Evaluation of the antioxidant activity of certain extracts from the leaves of Phlomis crinita Cav from North western Algeria

The Phlomis crinita Cav., a widely distributed Lamiaceae in northwestern Algeria, possesses numerous therapeutic virtues. The objective of this study is to evaluate the antioxidant properties of the leaves of this species by comparing them to ascorbic acid using the DPPH (2,2-diphenyl-1-picrylhydrazyl) method. The assessment of antioxidant properties of extracts obtained through reflux, including chloroform, n-butanol, and ethyl acetate, revealed a highly significant activity with IC 50 values comparable to that of ascorbic acid (reference), especially for the chloroform extract. These results may be attributed to polyphenols, particularly tannins and flavonoids. It would be interesting to quantify them and determine if there is a correlation between their content and the intensity of this activity.


Introduction
Phlomis crinita Cav. is a lamiaceae that is widespread in north-western Algeria and has many therapeutic properties.The aim of this study was to evaluate the antioxidant properties of the leaves of this species by comparing them with ascorbic acid using the DPPH (2,2-diphenyl-1-picrylhydrazyl) method [1,2].

Plant material
In January, the sample is collected in the Oued el Fodda region in Chlef at an altitude of 830 meters, at 36° 10' 59" North, 1° 31' 59" East, located in the Northwest of Algeria [1,3].
The leaves (approximately 500 grams) are left to dry for several weeks in a thin layer, in the shade, at room temperature, in a dry and well-ventilated place until complete desiccation.They are stored in paper bags, protected from light, moisture, and dust, until they are used [1,3].

Preparation of different extract
5 grams of plant material are refluxed using a methanol-distilled water mixture (70v/30v) for 1 hour.After filtration and subsequent evaporation of the solution to dryness, the residue is macerated in distilled water for 24 hours.Delipidation is carried out with n-hexane, followed by successive extractions using solvents of increasing polarity (in a separatory funnel) with chloroform, ethyl acetate, and n-butanol, using volumes of 3 x 50 ml for each solvent.The chloroform, ethyl acetate, and n-butanol extracts are evaporated to dryness at 44 °C, weighed, and reconstituted in methanol [4,5].
Into dry tubes, a volume of 1 ml of each dilution was introduced, plus 1 ml of 0.004% DPPH (2,2-Diphenyl-1picrylhydrazyl) methanoic solution, followed by vortexing.The tubes were placed in the dark at room temperature for 30 min.The reading was carried out by measuring the absorbance at 517 nm by a spectrophotometer.A blank (negative control) was prepared and composed of 1 ml of methanol and 1 ml of DPPH (0.004%).For each dilution, the experiment was repeated three times [6,7].

Results
The antioxidant activities of the extracts obtained through reflux (chloroform, ethyl acetate, n-butanol) and ascorbic acid (reference) are depicted in Figures 1, 2, 3, and 4.

Discussion and conclusion
The study of antioxidant properties revealed a very significant activity of all the extracts (chloroformic, n-butanolic, ethyl acetate) with IC50 values comparable to those of ascorbic acid, especially for the chloroformic extract; these results are similar to those of Limem-Ben Amor I. et al; 2009 [8] and Nabti B.; 2023 [9,10]; who attributed this activity to the presence of polyphenols, particularly tannins and flavonoids.It would be interesting to measure these substances and determine whether there is a correlation between their content and activity.

Figure 1 Figure 2
Figure 1 Antioxidant activity curve for ascorbic acid (reference)

Figure 3
Figure 3 Antioxidant activity curve for ethyl acetate extract

Figure 4
Figure 4 Antioxidant activity curve for n-butanolic extract The inhibitory concentrations (IC 50) used to compare the antioxidant activities of the different extracts in relation to ascorbic acid are shown in Figure 5.:

Figure 5
Figure 5 The inhibitory concentrations (IC 50) of the different extracts