Effect of Parquetina nigrescens (Afzel.) Leaves on Letrozole-Induced PCOS in Rats: a Molecular Insight into Its Phytoconstituents.

Polycystic ovarian syndrome (PCOS) is one of the common causes of female infertility in women of reproductive age. P. nigrescens is a plant used in the treatment of various diseases including menstrual disorders. This study investigated the effect of ethanolic extracts of P. nigrescens leaves on the estrous cycle, fasting blood glucose, and hormonal and lipid profile in letrozole-induced PCOS rats and also evaluated the molecular mechanism of the active constituents using computational methods. After the induction of PCOS with letrozole, rats were treated orally for 14 days with distilled water (1 mg/kg/day), clomiphene citrate (2 mg/kg/day), metformin (7.14 mg/kg/day), and ethanolic extract of P. nigrescens (50 and 100 mg). Thereafter, selected biochemical parameters were assayed to determine the extract's effect on the estrous cycle. Molecular docking and molecular dynamics simulation (MDS) were carried out to determine the binding affinity and relative stability of the ligand-receptor complexes. Letrozole-induced PCOS rats showed irregular estrous cyclicity, elevated (p > 0.05) triglycerides, low-density lipoprotein cholesterol (LDL), total cholesterol, insulin, testosterone, and luteinizing hormone (LH) concentration, low (p > 0.05) progesterone, low follicle-stimulating hormone (FSH), high-density lipoprotein cholesterol (HDL), and high fasting blood glucose concentration compared to that of the control group. The reproductive, biochemical, and structural alterations were reversed by the administration of ethanolic extract of P. nigrescens leaves (50 mg/kg) which restored the estrous cycle after 14 days of treatment. However, the ethanolic extracts of P. nigrescens (100 mg/kg) significantly increased (p > 0.05) FSH, HDL, and progesterone concentrations but decreased the LH, progesterone, and total cholesterol. Of all 44 compounds identified in GCMS analysis of an ethanolic extract of P. nigrescens leaves, only 2-ethylbutyl heptyl ester (CID 91705405) had a higher binding affinity for hormonal receptors and enzymes responsible for hepatic gluconeogenesis compared to standard drugs used in the study. CID 91705405 was also relatively stable over 100 ns of MDS. This compound is therefore revealed to have the potential to modulate both endocrine and metabolic pathways involved in PCOS. The ethanolic extract of P. nigrescens leaves can therefore be considered in the management/treatment of the reproductive and metabolic disorders related to PCOS subject to further experimental validation.