Pharmacological investigation of <i>Hamelia patens</i> leaves for central nervous system activity in rats

Objectives: The present study was undertaken to investigate the antioxidant and anxiolytic potential of the ethanolic leaf extract of Hamelia patens (EEHP) and its acetone-enriched fraction (AEHP) using in vitro antioxidant assays, in vivo central nervous system (CNS) screening models in Wistar albino rats and in silico docking studies. Materials and Methods: Leaves of H. patens were subjected to extraction with ethanol by maceration to yield the EEHP, followed by fractionation using acetone to obtain the AEHP. Preliminary qualitative phytochemical screening was carried out to identify major phytoconstituents. In vitro antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide free radical scavenging assays. Anxiolytic activity was assessed using the Elevated Plus Maze, Light and Dark Model, Mirror Chamber Apparatus and spontaneous locomotor activity using the Opto-Varimex Autotrack system. EEHP and AEHP were administered orally at doses of 100 mg/kg and 200 mg/kg for a duration of 7 days. Diazepam was used as the standard drug. Data were statistically analysed using one-way analysis of variance followed by Dunnett’s test. The phytoconstituents present in H. patens were docked against the GABAA-BZD receptor in silico . Results: Phytochemical screening revealed the presence of flavonoids, alkaloids, carbohydrates, proteins, glycosides, tannins and triterpenoids in both EEHP and AEHP. Both extracts demonstrated concentration-dependent free radical scavenging activity in DPPH and nitric oxide assays. In the Elevated Plus Maze, treatment with EEHP and AEHP resulted in a significant increase in percentage open arm entries and percentage time spent in open arms compared to the control. In the Light and Dark Model, the number of entries into the light compartment and time spent in the light compartment were significantly increased. The Mirror Chamber Apparatus showed a significant increase in the number of entries and time spent in the Mirror Chamber. Spontaneous locomotor activity assessment demonstrated a significant increase in resting time compared to the control. In silico molecular docking studies of the phytoconstituents of H. patens exhibited profound receptor binding interactions. Conclusion: The findings of the study indicate that H. patens leaf extracts possess significant antioxidant and anxiolytic activity, supporting their traditional use in CNS-related disorders. Furthermore, the phytoconstituents with GABAA-BZD receptor in silico demonstrated strong binding affinities, indicating a possible mechanism underlying their anxiolytic action. The observed effects may be attributed to the presence of bioactive flavonoids and phenolics.