Antioxidant activity and in-silico evaluation of natural compounds of Carissa carandas as potential inhibitors of Gamma-Glutamyl Transpeptidase to enhance the efficacy of chemotherapy drugs against prostate cancer.

Gamma-glutamyl transferase (GGT) is a membrane-bound enzyme that notably, contributes to glutathione metabolism. Pro-oxidation and pro-inflammatory studies of GGT have been associated to a higher risk of various cancer types, which elicits tumor progression, growth acceleration, and the emergence of malignant characteristics such as drug resistance and metastasis. This study investigates the structural inhibition potential of identified bioactive compounds of Carissa carandas against GGT, which could increase drug efficacy and hence increase the therapeutic ability of chemotherapy for prostate cancer. In this present study, we evaluated various compounds in methanolic extracts of Carissa carandas plants with GC-MS analysis, analysed its antioxidant potential in-vitro, and performed in silico study of 22 major bioactive compounds identified by GC-MS to check their efficacy for inhibition of GGT using the pharmacoinformatic approach. The initial filtering of constituting compounds was performed with "Lipinski's rule", which analysed their drug-likeness. Moreover, molecular docking (MD) was used to screen inhibitors of GGT (PDB ID: 4GDX), which have pharmaceutical significance to boost tumor therapeutic efficacy. Our results stated that compounds such as valtrate, 4bromobenzenesulfono-2-naphthamide and acetamide have potent binding energies of -10.3, -9.45, and - 8.82 kcal/mol with target protein, respectively. Eventually, valtrate which showed the lowest binding energy at the active site residues of GGT was assessed via molecular dynamics (MD) simulation of 100 ns. The simulation trajectory, RMSD, Rg variations versus time and RMSF versus residue and SASA analysis in triplicates displayed effective and stable interactions between GGT and valtrate. Further, this in silico findings were validated via in vitro experiments against LNCaP cell lines using leaf extract as well as pure valtrate. MTT test was evaluated for cytotoxicity. The methanolic leaf extract of C. carandas showed best activity in comparison to flower, root & combined, with an IC value of 377.01 μg/ml. Valtrate reduced LNCaP cell viability in a concentration-dependent manner with IC value of 18.78 μM. According to our findings, valtrate exhibits great promise as a GGT inhibitor and could be used for the treatment of prostate cancer patients; nevertheless, clinical investigation is needed before its application.