The are also calculated by using same level theory.

old-fashioned medicine used for the management of liver disorders are very
useful for documentation of the natural product which responsible for the
hepatoprotection 1-3. The monoterpene glucoside, loganin is byproduct in
biosynthesis of corynanthe, Aspidosperma, Iboga, Cinchona, Ipecacuanha and
pyrolochinolin alkaloids 4 known as monoterpene glucoside 5. Loganin is one of the best-known of the iridoid glycosides. It is named for the Loganiaceae, having first been isolated from the seeds from member Strychnos nux-vomica family. 6Here,
in the present communication, we calculate chemical as well as biological
activity of Loganin by using combination of DFT/B3LYP method and 6-311G(d, p)
basis set. Nonlinear optical properties are also calculated by using same level
theory. The purpose of this study assumes some modification in
oxidation/reduction on polyfunctional bioactive natural product will generate
new reactive sites in the molecule.The logain shows Sofa type structure. The loganin contains three
rings in which two are hexa and one is penta ring. In both hexa ring one carbon
is replaced by oxygen. This oxygen contain two lone pair electron create
antibonding repulsion so these ring slightly displaced from planarity. QTAIM
calculations are done for the finding and description of hydrogen bonding
within title molecule. In the outline of QTAIM, the hydrogen bonding is
explored by presence of BCP between proton donor and acceptor atoms. QTAIM
delivers a number of topological restrictions at BCP viz. charge density (?BCP)
and corresponding Laplacian (?BCP), kinetic
energy density (G), potential energy density (V) and total energy density (H).
Hydrogen bonds are characterized as weak and electrostatic in nature for ?BCP> 0 H
> 0 and for strong as well as covalent nature ?BCP< 0 H < 0 at BCP 16. According to our calculations, there exist five intra-molecular H-bonds in title molecule. Topological parameters associated with these H-bonds are listed in Table 2. Apparently, all H-bonds are found to be medium and weak. The interaction energy of H-bond can be calculated as Eint = ½ (VBCP) 17. In our calculation O23-H35, O36—H38, O23-H22,O19-H18 are hydrogen bond with medium strength however  O31-H28 hydrogen bond  is weak strength.In logain calculated dipole moment value is 1.79.Debye. Logain having lower dipole moment as compared water (2.16 Debye), loganin can be used as better solvent. In polarizibility calculation greater contribution of ?xx, ?yy, ?zz which shows that molecule is elongated more towards, X,Y Z direction. Total hyper-polarizibility of title molecule is 51 times greater than Urea. So this shows that title molecule shows a good candidate for NLO. The interface with other types in a chemical system is also resolute by frontier orbitals, HOMO and LUMO. The frontier orbital gap helps to differentiate the chemical reactivity and kinetic stability of the molecule. The molecule which has a larger orbital gap is more polarized so more reactive far as reaction is concerted 25. The frontier orbital gap in case of the loganin is 13.60eV. The contour plots of the HOMO, LUMO structure of the loganin are shown in Figure-3.  HOMO and LUMO both located at ring R3. HOMO act primarily donor and LUMO act primarily acceptor. So HOMO-LUMO   The importance of MESP lies in the fact that it simultaneously displays molecular size, shape as well as positive, negative, and neutral electrostatic potential region in terms of grading and is very useful in the investigation of molecular structure with its physiochemical property relationship 26-27. The MESP diagram is shown in Figure 4. Arrangement of occupied and unoccupied orbitals according to increasing energy value are shown in fig-2