Optimization of bioactive compound extraction from tobacco stem (

Tobacco stem represents an underutilized agricultural by-product rich in bioactive secondary metabolites such as phenolics, flavonoids, alkaloids, terpenoids, and saponins. Efficient recovery of these compounds depends on appropriate extraction conditions. The aim of this study was to determine the optimal solvent volume and extraction temperature for maximizing the flavonoid content, phenolic concentration, and antioxidant activity of tobacco stem extract using RSM. A Central Composite Design was applied to evaluate the influence of solvent volume and heating temperature on total flavonoid content, total phenolic content, and antioxidant activity of the ethanol extract. The developed linear regression models demonstrated good predictive accuracy and non-significant lack-of-fit values, indicating model suitability. The optimization analysis predicted the optimal extraction condition at a solvent volume of 80 mL and a heating temperature of 65°C. This prediction was validated experimentally, yielding a total flavonoid content of 2.178 mg QE/mL, total phenolic content of 18.355 mg GAE/mL, and antioxidant activity of 71.159% inhibition. These results confirm that response surface optimization effectively enhances the extraction efficiency of bioactive compounds from tobacco stem, supporting its potential valorization as a natural antioxidant source.