The process of drug discovery and development is intricate and highly demanding, often carrying life-and-death implications for patients. Their well-being depends on the dedication of scientists and clinicians who work to discover, develop, and administer medications aimed at preventing, managing, and treating diseases, injuries, and various health conditions. This journey, from initial discovery to an approved drug, typically spans 12–15 years and involves a financial commitment of roughly one billion dollars. Of the millions of molecules screened, only a small fraction advance to late-stage clinical trials and eventually reach patients as approved treatments 4.

Thiazole was first identified by Hantzsch and Weber in 1887, with its structure later confirmed by Popp in 1889. In the thiazole ring, the numbering begins at the sulfur atom. The basic structure of benzothiazole consists of a benzene ring fused to the 4th and 5th positions of a thiazole ring. Thiazole is a five-membered heterocyclic compound containing one sulfur and one nitrogen atom. Both thiazole and its derivatives, including benzothiazole, serve as fundamental frameworks in the synthesis of numerous thiazole-based compounds. These derivatives exhibit a wide range of pharmacological activities and have proven effective in the treatment of various diseases 5.

Oxygen-containing heterocycles occupy a prominent position among heterocyclic compounds due to their natural abundance and significant roles in biology and medicine 6. Within this group, chromene-based scaffolds stand out for their widespread occurrence in natural products and their diverse and potent biological activities. The term "chromones" originates from the Greek word chroma, meaning "color," highlighting the vivid range of colors displayed by many chromone derivatives. A 4H-chromene (4H-1-benzopyran) is defined as a compound in which a benzene ring is fused with a 4H-pyran ring.

All chemicals used in this study were sourced from Sigma Aldrich (USA). Analytical thin-layer chromatography (TLC) was performed on silica gel G/UV-254 precoated sheets (0.2 mm thick) from Macherey-Nagel (Germany), employing analytical grade solvents. Spots were visualized using either iodine spray (10% w/w I₂ in silica gel) or UV light. Additionally, bioinformatics tools and databases, such as the Protein Data Bank (PDB), alongside software like Autodock and ACD ChemSketch, were utilized. The PDB, established at Brookhaven National Laboratories (BNL), serves as the global repository for structural data of biological macromolecules, including structures determined through X-ray crystallography and NMR methods.

Melting points were measured using capillary tubes and are uncorrected. Infrared (IR) spectra were recorded as KBr pellets for solids on a Perkin Elmer Spectrum FT-IR instrument. ¹H NMR (400 MHz) and ¹³C NMR (100 MHz) spectra were obtained in DMSO-d₆ with TMS as an internal standard, using a Bruker NMR spectrometer. Spin multiplicities are reported as singlet (s), doublet (d), triplet (t), or multiplet (m), with coupling constants (J) provided in hertz. Mass spectra were acquired using a Thermo Finnigan LCQ Advantage MAX 6000 ESI spectrometer.

Table 1

Sr. No.	Compound Code	R
1	R1	6-Cl
2	R2	7-F
3	R3	6-CH3
4	R4	-H
5	R5	6,7-Cl
6	R6	6-F
7	R7	6-OCH3
8	R8	6-Br

To evaluate the anti-tumor activity of a new compound, it is essential to determine its cytotoxic concentration. Cytotoxicity tests identify the highest concentration of the compound that does not harm the cell line. After treatment with the drug, cell death and viability are measured. The results are further confirmed through additional metabolic assays, such as the SRB assay.

The purity of the synthesized compounds was confirmed by measuring the melting point and conducting TLC using a 50:50 ethyl acetate: petroleum ether solvent system. The structures of the compounds were validated through FT-IR, ¹H-NMR, ¹³C-NMR, and mass spectrometry, with the results matching the anticipated structures.

IR spectral data and NMR spectral data:

Figure 14 Figure 15 Figure 16 Figure 17

The synthesized compounds R1, R2, R3, R4, R5, R6, R7, and R8 were assessed for anti-cancer activity using the SRB assay against the A-549 human lung cancer cell line. All the compounds demonstrated moderate to strong growth inhibition of A-549 cells when compared to the control drug, Adriamycin.

Table 3

Code	Human Lung Cancer Cell Line A-549
	% Control Growth
	Drug Concentrations (µg/ml)
	Experiment 1				Experiment 2				Experiment 3				Average Values
	10	20	40	80	10	20	40	80	10	20	40	80	10	20	40	80
R1	86.7	96.7	62.5	18.3	101.9	113.2	84.1	34.7	93.2	92.4	42.5	12.8	93.9	100.8	63	21.9
R2	91.2	89.5	85.6	95.3	101.3	104.9	112.6	93	90.8	92.4	88.9	95.2	94.4	95.6	95.7	94.5
R3	95.2	92.5	90.6	90.3	108.3	106.9	105.6	102.6	97.8	95.4	92.9	90.2	100.4	98.2	96.3	94.3
R4	99.2	96.5	95.6	94.3	110.3	108.9	112.6	102	99.8	98.4	94.9	92.2	103.1	101.2	101	96.1
R5	91.2	87.6	75.6	66.9	102.7	104.9	104.3	56.3	90.1	90.6	61.2	49.9	94.7	94.3	80.4	57.7
R6	96.2	88.5	77	33.5	110.4	111.7	98.6	51	96.2	102	81.7	33.5	100.9	100.7	85.8	39.4
R7	94.9	85.6	80	43.3	104.8	97.6	102.6	75.1	93.6	111.8	82.3	96.2	97.8	98.3	88.3	71.5
R8	96.2	94.5	93.6	90.3	111.3	109.9	106.6	102	97.8	96.4	94.9	92.2	101.7	100.2	98.3	94.8
ADR	10	5.1	-8.4	-1.2	8.4	5	10.4	6.1	4.7	2.6	-3.1	5.4	7.7	4.2	-0.4	3.4

Figure 18

We synthesized 2-(2-(5-nitro-1H-benzo[d]thiazol-2-yl)vinyl)-4H-chromen-4-one derivatives by reacting 2-methyl-1H-benzo[d]thiazole with substituted chromone-3-carbaldehyde in the presence of glacial acetic acid (GAA). The compounds were characterized using IR, 1H NMR, 13C NMR, mass spectrometry, and elemental analysis. Their in-vitro anti-cancer activity was evaluated using the SRB assay against the A-549 human cancer cell line.

The results showed that compounds R1 and R6 reduced cell growth by 21.9% and 39.4%, respectively, at a concentration of 80 µg/mL, while other compounds allowed 57-94% growth. These findings suggest that substitutions on the coumarin nucleus significantly influence biological activity, with unsubstituted (R4), fluoro (R6), and chloro (R1) substituted coumarin derivatives showing significant potency.

The synthesized compounds were characterized by IR, 1H NMR, 13C NMR, and mass spectrometry. Their solubility was tested in different solvents: they were freely soluble in DMSO, soluble in chloroform and methanol, slightly soluble in acetone, ethyl acetate, and ethanol, and insoluble in water. The compounds were assessed for in-vitro anti-cancer activity using the SRB assay against the A-549 human cancer cell line. The results revealed that compounds R1 and R6 inhibited cell growth by 21.9% and 39.4%, respectively, at a concentration of 80 µg/mL, while the other compounds showed 57-94% growth. These findings suggest that substitutions on the coumarin nucleus have a significant impact on biological activity, with unsubstituted (R4), fluoro (R6), and chloro (R1) coumarin derivatives exhibiting considerable potency.

We acknowledged the contributions of the Laboratory staff of B.R Nahata College Pharmacy, Faculty of Pharmacy, Mandsaur University for creating a friendly environment for the synthesis of derivatives and evaluation of Anti-inflammatory activity studies.