RESUMO
ETHNOPHARMACOLOGICAL RELEVANCE: The plant, Ficus religiosa (L.) from the family Moraceae, has been extensively used in Ayurveda and Unani. Traditionally this plant is known for the treatment of constipation, liver diseases and neurological disorders that are related to hypothyroidism. AIM OF THE STUDY: This study was primarily designed to evaluate the effect of Ficus religiosa leaf (FL) extract in ameliorating hypothyroidism in rats and to identify the major bioactive compounds in the test extract that might be responsible for the thyroid-altering activity. In addition, the probable mechanism underlying the thyroid regulation of the main FL constituents were analyzed by molecular docking. MATERIALS AND METHODS: Adult female Wistar rats were used. LC-ESI-MS/MS was performed to identify the compounds present in the extract. HPLC analysis of FL extract was also performed. A pilot study was made using 3 doses of FL extract. Out of 50, 100, and 200 mg/kg, 100 mg/kg appeared to be the most effective one as it could increase thyroid hormones and decreased TSH levels. In the final experiment, propyl-thiouracil (PTU)-induced hypothyroid rats were orally treated with FL extract (100 mg/kg) or L-thyroxine (100 µg/kg, i.p.) daily for 28 consecutive days. On 29th day, all rats were sacrificed and the serum levels of triiodothyronine (T3), thyroxine (T4), thyrotropin (TSH), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and hepatic 5' deiodinase-1(5'D1) were estimated by ELISA. Liver marker enzymes (alanine aminotransferase, ALT and aspartate aminotransferase, AST); total cholesterol (TC) and triglycerides (TG); hepatic lipid peroxidation (LPO) and the activities of antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione (GSH) content were estimated in liver tissues. RESULTS: LC-MS-MS analyses of the leaf extract identified 11 compounds including the three major compounds, betulinic acid (BA), chlorogenic acid (CGA), and quinic acid (QA). While the PTU treatment decreased the levels of thyroid hormones and 5'D1 activity, it increased the TSH, ALT, AST, TNF-α, IL-6, TC, and TG levels. Furthermore, hepatic LPO significantly increased with a decrease in reduced GSH, SOD, CAT, and GPx. However, FL treatment in PTU-induced animals nearly reversed these adverse effects and improved liver function by decreasing ALT, AST, hepatic LPO and increasing the levels of antioxidants. FL not only improved the liver histology, but also suppressed the inflammatory cytokines, TNF-α and IL-6 in PTU-induced animals. A molecular docking study towards the understanding of the thyroid stimulatory mechanism of action revealed that BA, CGA, and QA might have augmented thyroid hormones by interacting with the thyroid hormone receptor (TRß1) and TSH receptor (TSHR). CONCLUSION: For the first time, we report the pro-thyroidal potential of Ficus religiosa leaf extract. We postulate that its main bioactive compounds, BA, CGA, and QA involved in this action may serve as novel thyroid agonists in ameliorating hypothyroidism.