Datura metel fruits were harvested in Téorou Mbaye, a village located in the Gossas department in Senegal, with the following geographical coordinates: latitude 14.48 North, longitude 16.01 West and altitude 25.00 m/82.02ft. After identification by the botanical laboratory of the Faculty of Medicine, Pharmacy and Odontology at Cheikh Anta Diop University in Dakar, the fruits were dried in the dark at room temperature for 15 days. The seeds obtained from the dried fruit are then ground using an electric grinder. The crushed seeds are stored in a refrigerator at 4˚C until use.

a. Extraction of Datura metel seed oil.

A 100 g mass of Datura metel seed powder was extracted by Soxhlet with hexane for 1 hour. The resulting mixture was then evaporated to dryness using a rotary evaporator. The resulting oil was weighed and the extraction yield calculated as a percentage (weight/weight) based on the weight of the dried seed powder.

b. Analysis of oil physicochemical parameters.

The analysis of the physicochemical parameters of the oil was carried out by determining the acidity index, peroxide, iodine, density and pH respectively described by the methods of Boulfane et al. [17] , Novdizro et al. [18] and Nasma et al. [19] .

Plant-parasitic nematodes are uniform in appearance, invisible to the naked eye and possess hollow needles connected to a hypertrophied glandular system [20] . Meloidogyne javanica nematodes were extracted using the method described by Baermann [21] . It consists of extracting nematodes from infested tomato roots (Mongal variety). First, the gall roots were washed with water and then cut into small pieces about 1 cm long. Part of the resulting mixture was then sieved using 100 µm diameter sieves. The sieve was then soaked in water and incubated for a week in a petri dish. The resulting nematode solution was observed under a microscope to confirm the presence of Meloidogyne javanica and stored at 4˚C until use.

Gas chromatography (GC) (GCMS-QP2010-SE) equipped with a DB-5MS UI column (30 m × 0.25 mm inner diameter; film thickness: 0.25 μm), used as stationary phase, and directly connected to an A0C-20I mass detector, was used to analyze the oil after the methylation phase. High-purity helium (99%) was used as carrier gas with a flow rate of 0.97 mL min⁻¹ and a pressure of 70.7 kPa. A sample volume of 1 μL was injected via an autosampler in a 1:20 split ratio. The mass spectrum was acquired in full scan mode with electron ionization (EI) at 70 eV. The mass spectra bank of the Faculty of Pharmacy of the Université Paris Cité was used for compound identification by closest match of the mass fragmentation pattern.

The antiradical activity of Datura metel oil was measured using the method described by Molyneux et al. (2004), described in our previous studies [22] . It involves reducing the stable, violet-colored free radical of the DPPH molecule to a yellow color visible at 517 nm.

Concretely, to a volume of 50 μL of a solution of the oil at different concentrations (6.25 - 12.5 - 25 - 50mg/mL), is added 200 μL of a DPPH solution (0.04 mg/mL). The resulting mixture is then incubated for 30 min before absorbance readings are taken at 517 nm using a spectrophotometer. Inhibition percentage (IP) is then calculated from the absorbances using the formula below (Equation (1)).

$PI=\frac{A0-Ai}{A0}\times 100$ (1)

A0 = absorbance of DPPH; Ai = absorbance after addition of extract.

Ascorbic acid, used as a reference, was tested under the same conditions as the oil. Three measurements were taken for each concentration of product tested.

The in vitro nematicidal activity of the oil was evaluated according to the method described by Yuji Oka et al. (2000) with a slight modification [23] .

Three concentrations of 25, 50 and 100 µg/mL were prepared from Datura metel oil using a mixture of tween 40/water (0.3/9.7 w/w) as the dilution solution.

A mixture of 1 mL nematode solution and 500 µL diluted oil solution is placed in a tube. The resulting mixture is incubated at room temperature for 24 and 48 hours. The number of dead nematodes (inert for 10 s) is then quantified using an optical microscope. A negative control consisting of water was produced under the same conditions. The water mortality rate, corresponding to natural mortality, was subtracted from the oil mortality rate. All experiments were conducted in triplicate.

Sand was extracted from a depth of 50 cm, sterilized to prepare 50 pots for Mongal tomato plants. Each pot was filled with 5 kg of sand, then sprinkled with 500 mL of water. After 24 hours, 2 tomato plants per pot are transplanted and watered with the same volume of water. After 5 days of growth, the sand is enriched by adding 0.6 g of urea and 0.7 g of NKP fertilizer (10-10-20) for each pot of tomatoes. This last operation is repeated every 10 days for 1 month.

After one month’s growth, tomato roots are infected with 15 mL of the previously prepared nematode solution and immediately treated with 500 µL of the oil solution at concentrations of 50 and 100 µg/mL. The treated pots are then incubated for 15 days before the roots are analyzed under a magnifying glass to determine the nematode mortality rate using the following formula described by Ghareeb et al. (Equation (2)) [24] .

$\text{\% of mortality}=\frac{\text{Treatement mortality}-\text{Control mortality}}{\text{Control mortality}}\times 100$ (2)

Collected data were entered into Excel to design tables and graphs for analysis. Statistical analysis was performed using ANOVA variance (p < 0.05).

The physicochemical parameters of Datura metel oil are given in Table 1 .

Extraction of Datura metel seed powder using a Soxhlet in hexane allowed to obtain an oil with 15% yield. The oil yield extract may depend on a number of factors, including soil and climatic conditions, the nature of the solvent and the extraction time [25] . However, oil extraction using hexane and Soxhlet gave yields of 29; 22 and 20% from seeds of white mustard, caraway and coriander respectively [26] . The physicochemical parameters described in Table 1 show that Datura metel seed oil is a good quality, stable and slightly acidic oil (pH = 5). In fact, this oil has acidity and peroxide values of 0.3% and 10 meq.O2/Kg respectively, slightly similar to those of olive oil, often used as a reference oil [27] . This means that the oil has not undergone significant oxidation and that it is suitable and has a shelf life. The peroxide value confirms that the oil is extra virgin.

The iodine value of Datura metel oil is 57.105 mg I2/100g, placing it among the non-drying oils for which the iodine value is between 0 and 110 mg I2/100g oil [18] .

Determination of the chemical composition of Datura metel seed oil by gas chromatography-mass spectrometry (GC-MS) revealed the presence of 30 molecules in the oil. These molecules are listed in Table 2 below, along with their retention times and weight percentages. Among these compounds, the most significant was detected after 17.93, 21.335, 21.487 and 21.734 minutes of retention, corresponding to at least 74% of the oil weight. These compounds, known respectively as Eicosanoïc acid, methyl ester; Methyl-10-trans-12-cis-Octadecadienoate; 9-octadecenoic, methyl ester (E) and Methyl stearate, are fatty acid esters. The measured iodine unsaturated fatty acids are Methyl-10-trans-12-cis-octadecadienoate; 9-octadecenoic, methyl ester (E) and 9,12-octadecandienoic acid (Z,Z)-2-hydroxy-1-(hydroxymethyl) ethyl ester with 22.4; 23.04 and 3.24%, respectively, of total oil weight. Datura metel oil also contains small quantities of steroids: Stigmata-5,24-(28)-dien-3-ol, (3-beta-24E); Ergost-5-en-3-ol, (3-beta.); Stigmasterol; Stigmasta-5,24 (28)-dien-3-ol, (3.beta-24Z) but also other polycyclic fatty acid esters such as: Olean-12-en-3-ol, acetate, (3-beta.) and Olean-12-en-3-ol, acetate, (3-beta.). These results show the heterogeneity of molecules present in Datura metel seed oil.

R. Time: retention time; ND: Not determined.

The results of free radical scavenging activity by DPPH radical reduction are given in Table 3 below. Inhibitory concentrations (IC₅₀) are calculated from linear regression equations resulting from inhibition percentages as a function of oil concentration. The IC₅₀ of the oil indicates a low antiradical activity (222.31 mg/mL) compared with that of ascorbic acid, used as a reference (0.022 mg/mL).

Although this activity is low compared to ascorbic acid, it proves more interesting than some essential oils tested on the DPPH radical. Indeed, studies by Rachid et al. (2017), Samah et al. (2015) gave antioxidant activities of essential oils ranging from 1000 to 2260 mg/mL [28] [29] . Natural antioxidants are currently the subject of numerous studies in the preservation of food and phytosanitary products. They are thought to play an important role in the treatment of diseases in which oxidative stress is involved [28] .

In vitro results for nematicidal activity are expressed as mortality rates as a function of oil concentration ( Figure 1 ). After 24 hours, the oil showed mortality rates of 11%, 46% and 47% at concentrations of 25, 50 and 100 µg/mL respectively. These mortality rates are more significant after 48 hours of incubation.

An in vitro study of the nematicidal activity of Datura metel oil showed significant toxicity to Meloidogyne javanica nematodes at the J2 stage. The oil caused 11, 46 and 47% mortality within 24 hours, and 58, 69 and 79% mortality within 48 hours of incubation with oil concentrations of 25, 50 and 100 µg/mL respectively. This highly significant mortality is dose-dependent and could be linked to the high content of eicosanoic acid, methyl ester; methyl (10E,12Z)-Octadecadienoate; methyl ester 9-octadecenoic acid and methyl (E)-stearate, which together account for over 74% of the total oil’s weight. These fatty acid esters have also shown significant nematicidal activity against Meloidogyne incognita on bananas [30] . Other saturated fatty acid esters such as methyl pelargonate and ethylene glycol pelargonate caused mortality rates on Meloidogyne incognita of up to over 90% [31] . Further work by Ramadan et al. on four commercial oils obtained from Cytrullus colocynthis, Simmondsia chinensis, Moringa oleifera seeds and marjoram oil showed interesting activities in inhibiting egg hatching and high mortality of Meloidogyne incognita. The longer the incubation period, the greater the effect [32] .

Statistical analysis showed that concentration of oil had a significant effect on nematode mortality. Indeed, the degrees of freedom are 8 and 3; the f-values are 6.1729 and 37.0374 and the p-values < 0.05 for oil and concentration respectively.

On the other hand, the interaction between concentration and oil had no significant effect on mortality (degree of freedom 24, F value 1.1225 and p value > 0.05).

The in vivo results of the nematicidal activity of Datura metel oil on Meloidogyne javanica nematodes at the J2 stage, expressed as infection rate as a function of concentration, are shown in Figure 2 .

These results show that Datura metel oil also has protective activity against infection of the tomato roots studied. Indeed, after 15 days of treatment, nematode mortality remained at 54% for concentrations of 50 and 100 ug/mL, showing that this activity is not dose-dependent.

Statistical analysis by ANOVA indicates that oil has a significant effect on infection rate. Indeed, the degrees of freedom were 6 and 1, the f-values were 778.7 and 97.8, and the p-values were <0.05 for oil and concentration respectively. However, the interaction between concentration and oil had no significant effect on the infection rate (p > 0.05).

Due to their complex composition, oils extracted from plants can affect several targets simultaneously, reducing the likelihood of target organisms developing resistance or adapting to the treatment. The mode of action of essential oils against nematodes is not very well defined, but in insects, several essential oils inhibit acetylcholinesterase activity and consequently affect the insect nervous system [23] . Other authors stipulate that essential oils act on nematodes via a variety of mechanisms, including disrupting their nervous system, inducing adverse effects on plasma membrane permeability, penetrating the gelatinous matrix of nematode eggs and disrupting intracellular redox status [33] .