Diphyllin

Diphyllin is an orally active V-ATPase inhibitor (IC₅₀=17 nM) and HIV-1 inhibitor (IC₅₀=0.38 μM) . Diphyllin blocks the acidification of osteoclast lysosomes and bone resorption lacunas (IC₅₀=0.6 nM for acid influx inhibition)， thereby inhibiting bone resorption. Diphyllin can effectively inhibit osteoclast-mediated bone resorption and has no effect on osteoblastic bone formation. Diphyllin can be used in the research of bone metabolism-related diseases and has the potential to inhibit diseases related to excessive bone resorption^[1][2][3][4]. In Vitro:Acid Influx Assay: Diphyllin (0.6 nM; 30 min) potently inhibits acid influx in isolated vesicles from bovine adrenal medullae^[2]. V-ATPase Assay: Diphyllin (17 nM; 1 h) inhibits V-ATPase activity^[2]. Osteoclast Acidification Assay: Diphyllin (1 μM; 45 min) dose-dependently inhibits lysosomal acidification in human osteoclasts, and completely abolishes the orange signal at 1 μM^[2]. Resorption Assays: Diphyllin (14 nM; 5 days) dose-dependently inhibits human osteoclastic bone resorption, while increasing cell viability, tartrate-resistant acid phosphatase (TRACP) activity, and the number of calcitonin receptor-positive cells; Diphyllin (49 nM; 5 days) inhibits calcium release from bone slices during osteoclastic bone resorption; Diphyllin (29 nM; 5 days) dose-dependently decreases the resorbed bone area^[2]. Osteoblastogenesis Assay: Diphyllin (up to 100 nM; 21 days) shows no effect on bone formation and no cytotoxicity in the mouse osteoblastic cell line MC3T3-E1^[2]. Macrophage-related Assays: In LPS/IFN-γ-activated murine peritoneal macrophages, Diphyllin (12.5 μM; 24 h) inhibits NO production; Diphyllin (12.5-50 μM; 24 h) inhibits the production of TNF-α and IL-12; when macrophages are pre-activated with LPS/IFN-γ for 24 h, Diphyllin (50 μM; 24 h) still inhibits NO production^[3]. In Vivo:Diphyllin (20 mg/kg; oral; once a day; for 10 consecutive days) significantly inhibits the tumor growth of SGC7901 cells in mice, reduced tumor weight, downregulated the expression of V-ATPase in tumor tissues, and reduced the levels of MMP-2 and MMP-9 in serum^[4].