Development and Characterization of Eco-Friendly Bi-Herbal Dye from Curcuma longa and Acacia nilotica with Antimicrobial Properties

The increasing environmental and health concerns associated with synthetic dyes have stimulated interest in sustainable natural alternatives with additional bioactive properties. This study investigated the extraction, characterization, and antimicrobial activities of a bi-herbal natural dye obtained from Curcuma longa and Acacia nilotica. Equal quantities (50 g each) of powdered Curcuma longa and Acacia nilotica pods were extracted using ethanol through Soxhlet extraction technique. The bi-herbal dye product was prepared via recrystallization by mixing equal amounts of the extracted dyestuff (5 g each) in ethanol as solvent. The dye exhibited a percentage yield of 48%, melting point range of 119-122 °C, and a dark brown appearance. UV-Visible spectroscopic analysis showed a maximum absorption wavelength (λmax) at 493 nm, indicating the presence of conjugated chromophoric compounds. FT-IR analysis revealed characteristic peaks at 3619.2 cm⁻¹, 3399.3 cm⁻¹, 1595.3 cm⁻¹, and 1517.0 cm⁻¹ corresponding to phenolic O-H, N-H, and aromatic C=C functional groups. Antimicrobial evaluation using agar well diffusion method showed inhibition zones of 22 mm against Staphylococcus aureus, 19 mm against Escherichia coli, and 28 mm against Candida albicans, compared with standard drugs Sparfloxacin (37 mm and 35 mm) and Fluconazole (32 mm). The Minimum Inhibitory Concentration (MIC) values were 25 mg/ml for Staphylococcus aureus, 50 mg/ml for Escherichia coli, and 12.5 mg/ml for Candida albicans. Similarly, the Minimum Bactericidal/Fungicidal Concentration (MBC/MFC) values were 50 mg/ml for Staphylococcus aureus, 100 mg/ml for Escherichia coli, and 12.5 mg/ml for Candida albicans. The findings demonstrate that the bi-herbal dye possesses broad-spectrum antimicrobial activity with stronger antifungal potency against Candida albicans.