Molecular Docking Analysis of Selected Clinacanthus nutans Constituents as Xanthine Oxidase, Nitric Oxide Synthase, Human Neutrophil Elastase, Matrix Metalloproteinase 2, Matrix Metalloproteinase 9 and Squalene Synthase Inhibitors

BACKGROUND: Clinacanthus nutans (Burm. f.) Lindau has gained popularity among Malaysians as a traditional plant for anti-inflammatory activity. OBJECTIVE: This prompted us to carry out the present study on a selected 11 constituents of C. nutans which are clinacoside A–C, cycloclinacoside A1, shaftoside, vitexin, orientin, isovitexin, isoorientin, lupeol and β-sitosterol. MATERIALS AND METHODS: Selected 11 constituents of C. nutans were evaluated on the docking behavior of xanthine oxidase (XO), nitric oxide synthase (NOS), human neutrophil elastase (HNE), matrix metalloproteinase (MMP 2 and 9), and squalene synthase (SQS) using Discovery Studio Version 3.1. Also, molecular physicochemical, bioactivity, absorption, distribution, metabolism, excretion, and toxicity (ADMET), and toxicity prediction by computer assisted technology analyzes were also carried out. RESULTS: The molecular physicochemical analysis revealed that four ligands, namely clinacoside A–C and cycloclinacoside A1 showed nil violations and complied with Lipinski's rule of five. As for the analysis of bioactivity, all the 11 selected constituents of C. nutans exhibited active score (>0) toward enzyme inhibitors descriptor. ADMET analysis showed that the ligands except orientin and isoorientin were predicted to have Cytochrome P(450)2D6 inhibition effect. Docking studies and binding free energy calculations revealed that clinacoside B exhibited the least binding energy for the target enzymes except for XO and SQS. Isovitexin and isoorientin showed the potentials in the docking and binding with all of the six targeted enzymes, whereas vitexin and orientin docked and bound with only NOS and HNE. CONCLUSION: This present study has paved a new insight in understanding these 11 C. nutans ligands as potential inhibitors against XO, NOS, HNE, MMP 2, MMP 9, and SQS. SUMMARY: Isovitexin and isoorientin (Clinacanthus nutans constituent) showed potentials in the docking and binding with all of the six targeted enzymes (xanthine oxidase [XO], nitric oxide synthase [NOS], human neutrophil elastase [HNE], matrix metalloproteinase [MMP 2 and 9], and squalene synthase [SQS]). Moreover, clinacoside B (C. nutans constituent) exhibited the least binding energy for the target enzymes except for XO and SQS. Interestingly, all of the selected ligands from C. nutans showed the potential to dock and bind with HNE. Abbreviations used: C. nutans: Clinacanthus nutans, XO: Xanthine oxidase, NOS: Nitric oxide synthase, HNE: Human neutrophil elastase, MMP: Matrix metalloproteinase, SQS: Squalene synthase, ADMET: Absorption, Distribution, Metabolism, Excretion, and Toxicity, TOPKAT: Toxicity prediction by the computer assisted technology