Comparative Toxicity Assessment of Aluminum Sulfate and Plant-Based Alum Mordant Using Zebrafish (Danio rerio) Embryos

Since the genus Symplocos emerged as a flagship Al-hyperaccumulator plant, it has gained remarkable popularity among textile artisans. However, research on eco-friendly labels has become a priority. This study aims to investigate the in vivo toxicity level of using commercial aluminum sulfate mordant Al(SO) compared to the natural mordant from Symplocos fasciculata leaves, using zebrafish (Danio rerio, Hamilton 1882) embryos. At the early stage of development, 3 hours post fertilization (hpf), the eggs were exposed to Al(SO) solutions (0.025 g/L, 0.05 g/L, and 0.1 g/L) and Symplocos fasciculata solutions (5 g/L, 2.5 g/L, and 12.5 g/L). The parameters measured included somitogenesis, spontaneous movement, eyes area, body length, heart, survival, and hatching rate. Additionally, morphological alterations were monitored daily until 96 hpf. Furthermore, the effects of histological tissue damage and developmental alterations were assessed using hematoxylin and eosin staining method, as well as cartilage staining method. The results showed that commercial and plant-based alum mordants caused developmental delays in zebrafish, but at different levels. Al(SO) showed a significantly higher level of toxicity compared to Symplocos fasciculata. Treatment with Al(SO) induced phenotypic changes, a histological profile, and increased mortality, resulting in craniofacial cartilage deformities at higher concentrations. In contrast, the plant-based alum mordants maintained a significantly higher survival rate, even at higher concentrations. Although Symplocos fasciculata caused a dose-dependent hatching delay, severe morphological or histological problems were observed with the synthetic mordant. Symplocos fasciculata exhibited mild sublethal effects, primarily characterized by a delay in hatching. Thus, empirically, the Symplocos fasciculata mordant was shown to have a much safer toxicological profile than the Al(SO) mordant. The implication is that Symplocos fasciculata leaves have the potential to serve as an environmentally friendly alternative mordant in sustainable textiles. © 2026, Egyptian Society for the Development of Fisheries and Human Health. All rights reserved.