Evaluation antioxidant activity and corrosion inhibition of C38 in Hydrochloric acid medium by dried lemon peels of Kenitra Marrakech cities in Morocco and Taiz town in Yemen: A Comparative study

This paper presents a comparative study about the evaluation of antioxidant activity and corrosion inhibition in Kenitra, Marrakesh and Taiz. An interesting topic, indeed polyphenols can improve or help to reduce oxidative stress in the treatment of digestive problems, weight management difficulties, diabetes, hypertension, arteriosclerosis and damage fatty tissue. Therefore, the authors deal with the measurement of polyphenol content and evaluation of the antioxidant activity of lemon peels in Kenitra , Marrakesh and Taiz.The authors performs empirical analyzes on lemon peels. The total polyphenol contents of the ethanolic extract of lemon peels were measured. It was to be 30. 23, 26. 346 and 20.961 mg/CE/g in Kenitra, Marrakech, and Taiz, respectively. Moreover, the DPPH radical scavenging activity of ethanolic extract of dried lemon peels was higher than 200μg/ml concentration. They were 73.47%, 47.36%, and 32.09in Kenitra, Marrakech, and Taiz, respectively. Also, the IC50 values of ethanolic extracts calculated from the percentage inhibitions at the same concentration. Inhibition (IC50) which obtained in Kenitra was 123.089 μg/ml. It was lower compared to the ethanol extract of Marrakech and Taiz that were 197.418, 276.750μg/mL, respectively. Therefore, the extract which is containing a high amount of phenolic is showed high © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/). SHS Web of Conferences 119, 04001 (2021) https://doi.org/10.1051/shsconf/202111904001 QQR’21


Introduction
Antibiotics are widely used to treat or prevent viral and fungal pathogens. Thus, all types of antibiotics depend on its synthetic components and are used as synthetic derivatives [1]. Since penicillin was introducing into medical treatment in 1942, hundreds of antibiotics have been made to saving the lives of humans and animals from infection of pathogens. Also, antibiotics played an essential role in increasing life expectancy witnessed in the second half of the 20th century. Antibiotics also have been used in agriculture and livestock to improve food efficiency in livestock, treat infection and prevent [2]. But the overuse and misuse of antibiotics have resulted in the rapid emergence of chronic disease, which reduced its therapeutic potential against human and animal pathogens [3].
Oxidative stress occurs in an imbalance between free radicals and antioxidants in the human body. Therefore, these sources of free radicals those cause oxidative stress. They have harmful effects such as damaged fat tissue, atherosclerosis, the hardening of the blood vessels inflammatory and high blood pressure [4]. In recent years, the emphasis has shifted to protect cells and lowering oxygen concentrations to avoid oxidative stress. And that by using natural antioxidants that are already found in vegetables, fruits, grains, beverages, and other food products, because it contains crucial compoundsto treatment such as ascorbic acid, Vitamin C, Vitamin E, carotenoids flavonoid, tannins, lignin, and polyphenols [5].
Lemon peels are rich in secondary metabolites such as phenolic and flavonoids. These compounds are responsible for a variety of beneficial biological effects [6].As well as, the compounds organic has shown good corrosion inhibitor activity, which has caused a global concern for of lives humans and the environment. These organic and inorganic inhibitors are non-dissolving, if we would add a hydrochloric acid solution to them [13,14]. So they are harmful to humans and the environment during the synthesis and application [15,16].The current study focused on plants, because they contain secondary metabolites and natural organic compounds and include sulfur, nitrogen and oxygen [17,18]. In addition, they are non-toxic, inexpensive, and we can get benefit from the remnants of its peels [19].

Soxhlet and Hydro distillation apparatus
Using hydrodistillation to extract the essential oils of dried lemon peels according to the European Pharmacopoeia protocol [20]. Using a Soxhlet apparatus to extract Ethanol from dried lemon according to Lin protocol [21].

The Folin-Ciocalteu
Using of Folin-Ciocalteu to evaluate the polyphenol content of ethanol extract for dried lemon peels of Marrakech, Kenitra and Taiz according to Lister and Wilson [22].

Electrode and Solution
Using an electrode and solution for corrosion test on electrodes of C38 plates of ethanol extract of dried lemon peels of kenitra and Taiz cities.

Electrochemical measurements
Using of potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS), which are performed in a three-electrode cell.

Results and Discussion
The results of the current study were in the yield, total Polyphenol Content, and evaluation of Antioxidant Activity of dried peels lemon of Marrakech, Kenitra and Taize.In addition, corrosion inhibition of C38 in 1 M Hydrochloric acid by ethanolic extract of dried lemon peels of Kenitraand Taiz.

The yield of dried lemon peel extracts
The yield rate of the essential oils in Marrakech , essential oils in Kenitra , ethanol extract in Marrakech , ethanol extract in Kenitra , and ethanol extract in Taiz Ewere 0.31%, 0.42%, 18.39%,25.553%, and 13.43 % respectively In Table 1.

Total Polyphenol Content
The standard curve (y = 0.001 x-0,001, r2 = 0.995) to determine the total polyphenols content which obtained by measuring the absorbance of the standard solution for Gallic acid and is shown in Table 2 and Fig 1. The concentrations of total polyphenols obtained were presented in (Table 3). They were expressed in µg EAG / g ES.

Antioxidant Activity (AA)
The table (4) and Fig (2) clarify the radical scavenging activities by using of (DPPH) which evaluated of standard ascorbic acid at different concentrations. In Table ( 5) and Fig  (3), the radical scavenging activities were evaluated at different concentrations of extract ethanolic of dried lemon peels of Marrakech, Kenitra andTaiz. In Table 6, there are a comparison between the total phenolic content and IC50 values of ethanolic extract for the dried lemon peels of Marrakech, Kenitra andTaiz.

Adsorption isotherm
The adsorption parameters and Langmuir isotherm curve of C38 in 1M hydrochloric acid for the ethanolic extract of lemon peels in Kenitra and Taiz obtained from the adsorption isotherms according to Langmuir in Table 7 and

Polarization curves
Their extrapolation parameters and inhibitory efficacy values presented of extracts as in Table 8, 9. Obtained Tafel curvelines in various concentrations are shown of extracts as in Fig 5, 6.

Electrochemical impedance spectroscopy (EIS)
Impedance curves which obtained in various concentrations with the absence and presence of extracts are shown as in Fig 5, 6.
The Electrochemical parameters which obtained in various concentrations with the absence and presence of extractsare shown as in Table 10, 11. To get a usable digital data, the electrical equivalent circuits are shown as in Fig.9.

Discussions
It is clear from the obtained results in Table 1.The yield rate of essential oil in Kenitra was 0.42% higher than the yield in the Marrakech, which was 0.31%. Moreover, the yield rate of extracted ethanolic in Kenitra was (25.553%) higher than the yield in the Marrakech . It was sequentially 18.39% higher than the yield in the Taiz which was (13.43 %). The obtained results in this work showed less rate of the yield comparing with another study in the North East of Tunisia by 1.30%, but they were a similar to the results which are introduced by Lota et al, where the yield was about 0.05% to 0.60% [24]. Therefore, the changes in these results were depended on the natural environment, extraction procedure, climate, distance, proximity to the sea, elevation, ecological conditions, mode of operation (drying -distillation method), harvest and ripening time [25], ecological conditions [26] and water shortage conditions [27]. It is clear from the obtained results in Table 3. The ethanolic extracts of the lemon peels are subjected to screening for their total polyphenols contents. The polyphenols content of ethanolic extract in Kenitra was 30. 23µg/ml. It was relatively high comparing with the ethanolic extract in Marrakech and Taiz, which were 26.34 and 20.96 µg/ml respectively. Therefore, they can free radical scavenging using DPPH free radicals.
In Table ( 5,6) and Fig (3,4), the free radical removal activity evaluated by using of DPPH for ethanolic extract of dried lemon peels.  Table 7 indicates that the adsorption of inhibitors follows the Langmuir model as the correlation coefficient (R2) for both inhibitors was 0.99 %. Therefore, the experimental data gave an excellent curve fitting for this adsorption isotherm, and the negative value of the standard free energy of adsorption ΔG°adsindicated the spontaneous adsorption process (physisorption). Through Fig 6, 7 for the Tafel curve, we notice a decrease in the cathode and anode current. Therefore, this inhibition is from mixed-type.
In Table 8, we observe the polarization parameters when increasing inhibitor concentration at 2 mL L-1 and lower corrosion current density (Icorr) by 114.64 µA/cm2. The inhibition efficiency increased (IE %) by 98.12 % in Kenitra. For Taiz in Table 9, the inhibition efficiency was 84.85%. It was less compared with inhibiting efficiency in Kenitra.
In Table 11, it is clear that Impedance parameters when there was increasing inhibitor concentration at (2 mL L-1), there is increasing Charge transfer resistance (Rct) to the value 862.2 Ω.cm2, whereas there is a lower double-layer capacitance (Cdl) by 1.02. Also, there is increasing in The inhibition efficiency IE % to 82, 14 % in Kenitra. For the obtained results in Taiz as in Table 10, the inhibition efficiency was 80, 00%, which was less than inhibiting efficiency in Kenitra. This indicates to a decrease in the active surface area which caused by the adsorption of the inhibitors on the carbon steel surface and that the corrosion process became hindered as a result to a decrease in the local dielectric constant and increase the thickness of the electric double layer [28], which decreased the extent of dissolution reaction [29,30].

Conclusion
This study confirms the highest percentage of the yield, total polyphenol content, antioxidant activity, and the inhibition efficiency of the extracted ethanol of lemon peels in kenitra city and the lowest percentage of Marrakech and Taize cities. It is due to many factors that including the difference in climate, proximity to the sea and altitude, environment conditions. The lemon fruit considered the most global produced with about six million metric tons. Its production in Morocco amounted to about 44,000 thousand metric tons. Therefore, one of the proposed recommendations in the future is to exploit lemon peels to extract their chemical compounds as a medicinal product and rid the environment of those peels in a friendly and purposeful manner.