Comparative Study of the Effect of Two Extraction Solvents on Polyphenols Content and Antioxidant Activity of Alstonia Boonei Bark

Abstract

Oxidative stress (OS) is the imbalance between the generation of reactive oxygen species (ROS) and the body's antioxidant defenses in favor of ROS. ROS are chemical species that can be neutralized by natural phytochemicals like phenolic compounds present in medicinal plants and whose extraction depends on the solvent system used. Thus, the present study aimed to evaluate the effect of two extraction solvents on the polyphenols content and antioxidant activity of Alstonia boonei barks. For this, the bark of A. boonei were harvested, processed, dried and ground, then the powder was macerated in two solvent systems (water and water-ethanol). Subsequently, the quantitative phytochemical analysis of the different extractions was done by evaluating total polyphenols content (TPC), total flavonoids content (TFC) and alkaloids; followed by an in vitro evaluation of the antioxidants activity through radicals scavenging (DPPH and NO.) and the reducing power of ferric iron to ferrous iron. The relationship between antioxidant potential (DPPH, NO and FRAP) and polyphenols (total polyphenols and total flavonoids) was investigated using simple linear regression. It appears that the aqueous extract allowed better extraction of phenolic compounds from A. boonei bark; and exhibited better antioxidant activity. In addition, a strong correlation (r and R2) was found between polyphenols (TPC and TFC) and antioxidant activity (DPPH, NO and FRAPP). Thus, we preferably recommend the use of water as a solvent for traditional preparations of A. Boonei bark extract for therapeutic purposes.