Chemical Analysis, Phenolic Content, and Antioxidant Activities of Aqueous and Organic Moroccan Juglans regia L. Bark Extracts

Abstract

Background: The present study was conducted on the Moroccan Juglans regia L. bark, in comparison with other Juglans regia collected in other countries, to study the effects of the use of different extraction solvents (water, ethanol, acetone, and diethyl ether), aqueous and organic extraction method, hot and cold extraction by maceration modalities on the presence and content of the different phytochemicals, and on the antioxidant activity. Methods: Various solvents of increasing polarity were used for the preparation of aqueous and organic extracts. Afterwards, a phytochemical screening, an estimation of phenolic compounds, flavonoids, and tannins contents was conducted. The in vitro antioxidant activity was carried out by five tests: H2O2, ABTS, FRAP, DPPH, and reducing power. Subsequently, Principal Component Analysis (PCA) was used to establish the correlation between phenol content and antioxidant activity. Results: Phytochemical analysis showed that the 9 extracts prepared are characterized by the presence of flavonoids, catechic tannins, saponins, anthraquinones, and quinones, and that the macerated acetone extract contains the highest content of phenolic compounds (327.972±0.06 μgEAG/mgE), flavonoids (1267.981±2.911 μgEQ/mgE), and tannins (38.056±1.886 μgEC/gE). The best antioxidant activity was obtained with the macerated acetone which was found to be the most active via the five different tests, with a percentage of scavenging of H2O2 equal at 24.13±1.81, a higher value of ABTS equal to 602.29±0.34 μgET/mgE. PCA allowed us to deduce that phenolic compounds, flavonoids, and tannins are strongly correlated with antioxidant activity. Conclusion: Moroccan Juglans regia may be one of the potential sources of antioxidant compounds.