Antidepressant evaluation of Andrographis paniculata Nees extract and andrographolide in chronic unpredictable stress zebrafish model

Andrographis paniculata (A. paniculata) showed an anti-depressive effect in rodent models. Zebrafish has recently emerged as a worthy complementary translational model for antidepressant drug discovery study. This study investigates the anti-depressive effect of A. paniculata extract and andrographolide in the chronic unpredictable stress (CUS)- zebrafish model. Four groups of zebrafish (n = 10/group), i.e. control, CUS (stressed, untreated), CUS + A. paniculata (100 mg/L) and CUS + fluoxetine (0.01 mg/L) were assessed in open-field and social interaction tests, 24 h after treatment. After extract screening, behavioural and cortisol analysis of andrographolide (5, 25 and 50 mg/kg, i.p.) and fluoxetine (10 mg/kg, i.p.) were evaluated. Before the behavioural study, acute toxicity and characterization of A. paniculata extract using UHPLC-ESI-MS/MS were performed. A significant reduction in freezing duration was found in A. paniculata- (t-test, p = 0.0234) and fluoxetine-treated groups (t-test, p < 0.0001) compared to the CUS group. A significant increase in total distance travelled, and contact duration was observed only in the fluoxetine-treated group (t-test, p = 0.0007) and (t-test, p = 0.0207), respectively. A significant increase in highly mobile duration was observed in both treatment groups. Andrographolide (50 mg/kg, i.p.) acute treatment showed a significant reduction in freezing duration (p = 0.0042), duration in a dark area (p = 0.0338) and cortisol level (p = 0.0156) and increased total distance travelled (p = 0.0144). Twenty-six compounds were tentatively characterized by LC-MS/MS method, and andrographolide content is 0.042 μg/g. According to cortisol analysis, A. paniculata's LC₅₀ is 627.99 mg/L, while andrographolide's EC₅₀ was determined as 26.915 mg/kg. Further assessment of the cellular and molecular underpinnings of the anti-depressive effect of andrographolide is strongly recommended to evaluate the potential as an antidepressant.