## 3 Results and Discussion
### Docking Studies  
Fluorescence studies revealed the binding properties of kiwifruit and persimmon water extracts with HSA. To delineate the mechanisms at a molecular level, 15 compounds identified from kiwifruit and persimmon extracts were analyzed through docking studies. Ligands exhibiting high binding affinity towards HSA are shown in Figure 3. Caffe acid, quinic acid, catechol, syringic acid, hesperidin and quercetin were identified to be the major ingredients [1; 5; 39] that are common among the three varieties of kiwifruit ('Hayward', 'Bidan' and 'Cheongsan') used in the current study (Table 3). From the interaction analysis, hesperidin and quercetin were identified as the top scorers among the compounds screened from the kiwifruit. Hesperidin was found to have a docking and binding energy score of \(-168.71\) and \(-140.3\) kcal/mol, respectively. Whereas, quercetin exhibited the highest dock score of \(-163\) and binding energy score of \(-116.8\) kcal/mol. Hesperidin (Figure 4) formed five conventional hydrogen bond interactions with three residues (Leu115, Arg117 and Leu185). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**S. No**} & \multirow{2}{*}{**PubChem ID**} & \multirow{2}{*}{**Compounds**} & \multicolumn{4}{c}{**HSA + Kiwifruit**} \\ \cline{4-7}  & & & **BE** & **DS** & **VDW** & **HB** \\ \hline
1 & 5280863 & Kaempfer & \(-106.3\) & \(-138.14\) & \(-102.8\) & \(-3.4\) \\
2 & 5280805 & Rutin & \(-78.9\) & \(-82.84\) & \(-61.9\) & \(-16.9\) \\
3 & 689043 & Caffeic acid & \(-75.0\) & \(-99.36\) & \(-71.5\) & \(-3.5\) \\
4 & 6508 & Quinic acid & \(-69.4\) & \(-95.18\) & \(-63.0\) & \(-6.3\) \\
5 & 289 & Catechol & \(-50.8\) & \(-61.67\) & \(-47.3\) & \(-3.4\) \\
6 & 10742 & Springic acid & \(-0.5\) & \(-107.18\) & \(-77.2\) & \(-3.2\) \\
7 & 10621 & Hesperidin & \(-140.3\) & \(-168.71\) & \(-126.1\) & \(-14.1\) \\
8 & 5280343 & Quercetin & \(-116.8\) & \(-163\) & \(-106.2\) & \(-10.5\) \\
9 & 72 & Protocatechuic acid & \(-69.0\) & \(-90.03\) & \(-66.2\) & \(-2.7\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The ligands from kiwifruit showing interaction with HSA represented with binding energy (BE), dock score (DS), van der Waals (VDW) and H-bond (HB) energy. Figure 2: Three-dimensional fluorescence (3D-FL) spectra of interaction of human serum albumin (HSA) with polyphenols water extracts of kiwifruit and persimmon (**A–C**): HSA in water; HSA+Hayward’, HSA +Fuyu  
Figure 4: The interactions of the highest docking score ligands from different cultivars of kiwifruit and persimmon with HSA receptor protein. (**A**) hesperidin; (**B**) quercetin; (**C**) kaempfer; (**D**) protocatechic acid (3,4-dihydroxybenzoic acid). 2D view of ligands and their bonding type are represented in (**E–H**). Figure 3: Top scoring ligands (stick model) showing interactions with the receptor binding site of human serum albumin (space filling model). In addition, a carbon-hydrogen bond interaction with Pro113 and a pi-donor hydrogen bond interaction with Tyr161 and Gly189 were exhibited. Other key interactions include pi-sigma (Ile142), pi-alkyl and alkyl interactions (Tyr138, Pro118 and Leu115). Quercetin formed three hydrogen bond interactions with Leu135 and Arg117 and one carbon-hydrogen bond and pi-donor hydrogen bond interaction with Tyr138. It formed van der Waals interaction with Leu135 and other stabilizing interactions such as pi-pi stacked (Tyr161), amide-pi stacked (Tyr161) and pi-alkyl interactions (Ala158, Ile142 and Leu182). Kaempfer and rutin are the major compounds reported only in 'Hayward' and 'Bidan' and not in _Actinidia arguta_. Kaempfer and rutin have a dock score of \(-\)138.14 and \(-\)82.84 and binding energy of \(-\)106.3 and \(-\)78.9, respectively. Among the ligands, rutin has the highest hydrogen bond energy of \(-\)16.9 kcal/mol on interactions with the receptor protein HSA.