Analysis of a "3-(Naphthalen-1-ylimino) Indoline-2-one" compound and Its Antimicrobial Assessment Using Lipid-based Self-nanoemulsifying Formulations

Abstract

In recent years, indole derivatives have acquired conspicuous significance due to their wide spectrum of biological activities-antibacterial, antiviral, and anticonvulsant. This compound is derived from naturally grown plants. Therefore, synthesis of a novel "3-(Naphthalen-1-ylimino) indoline-2-one" compound (2) and its analysis using UPLC systems along with antimicrobial assessment was the aim of the current study. Isatin was used as a parent drug for synthesizing compound (2). Liquid Chromatographic analysis was performed using a C18 BEH column (1.7 µm 2.1 × 50 mm) by UPLC systems. Degradation studies were carried out to see whether acid, base, thermal, and oxidizing agents had any impact on the synthesized molecule in stress conditions (100 °C). A lipid-based self-nanoemulsifying formulation was developed and selectivity, specificity, recovery, accuracy, and precision were measured as part of the UPLC system's validation process. Antimicrobial studies were conducted using gram-positive and gram-negative bacteria. The standard samples were run with a concentration range of 5.0-100.0 µg/mL using the isocratic mobile phase comprising of methanol/water (70/30 %v/v) at 234 nm; good linearity (R² = 0.9998) was found. The lower limits of detection (LOD) and quantitation (LOQ) of the method were found to be 0.81 µg/mL and 2.5 µg/mL, respectively. The coefficients of variation were found to be less than 2%. The antimicrobial study suggests that compound (2) has a substantial growth effect against gram-negative bacteria. It was successfully synthesized and applied to measure the concentrations in lipid-based dosage form, along with potent antimicrobial activities.

Keywords: 3-(Naphthalen-1-ylimino) indoline-2-one; UPLC systems; antimicrobial assessment; method validation; molecule synthesis.

Figure 1

Synthesis of the new molecule “3-(Naphthalen-1-ylimino)indolin-2-one” (2) from the parent compound isatin (1).

Figure 2

¹H-NMR spectra (500 MHz) (A) and mass spectra (B) of 3-(Naphthalen-1-ylimino)indolin-2-one.

Figure 3

The representative UHPLC chromatograms of the blank methanol sample (A), standard solution of compound (2) (model drug), conc. 40 μg/mL (B), standard solution of isatin (parent drug), conc. 5 μg/mL (C) and blank lipid formulation and compound (2) containing lipid formulation sample (D).

Figure 4

The calibration curve of compound (2). The chromatographic conditions used were UPLC Acquity C18, column 1.7 μm (2.1 × 50 mm) maintained at 35 °C temperature, with mobile phase Methanol/water mix. (70/30 %v/v) at flow rate of 0.1 mL/min. A PDA detector was used at 234 nm wavelength.

Figure 5

The UPLC chromatogram showing the systems suitability performance of the sample run. Note: * The chromatographic conditions: A Waters Acquity^®, UPLC C18 BEH column (2.1 × 50 mm, 1.7 μm) kept at 35 °C. The detector wavelength was set at 234 nm for compound (2) and isatin, respectively.

Figure 6

Typical UPLC chromatograms of: (A) acid hydrolysis-degraded compound (2), (B) base hydrolysis-degraded compound (2), (C) oxidative-degraded compound (2) with 3.0% H₂O₂, and (D) thermal-degraded compound (2).

Figure 7

Determination of “3-(Naphthalen-1-ylimino)indolin-2-one” in a lipid-based self-nanoemulsifying formulation (SNEDDS) prepared in-house.

Figure 8

The images show the antimicrobial activities against S. aureus, E. coli, B. subtilis, P. aeruginosa, A. baumannii, Asp. niger, Mycobacterium, and C. albicans. The compounds represent (1) isatin pure drug, (2) compound (2) pure drug, (3) isatin loaded lipid-based formulation, and (4) compound (2) loaded lipid-based formulation. The arrow indicates the maximum zone of inhibition.