*3.3.3 Analysis of SPLET mechanism*

In water, the parameters BDE, IP, and ETE having higher enthalpy than PA and are represented in **Table 4**. Hence SPLET is the mechanism followed by each molecule in the water medium. In the SPLET mechanism, the heterolytic bond cleavage of the phenolic hydroxyl group is considered, and the neutral molecule is split into an anion and a proton. The numerical parameter associated with this step is PA. The anion produced donates one electron to free radical species, and the free radical receives one electron and forms an anion. The anion of free radical react with proton forms a neutral compound by leaving the anion starting compound as radical. The numerical parameter associated with this step is ETE. The values of PA are found to be lower than BDE and other parameters in all studied cases when the solvent was aqueous. In the case of **1a**, 4' OH possesses the lowest value of PA (35.27 kcal/mol), contributing to the radical scavenging mechanism.

In the case of **1b**, the PA value of 7 OH (36.41 kcal/mol) has a lower value, and 5 OH (37.08 kcal/mol) and 4' OH (37.11 kcal/mol) have valued at the nearest. When glucose at position 3 enhances the electron-donating capacity of A ring. When glucose at 4<sup>0</sup> position called **1d**, the lowest PA value at 3-OH (35.21 kcal/mol) and followed nearest at 7 OH (35.80 kcal/mol) and 5-OH (36.36 kcal/mol) also enhances the radical scavenging activity of A- ring. The lowest PA value of **1c** in water is 4' OH (34.39 kcal/mol), which is the lowest of all studied compounds in the water medium. The PA values 35.10 kcal/mol of 7 OH and 5 OH are near the 4' OH. For **1e**, the lowest value of PA at 5-OH (36.07 kcal/mol). In the water medium, the gallate moiety containing hydroxyl group does not affect radical scavenging activity due to its higher PA values. In the gas phase, a considerable contribution is provided by this group.
