PHYTOCHEMICAL SCREENING, TOTAL POLYPHENOLS AND FLAVONOIDS CONTENT AND ANTIRADICAL ACTIVITY OF METHANOLIC EXTRACT OF ANNICKIA CHLORANTHA FROM GABON

In traditional medicine, Annnickia chlorantha (Annonaceae)is used in many parts of Africa to treat several pathologies. It is used for the management of stomach problems, for the treatment of jaundice, tuberculosis, urinary tract infections, malaria, hepatitis and ulcers forms, for gallstones or even diarrhea. The phytochemical analysis and determination of the antiradical activity of the methanolic extract of the trunk bark from Annickia chlorantha from Gabon was the subject of this study. Phytochemical screening revealed the abundance of alkaloids, polyphenols and catechics tannins.The total polyphenol content released by the Folin-Ciocalteu method was 309.17 ± 38.05 g of gallic acid equivalent per 100 mg of dry matterand the total flavonoids content performed with AlCl 3 was 155.16 ± 21.06 g of quercetin equivalent per 100 mg of dry matter. The antiradical activity was limited to 81.58% ± 1.25 without disappearance of the ABTS • + radical after 6 minutes of incubation. These results confirm the correlation between the polyphenol content and the antiradical activity.

In traditional medicine, Annnickia chlorantha (Annonaceae)is used in many parts of Africa to treat several pathologies. It is used for the management of stomach problems, for the treatment of jaundice, tuberculosis, urinary tract infections, malaria, hepatitis and ulcers forms, for gallstones or even diarrhea. The phytochemical analysis and determination of the antiradical activity of the methanolic extract of the trunk bark from Annickia chlorantha from Gabon was the subject of this study. Phytochemical screening revealed the abundance of alkaloids, polyphenols and catechics tannins.The total polyphenol content released by the Folin-Ciocalteu method was 309.17 ± 38.05 g of gallic acid equivalent per 100 mg of dry matterand the total flavonoids content performed with AlCl 3 was 155.16 ± 21.06 g of quercetin equivalent per 100 mg of dry matter. The antiradical activity was limited to 81.58% ± 1.25 without disappearance of the ABTS •+ radical after 6 minutes of incubation. These results confirm the correlation between the polyphenol content and the antiradical activity.  (Karmakar et al., 2011). In order to help and protect populations, it is necessary to study the properties of commonly used medicinal plants. It is with this in mind that our work has focused on the chemical screening and evaluation of the antiradical activity of the methanolic extract of Annickia chlorantha (Annonaceae). This plant is used for its therapeutic properties, in particular in the treatment of malaria, fever growth, typhoid fever and hepatic infections as some forms of ulcers

Material Et Methods:-Plant material:
The trunk bark of Annickia chlorantha was collected in august2018between Oyane 4 and FourPlace in EstuaireProvincial. The fresh trunk bark was dried for about fifteen days protected from light in an air-conditioned room. It was powdered using an electric grinder (Flour Mills Nigeria, El MOTOR N o 1827). The resulting powder was stored at room temperature in a clear labeled packaging bag.The plant has been identified in the National Herbarium of Gabon.

Preparation of methanolicextract:
200 ml of methanol were added to 10 g of powder contained in an Erlenmeyer flask with a magnetic bar. After hermetically closing the Erlenmeyer flask, the mixture is left under magnetic stirring for 24 hours and then filtered using Whatman N o 1 filter paper. The filtrate was stored at 4°C until analysis.

Qualitative Phytochemical analysis:
Phytochemical screening of dry extracts was achieved through simple methods as described inCiulei, 1964 and Harborne, 1998.

Determination of Total polyphenolscontent:
The evaluation of the total polyphenols was carried out by the Folin-Ciocalteu method described by Singleton et al. (1999) and modified by MefouetAbessolo et al. (2021) on methanolic extract. Gallic acid was used as a standard to establish the standard range (0-150 mg/l). The results are expressed in mg of Gallic Acid Equivalent (QE) per 100 g of dry extract.

Determination of Total flavonoidscontent:
The total flavonoids are determined according to the method of Arvouet-Grant (1994) with some modifications. Quercetin was used as a standard to establish the standard range (0-50 mg/l). Results are expressed in mg of quercetin equivalent (QE) per 100 g of dry extract.

Evaluation of antiradical activity:
Antiradical activity was determined by the ABTS method (Re et al., 1999). The antiradical activity of methanolic extract is deduced from its ability to inhibit ABTS •+ compared to a reference antioxidant (gallic acid).The ABTS •+ radical ion is obtained by reacting the ABTS molecule (7 mM) with potassium persulfate (2.45 mM) in distilled water for 16 hours at room temperature and in sunlight. The ABTS •+ solution obtained is diluted with sodium phosphate buffer (5 mM, pH = 7.4), in order to obtain a stock solution having an initial absorbance value of between 0.65 and 0.70 at 734 nm (UV spectrophotometer).

Results And Discussion:-Phytochemical screening:
The phytochemical tests carried out on methanolic extract of trunk bark of Annickia chlorantha show the abundance presence of alkaloids, catechics tannins and polyphenols. There's also reducing compounds, flavonoids (flavones), sterols and coumarins ( Table 1) According tannins catechics, studies reveal antibacterial and antiviral activities with capacities to reduce blood pressure (Bele et al., 2010;Coșarcă et al., 2019). The presence of these important bioactive compounds indicates the medicinal value of Annickia chlorantha and could be at the origin of various activities revealed by the population and traditional healers.

Total Phenolic and Flavonoid contents:
The total phenol content was determined in comparison with a standard which is gallic acid. The Results (Table 2) were expressed in milligrams of gallic acid per 100 grams of dry matter (mg GAE/100 g DM), using the linear equation extract: Y = 0,011X + 0,0291 (with R² = 0,9972). Thus, total phenolic content is 309,18 ± 38,06 mg GAE/100 g DM.
The total flavonoid content was determined in comparison with quercetin.Results were expressed in milligram equivalent of quercetin per 100 grams of dry matter (mg EQ/100g DM. using the linear equation Y = 0.0258X + 0.043 (with R 2 = 0.9973). Thus, total flavonoids content is 155,16± 21,06mg QE/100 g DM. In Nigeria, Olanlokun and Akomolafe (2013) showed that the methanolic extract has a high content of total polyphenols (838.03 ± 34.40 mg GAE/g of extract) and an appreciable content of total flavonoids (140 ± 0.008 mg QE/g of extract). In Cameroon, Djimeli et al. (2017) obtained a total polyphenol content of 690.53 ± 23.597 mg GAE/g of extract. In view of these results, the stem bark of Annickia chlorantha from Nigeria and Cameroon are more rich ontotal polyphenolsthanthe trunk bark of Annickia chlorantha from Gabon.However, the trunk bark of the Gabonese plant contains more total flavonoids.

Antiradical activity:
The antiradical activities of gallic acid and methanolic extract from the trunk bark of Annickia chlorantha were reported in Figures 1 and 2.
For the gallic acid (Figure 1), the percentage of the antiradical activity increases with the concentration after 6 minutes of incubation. The antiradical activity reaches 100% after 6 minutes of incubation for concentrations greater than or equal to 0.84 μg/ml. However, regarding the methanolic extract, the anti-radical activity was limited to 81.58% ± 1.25 without disappearance of the ABTS •+ radical after 6 minutes of incubation ( Figure 2).  According absence of disappearance of ABTS, we can deduce that the methanolic extract of the bark of Annickia chlorantha has no antioxidant activity or that it's very weak. This result could be explained by the low contents of polyphenols and total flavonoids obtained.

Conclusion:-
This study is the first carried out on Annickia chlorantha from Gabon. Through this study, the phytochemical composition of the methanolic extract of the trunk bark. revealed thepresence of alkaloids, catechics tannins, reducing compounds, flavonoids (flavones), sterols and coumarins. These compounds can explain the use of this