Toxicity assessment of Eucomis autumnalis and Merwilla plumbea using the in vivo zebrafish embryotoxicity test (ZET).

ETHNOPHARMACOLOGICAL RELEVANCE: Eucomis autumnalis (Mill.) Chitt. and Merwilla plumbea (Lindl.) Speta are popularly used in southern African healing practices to treat a wide range of diseases such as gastrointestinal, respiratory and skin conditions, as well as spiritual protectants against witchcraft. The pharmacological properties of the two species are well documented; however, studies that investigate the safety profiles using in vivo models are limited.

AIM OF THE STUDY: This study evaluated the toxicity profiles of the two plant species independently using the in vivo zebrafish embryotoxicity test (ZET).

MATERIALS AND

METHODS

The whole plant of E. autumnalis and the bulb of M. plumbea were extracted with methanol using ultrasonic-assisted extraction. Zebrafish embryos at 6 hours post-fertilisation (hpf) were placed in microtitre plates and treated with various concentrations of methanol extracts of the two plant species. The plates were incubated at 28.5 °C and embryos observed at 24, 48, 72, and 96 hpf on an inverted microscope mounted with a camera and a high-speed digital charge-coupled device (CCD). Acute toxicity (hatchability, survival rate and LC50 values), embryo activity (burst activity and burst count/min), cardiotoxicity (heart rate and blood flow), and morphological defects were monitored and activity videos analysed using DanioScope V1 software.

RESULTS

The ZET test demonstrated that both E. autumnalis and M. plumbea methanol extracts are embryotoxic with LC50 values of 9.7 μg/mL and 7.65 μg/mL, respectively. At higher concentrations, E. autumnalis (10-12 μg/mL) and M. plumbea (7 μg/mL - 10.5 μg/mL) increased burst activity and induced abnormalities in the yolk sac and swim bladder development. Eucomis autumnalis did not cause cardiotoxic effects at all the tested concentrations; however, M. plumbea treatment resulted in decreased heart rate at concentrations >9.5 μg/mL, indicating cardiotoxicity.

CONCLUSION

This study emphasises the importance of toxicological-related research on medicinal plants to ensure documentation of possible toxic effects.