has been traditionally used in Southeast Asia to treat various health conditions. This study evaluated the toxicity of leaf extracts obtained using 100% methanol through maceration (100%M) and ultrasonic-assisted (100%U) extractions. The acute toxicity of both extracts was assessed using zebrafish embryos, following OECD 236 guidelines. Both extracts revealed concentration dependent lethality and developmental defects. The 100%M exhibited greater toxicity (LC50 = 247.67 µg/mL) compared to the 100%U (LC50 = 395.26 µg/mL), with more severe impacts on hatchability, eye size, heartbeat and body length. At their lowest tested concentrations (31.25 µg/mL for 100%M and 200 µg/mL for 100%U), both extracts showed no lethal or sub lethal effects, indicating a threshold below which embryonic development remains unaffected. Q ToF LCMS analysis detected luteolin 7 rhamnosyl(1→6)galactoside, 6 hydroxyluteolin 5 rhamnoside, 8 hydroxyluteolin 8 glucoside, reserpic acid, methyl reserpate, 17-O-acetylajmaline and mitragynine which may underlie the toxicological effects associated with kratom leaves.
Begum et al. (2026) studied this question.