DFT can provide insights into the interactions between the plant extract and the metal surface, as well as the mechanism of inhibition, the importance of the theoretical (DFT) study can be presented in the following points:

· Molecular structure and stability: DFT allows for the determination of the optimized molecular structure of the plant extract and its stability.

· The geometry optimization can reveal important information about the active chemical constituents responsible for corrosion inhibition.

· Adsorption on a metal surface: DFT can investigate the adsorption behavior of the plant extract on the metal surface. The interaction between the extract's chemical constituents and the metal surface can be analyzed to determine the adsorption energy and the mode of interaction (e.g., chemisorption or physisorption). Stronger adsorption generally indicates better corrosion inhibition efficiency.

· Charge transfer and electronic properties: DFT can provide insights into the charge transfer processes occurring at the metal-extract interface. By examining the electronic properties, such as the frontier molecular orbitals and electron density distribution, one can assess the potential for electron transfer between the extract and the metal surface. This information contributes to understanding the inhibition mechanism.

· Thermodynamic parameters: DFT calculations can estimate thermodynamic parameters, such as the free energy of adsorption, which can shed light on the spontaneity and feasibility of the inhibition process. Additionally, calculations of reaction barriers can provide information about the kinetics of the inhibition process.

· Comparative analysis: DFT allows for a comparative analysis of different plant extracts or their constituents to identify the most effective inhibitors. By calculating the relevant parameters for multiple extracts, researchers can determine which ones exhibit better corrosion inhibition properties.

· It's important to note that DFT results are typically complemented by experimental studies to validate the theoretical findings. Nonetheless, DFT can provide valuable insights into the molecular-level interactions between the plant extract and the metal surface, aiding in the design and optimization of corrosion inhibitors.

· Please keep in mind that the specifics of the DFT results will depend on the particular plant extract, the metal substrate, and the methodology employed in the study.