Screening of anti-melanoma compounds from Morus alba L.: Sanggenon C promotes melanoma cell apoptosis by disrupting intracellular Ca2+homeostasis

Ethnopharmacological relevance: Morus alba L. is a widespread plant that has long been considered to have remarkable medical values, including anti-inflammation in Traditional Chinese Medicine (TCM). The components of Morus Alba L. constituents have been extensively studied and have been shown to have high prospects for cancer therapy. However, limited investigations have been done on the bioactive compounds in Morus alba L. Aim of the study: This study aimed to systematically examine the anticancer properties of 28 commercially available compounds from Morus alba L. against melanoma cells in vitro. Additionally, the anticancer mechanisms of the bioactive compound exhibiting the most significant potential were further studied. Materials and methods: The anti-proliferative effects of Morus alba L.-derived compounds on melanoma cells were determined by colony formation assays. Their effects on cell viability and apoptosis were determined using the CCK8 assay and flow cytometry, respectively. The binding affinity of identified Morus alba L. compounds with anticancer activities towards melanoma targets was analyzed via molecular docking. The molecular mechanism of Sanggenon C was explored using soft agar assays, EdU incorporation assays, flow cytometry, western blotting, transcriptome analysis, and xenograft assays. Results: Based on colony formation assays, 11 compounds at 20 mu M significantly inhibited colony growth on a panel of melanoma cells. These compounds displayed IC50 values (half maximal inhibitory concentrations) ranging from 5 mu M to 30 mu M. Importantly, six compounds were identified as novel anti-melanoma agents, including Sanggenon C, 3 '-Geranyl-3-prenyl-2 ',4 ',5,7-tetrahydroxyflavone, Moracin P, Moracin O, Kuwanon A, and Kuwanon E. Among them, Sanggenon C showed the most potent effects, with an IC50 of about 5 mu M, significantly reducing proliferation and inducing apoptosis in melanoma cells. Based on the xenograft model assay, Sanggenon C significantly inhibited melanoma cell proliferation in vivo. Sanggenon C triggered ER stress in a dose-dependent manner, which further disrupted cellular calcium ion (Ca2+) homeostasis. The Ca2+ chelator BAPTA partially restored cell apoptosis induced by Sanggenon C, confirming that Ca2+ signaling contributed to the anticancer activity of Sanggenon C against melanoma. Conclusions: In our study, 11 compounds demonstrated anti-melanoma properties. Notably, Sanggenon C was found to promote apoptosis by disrupting the intracellular calcium homeostasis in melanoma cells. This study provides valuable information for the future development of novel cancer therapeutic agents from Morus alba L.