Visibility, Selectivity, Optimization, and Interaction of Natural Tannin Dye from Ceriops tagal (Perr.) C.B. Rob. Extract for Plant Tissue Staining

Tissue staining improves cellular visualization for microscopic analysis. This study explores tannin dye from Ceriops tagal as a sustainable, eco-friendly alternative for plant histology. Its strong affinity to cotton cellulose suggests effective staining potential. The research assesses tissue visibility, mordant specificity, color contrast, and dye–tissue binding interactions. Tissue staining enhances the visualization of cellular structures, facilitating microscopic analysis. Developing safe, cost-effective, and environmentally friendly natural dyes is essential for sustainable histological applications. Tannin dye extracted from C. tagal binds effectively to cotton cellulose, indicating its potential for plant tissue staining. This study evaluates the visibility of stained plant tissues, mordant selectivity, color contrast optimisation, and chemical bonding interactions. The stem sections of sunflower (Helianthus annuus L.) were stained with C. tagal tannin dye. Mordants used included ferrous sulfate (FeSO₄), aluminum sulfate (Al₂(SO₄)₃), and calcium carbonate (CaCO₃), with synthetic safranin serving as a control. Color contrast optimization was performed using response surface methodology (RSM), analyzing dye concentration, immersion duration, and mordant concentration. Color contrast (ΔE) was measured using colorimetry via a smartphone application, while chemical interactions were examined through Fourier transform infrared (FTIR) spectroscopy. The results showed that tannin dye adhered well to plant tissues, producing colors ranging from sepia brown to baker’s chocolate. Al₂(SO₄)₃ produced the highest contrast (ΔE = 79.7). Optimal staining conditions were achieved with 44.233 g/L tannin dye, 73.636 s of immersion, and 110.454 g/L Al₂(SO₄)₃ as the mordant. FTIR analysis revealed bonding interactions, evidenced by peak intensity shifts at 2922 and 1100 cm⁻¹. C. tagal tannin dye demonstrates strong potential as a natural, sustainable plant tissue stain with effective mordant selectivity and contrast. Further research is recommended to expand its application across diverse plant species and to standardize protocols for broader histological use.