SYNTHESIS, EVALUATION, AND STRUCTURAL CHARACTERIZATION OF ANTIOXIDANT DIORGANOTIN(IV) COMPLEXES DERIVED FROM AMPICILLIN: A COMPREHENSIVE STUDY

. This study offerings the preparation, structural analysis, and estimation of novel diorganotin(IV) complexes derived from an ampicillin as a ligand in terms of their antioxidant activity. The diorganotin complexes were yielded by a direct reaction between ampicillin and a different number of diorganotin(IV) chloride precursors. Various spectroscopic techniques, including CHNS, FTIR and nuclear magnetic resonance ( 1 H, 13 C, 119 Sn NMR), were used to explain the molecular structures of the produced complexes. Through in vitro experiments such as the CUPRAC and DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging technique, the novel diorganotin complexes' antioxidant activity were assessed. The results were compared to that of ligand antioxidants to evaluate the effectiveness of the complexes that were produced. The structural properties of the complexes were linked to their antioxidant capacity to identify the connection between molecular structure and biological function.


INTRODUCTION
Antioxidants are important for inhibiting damage from free radicals and oxidative stress in biological systems [1].Organotin complexes have been investigated in the quest for new antioxidant molecules and have demonstrated encouraging antioxidant qualities [2].The ampicillin ligand, which has distinct structural characteristics that make it a useful ligand to produce organotin complexes, is the source of the novel organotin(IV) complexes that are the subject of this study's evaluation of antioxidant activity [3,4].
Because of their complementary properties, ampicillin and organotin(IV) moieties together may create molecules with improved antioxidant capacity.Various investigations have highlighted the numerous biological functions of organotin(IV) complexes, such as their antitumor, antibacterial, and anti-inflammatory characteristics [5].But little is known about their structural makeup and antioxidant capacity, particularly when it comes to ampicillin-based ligands.The coordination geometry, molecular structure and bonding interactions with the complexes will be better understood thanks to these approaches [6].The assessment of antioxidant activity will be carried out using validated assays, including total antioxidant capacity (TAC), ferric reducing antioxidant power (FRAP) tests and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging [7].One stimulating option for the creation of new compounds with improved biological activity in the field of organotin(IV) complexes is the addition of ligands from popular antibiotics, such ampicillin.One beta-lactam antibiotic that is well-known for its antibacterial qualities is ampicillin [8].But the investigation of its potential as an organotin(IV) complex ligand offers up new therapeutic uses beyond its traditional use [9].Numerous scholarly investigations have emphasized the importance of organotin(IV) complexes in demonstrating antioxidant characteristics [10,11].These complexes have the capacity to reduce oxidative stress and scavenge free radicals, which may be advantageous in the setting of a number of disorders [12].Determining the medicinal potential of organotin(IV) complexes generated from ampicillin ligands requires an understanding of their antioxidant activities [13].The results of these tests will be used to assess the overall antioxidant capacity and free radical-neutralizing potential of the organotin complexes.By shedding light on the antioxidant potential of organotin(IV) complexes formed from the ampicillin ligand, this study seeks to advance knowledge of these compounds' possible uses in the pharmaceutical and medical industries.A thorough understanding of the characteristics and possible medical advantages of these novel compounds will be possible through the combination of structural characterization and antioxidant assessment [14,15].In this work, novel complexes of diphenyl, dibutyl, and dimethyl-tin were created by using ampicillin as a ligand in a condensation process with the respective organotin chloride ions.The diorganotin(IV) complexes demonstrated a greater percentage inhibition in both DPPH and cuprac techniques compared to the ligand, suggesting the important significance of the tin moiety in boosting the complexes' antioxidant activity.In addition, out of all the complexes, the diphenyl tin carboxylate complex exhibited the highest level of antioxidant activity.These findings imply that the produced complexes may be used to create novel antioxidant-active medicinal medicines.[16] High yields were obtained when diorganotin(IV)-ampicillin complexes were synthesized at a molar ratio of 1:2.To make the complexes, excess ampicillin was reacted in methanol with trisubstituted tin chloride (diphenyl, dibutyl, and dimethyl tin dichloride) for five hours under reflux.The resultant solution was filtered, dried, and recrystallized to create a precipitate.Table 1 illustrates the weights and molar ratios of the diorganotin(IV)-ampicillin complex.Scheme 1 shows the synthesis of diorganotin complexes.Table 1.The weights and molar ratios of diorganotin(IV) complexes and ligands.

Assay for scavenging free radicals with DPPH
Antioxidants were determined according to their capacity to neutralize free radicals.The activity of radical scavenging was evaluated using the radical 2,2-diphenyl-1-picrylhydrazyl by microplate reader spectrophotometry at λmax= 490 nm, as per the usual procedure.The reaction mixture contained DPPH (200 µg/mL) and test complexes in methanol (50 µg/mL).The reaction was tested for five, ten, and fifteen minutes.The data was calculated using Microsoft Excel 2010 [17,18].The % inhibition was calculated using the procedure below (Equation 1).
where A blank is the absorbance of the control reaction (all reagents except the test complex), and A sample is the absorbance of the test complex [19].

Identification of diorganotin(IV)-ampicillin complexes
The elemental composition of the diorganotin(IV)-ampicillin complexes were determined using CHNS analysis.The results agree with the calculated values of the ligand (ampicillin) and its complexes in general (Ph2SnL2, Bu2SnL2 and Me2SnL2).Table 1 shows the elemental analysis data of (C, H, N, S and Sn %) colors, melting points and yields of diorganotin(IV)-ampicillin complexes along the ligand.Table 2 illustrates the physical data of the diorganotin(IV)-ampicillin complex.

FTIR spectrum
The carboxylic group Figure 1 in ampicillin causes it to show a significant absorption peak in the ligand spectrum at 1775 cm -1 when the principal FTIR frequencies of ampicillin and its diorganotin(IV) complexes are compared.Additionally, a stretching band in the 3600-2400 cm -1 region is associated with the stretching vibration of carboxylic acid's hydroxyl group -OH [22].
On the other hand, after complexation between the ligand and organotin was evident from the significant shift in wavelength of these groups' vibrations in comparison to the ligand's [23].These bands are attributed to Sn-O and Sn-C resonances, which are found in the 572-530 and 464-422 cm -1 areas, respectively.Such bands confirm that the ligand and metal ion are coordinated [24,25].

Nuclear magnetic resonance spectroscopy
Diorganotin(IV) moiety in complexes has a smaller up-field shift.As the tin atom's coordination number rises, the chemical shift also rises [26].All complexes revealed the ligand's N-H proton as a singlet, indicating that the N atom does not coordinate with the tin center.In terms of synthesizing compounds, the 1 H-NMR data matched the 13  complexes.Because oxygen is connected to an electropositive tin atom, the complexes' C3carboxyl was pushed downfield relative to the ligand site.It is demonstrated by this data that complexation took place through the oxygen atoms in the carboxylic group.When analyzing the 119 Sn-NMR spectra of Ph2SnL2, Bu2SnL2, and Me2SnL2 complexes, which resonant at -298.52, -262.50, and -211.20 ppm, respectively, it falls within the range of hexa-coordinated diorganotin(IV)-ampicillin [27,28].Table 4. 13 C-NMR spectra (DMSO-d6; ppm) of ampicillin and its complexes.

Scavenging technique of DPPH radicals
The antioxidant capability of diorganotin(IV)-ampicillin complexes was assessed by dissolving them in methanol at a fifty-μg/mL concentration for every test solution.Following 5, 10, and 15 min, the absorbance of the solutions was measured using a microplate reader set to an optimal wavelength of 490 nm.Based on the data acquired, Equation 1 was used to calculate the percentage of inhibition against DPPH.Plotting the relationship between the percentage of inhibition and time allowed for the identification of the complexes with the highest inhibition.
There will be a decrease in the DPPH radical (light yellow solution).Diorganotin compounds are expected to be antioxidants because of the presence of the metal moiety [29,30].
Table 5.Data for evaluating the antioxidant activity of ampicillin and its complexes at different times.
The complex Ph2SnL2-A exhibited higher percentages of scavenging than the ligand ampicillin.This is due to the presence of the two phenyl groups in addition to the increase in aromatization.The complexes' percentage of dose-dependent inhibition was determined by employing a concentration range of 25-75 μg/mL.That the complex's ideal concentration for high inhibition was 50 μg/mL.Tannic acid was selected as the typical antioxidant component; nevertheless, its scavenging percentage was higher than that of the organotin(IV)-ampicillin complexes [31][32][33]

Assay for CUPRAC activity
The cuprac test evaluates antioxidant activity by measuring the decrease of Cu 2+ in an excess of neocuproine using a reducing agent.This leads to the production of a Cu + blend with an optimal wavelength of 450 nm [34,35].At a concentration of 20 μg/mL, the absorbance and percentage inhibition were determined for every complex, ligand, ampicillin, standard reference, and tannic acid.The reference antioxidant, had consistently higher antioxidant activity when compared to these substances.Tannic acid is the effective natural antioxidant component that can be used as food preservative agents or nutraceuticals.[36,37].However, as Table 6 and Figure 4 demonstrate, Ph2SnL2-A complexes have more antioxidant activity than their ligand.Table 6.Displays the absorbance and percentage inhibition of Ampicillin, Complexes, and Tannic Acid at a concentration of 20 µg/mL.The study evaluated the antioxidant activity of the diphenyltin(IV)-ampicillin complex at varying doses (20, 40, and 60 μg/mL).To maximize antioxidant activity, the best dose was found to be 40 μg/mL based on absorbance and inhibition ratio.

CONCLUSION
Diorganotin(IV) complexes were created via condensation reactions with ampicillin.Antioxidants were utilized throughout both the DPPH and CUPRAC procedures.All synthesized complexes have higher antioxidant activity than ligand-derived complexes.The findings show that the Ph2SnL2-A complex performed better in both operations.

Table 3 .
The 1 H-NMR spectra of ampicillin and its complexes. .