total reducing power, and to minimize the glycemic index is 55°Cextraction temperature, 3/10 g/mL powder to water ratio and 10 min extraction time. In these conditions, the Boscia Senegalensis extract is expected to exhibit higher biological activity. However the functionality of the decoction will depend on the dose and in this respect the toxicity as well as the glucosinolate content of the Boscia extract need to be investigated. In addition, study of the biological activity of the extract including antioxidant activity, α and β glucosidase inhibition and effect on the blood biochemical components needs to be investigated. Investigations on the antioxidant and hypoglycemic effect of isolate molecules in the aqueous extract of Boscia are also needed.
Citation: Faustin D, Selestin SD, Nicolas NY (2017) Aqueous Extraction Optimization of the Antioxidant and Antihyperglycemic Components of Boscia Senegalensis Using Central Composite Design Methodology. J Food Sci Nutr 3: 015.
Copyright: © 2017 Dongmo Faustin, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.