Butein

Skin cancer incidence has drastically increased, causing a significant impact on global health. Increased UV radiation, along with changes in genetic and environmental factors, triggers the uncontrolled proliferation of skin cells. To address the increasing incidence of skin cancer, the discovery of novel treatment strategies is crucial. Natural products are one of the promising and alternative approaches for the treatment of skin cancer, which helps to mitigate the growing global health burden. Butein, naturally present in many plant families, demonstrates significant pharmacological properties, including anticancer activity. It inhibits the metastatic behavior in mouse melanoma cells; however, its effect on human skin carcinoma cell lines remains unexplored. Thus, this study investigates the anticancer potential of butein on skin carcinoma by employing different cytotoxicity assays such as Sulphorhodamine B (SRB), Neutral Red Uptake (NRU), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Further, cell-based assays and molecular interaction studies were performed to explore the inhibitory potential of butein on lipoxygenase-5 (LOX-5) and hyaluronidase, prominent cancer markers. Further investigation revealed that butein arrests cell cycle progression, increases reactive oxygen species (ROS) generation, and disrupts the mitochondrial membrane potential (MMP), leading to both apoptotic and necrotic cell death. In addition, butein possesses good oral bioavailability, drug-like properties, and high gastrointestinal absorption in prediction studies, while it did not alter human erythrocytes' integrity in an ex vivo study, suggesting it is a possible candidate for future trials.

A novel O-methyltransferase, LeOMT4, from Lentinula edodes was identified, expressed, and characterized. Although its catalytic activity was lower than that of the previously reported LeOMT2, LeOMT4 displayed strong regioselectivity for the meta-hydroxy group across different catecholic compounds, producing e.g., ferulic acid with an almost exclusive regioisomeric ratio of 98:2 and homoeriodictyol with a ratio of 82:18 (3'-product:4'-product). Leveraging the high sequence and predicted structural similarity between LeOMT2 and LeOMT4, key sites for the tailoring of LeOMT2 were identified through site-directed mutagenesis. This approach aimed for robust mutants retaining the high specific activity of LeOMT2, while enhancing regioselectivity. A single amino acid substitution, F182Y, enabled a regioisomeric ratio of 91:9 for the production of homoeriodictyol. Notably, another single amino acid substitution, I53M reversed the regioselectivity to 2:98 in favor of hesperetin. This strategy enables the selective production of sought-after pharmacologically active flavonoids (butein) and flavor-active flavonoids (homoeriodictyol, hesperetin, hesperetin dihydrochalcone).