Regulation of melanin production via the MC1R signaling pathway is a protective mechanism of the skin of living organisms against exposure to ultraviolet rays. The discovery of human skin-whitening agents has been one of the most intense pursuits of the cosmetic industry. The MC1R signaling pathway is activated by its agonist, alpha-melanocyte stimulating hormone (α-MSH), and mainly regulates melanogenesis. Here, we evaluated the antimelanogenic activities of curcumin (CUR) and its two derivatives, dimethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC), in B16F10 mouse melanoma cells and zebrafish embryos. CUR and BDMC reduced the α-MSH-induced melanin production in B16F10 cells and also downregulated the expression of the melanin-production-related genes Tyr, Mitf, Trp-1, and Trp-2. Moreover, the biological activity of these two compounds against melanogenesis was confirmed in in vivo experiments using zebrafish embryos. However, the highest concentration of CUR (5 µM) resulted in slight malformations in zebrafish embryos, as indicated by acute toxicity tests. In contrast, DMC did not show any biological activity in vitro or in vivo. Conclusively, BDMC is a strong candidate as a skin-whitening agent.

Pymetrozine (PYM) is worldwide used to control sucking insect pests in rice-cultivated fields and it is degraded into various metabolites including 3-pyridinecarboxaldehyde (3-PCA). These two pyridine compounds were used to determine their impacts on aquatic environments, particularly on the aquatic animal model zebrafish (Danio rerio). PYM did not show acute toxicities in terms of lethality, hatching rate, and phenotypic changes in zebrafish embryos in the tested ranges up to a concentration of 20 mg/L. 3-PCA exhibited acute toxicity with LC₅₀ and EC₅₀ values of 10.7 and 2.07 mg/L, respectively. 3-PCA treatment caused phenotypic changes including pericardial edema, yolk sac edema, hyperemia, and curved spine, at a concentration of 10 mg/L after 48 h of exposure. Abnormal cardiac development was observed in 3-PCA-treated zebrafish embryos at a concentration of 5 mg/L with reduced heart function. In a molecular analysis, cacna1c, encoding a voltage-dependent calcium channel, was significantly down-regulated in the 3-PCA-treated embryos, indicating synaptic and behavioral defects. Hyperemia and incomplete intersegmental vessels were observed in 3-PCA-treated embryos. Based on these results, it is necessary to generate scientific information on the acute and chronic toxicity of PYM and its metabolites with regular monitoring of their residues in aquatic environments.

Pyrochar (Biochar) produced from the thermochemical conversion of biomass has been widely used as a soil amendment to improve agricultural soil quality. Since polycyclic aromatic hydrocarbons (PAHs) can be produced in such processes, the occurrence of PAHs in pyrochars has been extensively studied, and standards such as the European Biochar Certificate (EBC) and International Biochar Initiative (IBI) contain limit values for biochars applied to soils. However, studies on PAH levels in hydrochars from hydrothermal processes, which can be an alternative to wet biomass are scarce. This study focuses on comparing the occurrence of 16 PAHs regulated by the US EPA in 22 char samples (including pyrochars from pyrolysis, hydrochars from hydrothermal carbonization, and, for the first time, hydrothermal humification) using an ultrasonic extraction method. Results showed that the sum of the 16 EPA PAHs in all samples was well below the requirements of the two standards, except for pyrochar produced at the farm scale. They ranged from 131 to 9358 µg·kg⁻¹ in the seven pyrochars and from not detected to 333 µg·kg⁻¹ for the fourteen hydrochars. Our findings indicate that hydrochar produced via hydrothermal methods exhibits much lower concentrations and is a safe option for soil amendment and environmental applications.

Piperlongumine (PL) and piperine (PP) are alkaloids presented in long pepper (Piper longum), and they exhibit various biological activities, especially anti-cancer properties. With these regards, they are considered as future medicines with high potential. Even they are exposed to humans such a long time, their potential toxicities in the environment have not been studied. Therefore, their ecological toxicities were assessed using zebrafish embryos. PP showed low mortality and no abnormal phenotype up to 10 µM. However, PL exhibited strong acute toxicity at the concentration of 5-10 µM ranges, and abnormal development were frequently found in the range of 1-2.5 µM with pericardial and yolk sac edemas. In transgenic zebrafish embryos, PL induced an increase in the number of intersegmental vessels and delayed the early-stage development. PL treatment affected heart formation and heart rate. The presence of PL induced the expression of cytokines, inflammatory markers, and inflammasome in the embryos. The PL treatment changed the mRNA levels of the ER stress and apoptosis-related genes. In addition, ROS production was observed during early-stage development of PL-treated zebrafish embryos. These results indicate that developing PL as a medicine would require extremely meticulous strategies to prevent potential toxicity.