Anticonvulsant activity and toxicity studies of hydroethanolic extract of pseudospondias microcarpa bark in zebrafish models

Background

Epilepsy is a major neurological disorder, and a substantial proportion of patients remain resistant to available antiseizure medicines or experience adverse effects. Medicinal plants therefore remain important sources of potential anticonvulsant agents. Pseudospondias microcarpa (A. Rich) Engl. has documented traditional medicinal use in the management of mental disorders such as anxiety, depression and epilepsy. While its leaves have previously demonstrated anti-seizure activity, evidence for the anticonvulsant and safety profiles of the stem bark is limited. This study therefore evaluated the anticonvulsant activity, acute toxicity, and developmental/teratogenic effects of the hydroethanolic extract of P. microcarpa stem bark using zebrafish models.

Methods

Fresh stem bark of P. microcarpa were collected from Ziavi, Volta Region, Ghana and was extracted by cold maceration with 70% ethanol and freeze-dried. Anticonvulsant activity was assessed in adult zebrafish using a pentylenetetrazol (PTZ)-induced seizure model. Fish were pretreated with the extract at 30, 100, and 300 μg/mL for 10 min before exposure to 20 mM PTZ. Carbamazepine (200 µm) and sodium valproate (5mM) served as positive controls. Locomotor activity was recorded and analysed using EthoVision XT software, with distance travelled and velocity used as behavioural indicators of seizure activity. Acute toxicity was assessed by determining the maximum tolerated concentration. Embryotoxicity and teratogenicity were evaluated using zebrafish embryos exposed to 1, 3, 10, 30, and 100 μg/mL for 96 h, with mortality, coagulation, heartbeat, somite formation, tail detachment, hatching, motility, and morphological abnormalities assessed at specified time points.

Results

The stem bark extract demonstrated anticonvulsant activity at all tested concentrations. The 300 μg/mL concentration produced the greatest reduction in seizure-associated locomotor activity, with a mean distance moved of 78.16 ± 17.35 cm (p < 0.0001), and the lowest total mean distance travelled of 810.0 cm (p = 0.0007). A concentration-dependent reduction in velocity was also observed, with the 300 μg/mL treatment producing a mean velocity of 2.02 ± 0.28 cm/s (p < 0.0001) and a total mean velocity of 2.74 ± 0.19 cm/s compared with 5.47 ± 0.38 cm/s in the PTZ-only group (p = 0.0048). In the embryo toxicity assay, no mortality or observable lethal or sublethal developmental effects occurred across the tested concentrations during 96 h of exposure. Embryos showed normal development, and treated groups achieved a 100% hatch rate at 48 hpf. No spinal curvature, failure to hatch, absence of heartbeat, tail non-detachment, or other morphological deformities were observed.

Conclusions

The hydroethanolic extract of P. microcarpa stem bark exhibits significant, concentration-dependent anticonvulsant activity in the PTZ-induced zebrafish model, as demonstrated by reductions in distance travelled and swimming velocity. Within the concentrations evaluated, the extract also showed no observable embryotoxic, lethal, or teratogenic effects during early zebrafish development. These findings provide preliminary preclinical evidence supporting the anticonvulsant potential and developmental safety of P. microcarpa stem bark and warrant further investigation to identify the bioactive constituents and elucidate the mechanisms underlying its antiseizure effects.

References

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