hellebrigenin

Cytotoxic profile of natural and some modified bufadienolides from toad Rhinella schneideri parotoid gland secretion[Reference: WebLink]

Toxicon, 2010, 56(3):339-348.

Cutaneous secretions of toad species are an important source of bufadienolides, compounds that exhibit interesting structural features and biopharmacological properties.
METHODS AND RESULTS:
Here we describe the isolation of bufadienolides from the Brazilian toad Rhinella schneideri parotoid glands secretion, including: marinobufagin (1), bufalin (2), telocinobufagin (3), Hellebrigenin (4), and the atypical 20S,21R-epoxymarinobufagin (5) besides the widespread β-sitosterol (6). Starting from natural bufadienolides four derivatives were prepared: 3β-acetoxy-marinobufagin (7), 3β-acetoxy-bufalin (8), 3β-acetoxy-telocinobufagin (9), and 3β-acetoxy-20S,21R-epoxymarinobufagin (10).
CONCLUSIONS:
The cytotoxic evaluation showed that all natural bufadienolides and their derivatives exhibited moderate to strong activity against human HL-60, SF-295, MDA-MB-435, and HCT-8 cancer cell strains without hemolysis of mouse erythrocytes. The acetylated bufadienolides (7–9) and the epoxide 10 showed lesser peripheral blood lymphocytes (PBLs) inhibitory activity than their precursors, suggesting that chemical modifications on such compounds can play an important role on the modulation of their cytotoxic profile.

Hellebrigenin induces cell cycle arrest and apoptosis in human hepatocellular carcinoma HepG2 cells through inhibition of Akt.[Pubmed: 24954031]

Chem Biol Interact. 2014 Aug 5;219:184-94.

Hellebrigenin, one of bufadienolides belonging to cardioactive steroids, was found in skin secretions of toads and plants of Helleborus and Kalanchoe genera.
METHODS AND RESULTS:
In searching for natural constituents with anti-hepatoma activities, we found that Hellebrigenin, isolated from traditional Chinese medicine Venenum Bufonis, potently reduced the viability and colony formation of human hepatocellular carcinoma cells HepG2, and went on to explore the underlying molecular mechanisms. Our results demonstrated that Hellebrigenin triggered DNA damage through DNA double-stranded breaks and subsequently induced cell cycle G2/M arrest associated with up-regulation of p-ATM (Ser(1981)), p-Chk2 (Tyr(68)), p-CDK1 (Tyr(15)) and Cyclin B1, and down-regulation of p-CDC25C (Ser(216)). It was also found that Hellebrigenin induced mitochondrial apoptosis, characterized by Bax translocation to mitochondria, disruption of mitochondrial membrane potential, release of cytochrome c into cytosol and sequential activation of caspases and PARP. In addition, Akt expression and phosphorylation were inhibited by Hellebrigenin, whereas Akt silencing with siRNA significantly blocked cell cycle arrest but enhanced apoptosis induced by Hellebrigenin. Activation of Akt by human insulin-like growth factor I (hIGF-I) could obviously attenuate Hellebrigenin-induced cell death.
CONCLUSIONS:
In summary, our study is the first to report the efficacy of Hellebrigenin against HepG2 and elucidated its molecular mechanisms including DNA damage, mitochondria collapse, cell cycle arrest and apoptosis, which will contribute to the development of Hellebrigenin into a chemotherapeutic agent in the treatment of liver cancer.