Validating Spectrophotometric Assay for Andrographolide and Preparing Its Nanoparticles for Better Inhibition of Breast Cancer Cells

This study validated a sensitive spectrophotometric method for quantifying andrographolide (AG), the major bioactive compound of Andrographis paniculata (Burm. f.) Nees. AG extract was encapsulated into solid lipid nanoparticles (SLNs) to exert anticancer effects on MCF‐7 cells. Ultrasound‐assisted extraction was used for the extraction, and AG was quantified using Kedde's reagent spectrophotometrically. The colorimetric method demonstrated excellent linearity over the concentration range of 10–50 µg/mL with high precision at low (15 µg/mL), medium (30 µg/mL), and high (45 µg/mL) concentrations as indicated by RSD values of 0.63%–1.18%. The method also exhibited good recovery (98.43%–99.67%) and satisfactory sensitivity with limits of detection (LOD) and quantification (LOQ) of 2.14 µg/mL and 6.49 µg/mL, respectively. AG‐SLNs were prepared with injection method to improve the poor solubility and lipophilicity of AG. The particle size, zeta potential, and PDI were 214.3 ± 2.9 nm, −23.57 ± 1.4 mV, and 0.24 ± 0.014, respectively. In vitro release study revealed that AG‐SLNs showed a slower release rate than free AG. The release was fitted with the Korsmeyer–Peppas kinetic model ( R 2 = 0.975, RMSE = 3.53%), indicating a diffusion‐controlled mechanism. The MTT assay indicated that the IC50 of AG‐SLNs was 11.23 µg/mL, lower than that of AG standard and AG extract (14.31 and 18.68 µg/mL, respectively). Therefore, AG‐SLNs enhanced the bioactivity of AG with a better inhibitory action against the growth of breast cancer cells.