# Comparative Study of Condensed and Hydrolysable Tannins during the Early Stages of Zebrafish Development

## TL;DR

This study examines how different concentrations of plant-derived tannins affect zebrafish development and hatching.

## Contribution

The study identifies concentration thresholds of condensed and hydrolysable tannins that delay zebrafish hatching and downregulate hatching-related genes.

## Key findings

- Low concentrations of CTs and HTs (μg/L) showed no toxicity in zebrafish embryos.
- HTs at mg/L concentrations delayed hatching and downregulated hatching-related genes.
- CTs caused hatching delays mainly at mg/L concentrations.

## Abstract

In this study, we present data on the effects of condensed tannins (CTs) and hydrolysable tannins (HTs), polyphenols extracted from plants, at different concentrations on zebrafish development to identify the range of concentrations with toxic effects. Zebrafish embryos were exposed to CTs and HTs at two different concentration ranges (5.0–20.0 μgL−1 and 5.0–20.0 mgL−1) for 72 h. The toxicity parameters were observed up to 72 h of treatment. The uptake of CTs and HTs by the zebrafish larvae was assessed via HPLC analysis. A qRT-PCR analysis was performed to evaluate the expressions of genes cd63, zhe1, and klf4, involved in the hatching process of zebrafish. CTs and HTs at 5.0, 10.0, and 20.0 μgL−1 were not toxic. On the contrary, at 5.0, 10.0, and 20.0 mgL−1, HTs induced a delay in hatching starting from 48 h of treatment, while CTs showed a delay in hatching mainly at 48 h. The analysis of gene expression showed a downregulation in the group exposed to HTs, confirming the hatching data. We believe that this study is important for defining the optimal doses of CTs and HTs to be employed in different application fields such as the chemical industry, the animal feed industry, and medical science.