Kelulut honey (KH) is a type of honey with various pharmacological properties that can be found in Malaysia. Nevertheless, the safety aspects of this honey have not been adequately addressed. This study evaluated the developmental toxicity of KH from Trigona sp on zebrafish (Danio rerio) embryos. Viable zebrafish embryos at 3 hours post fertilization (hpf) (early stage) and 24 hpf (organ development stage) were treated with KH (1 to 20 mg/mL). The embryos were examined for morphological abnormalities and viability until 96 h of KH treatment. Coagulated embryos were identified after treatment with KH (≥10 mg/mL) for 3 hpf group and KH (≥12 mg/mL) for 24 hpf group. The LC 50 values of KH at 96 h of exposure for the 3 hpf and 24 hpf group were 12.52 and 16.36 mg/mL, respectively. The maximum allowable concentration (MAC) for KH on 3 hpf and 24 hpf group were 0.63 and 0.82 mg/mL, respectively. The irregular cardiac rate of the embryos was noted at 10 mg/mL for 3 hpf group and 13 mg/mL of KH for 24 hpf group. In summary, the early stage embryo (3 hpf group) was more sensitive to KH than the one of later stage (24 hpf group). It indicates that serious precautions should be taken into account in the use of any material including natural product, be it food or supplement, especially in the early stage of life.
Large doses of ionizing radiation can damage human tissues. Therefore, there is a need to investigate the radiation effects as well as identify effective and non-toxic radioprotectors. This study evaluated the radioprotective effects of Kelulut honey (KH) from stingless bee (Trigona sp.) on zebrafish (Danio rerio) embryos. Viable zebrafish embryos at 24 hpf were dechorionated and divided into four groups, namely untreated and non-irradiated, untreated and irradiated, KH pre-treatment and amifostine pre-treatment. The embryos were first treated with KH (8 mg/mL) or amifostine (4 mM) before irradiation at doses of 11 Gy to 20 Gy using gamma ray source, caesium-137 (137Cs). Lethality and abnormality analysis were performed on all of the embryos in the study. Immunohistochemistry assay was also performed using selected proteins, namely γ-H2AX and caspase-3, to investigate DNA damages and incidences of apoptosis. KH was found to reduce coagulation effects at up to 20 Gy in the lethality analysis. The embryos developed combinations of abnormality, namely microphthalmia (M), body curvature and microphthalmia (BM), body curvature with microphthalmia and microcephaly (BMC), microphthalmia and pericardial oedema (MO), pericardial oedema (O), microphthalmia with microcephaly and pericardial oedema (MCO) and all of the abnormalities (AA). There were more abnormalities developed from 24 to 72 h (h) post-irradiation in all groups. At 96 h post-irradiation, KH was identified to reduce body curvature effect in the irradiated embryos (up to 16 Gy). γ-H2AX and caspase-3 intensities in the embryos pre-treated with KH were also found to be lower than the untreated group at gamma irradiation doses of 11 Gy to 20 Gy and 11 Gy to 19 Gy, respectively. KH was proven to increase the survival rate of zebrafish embryos and exhibited protection against organ-specific abnormality. KH was also found to possess cellular protective mechanism by reducing DNA damage and apoptosis proteins expression.
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