Structures and bioactivities of seven flavonoids from Osmanthus fragrans 'Jinqiu' essential oil extraction residues.

Osmanthus fragrans are well-known for their fragrance, but it is wasteful if to discard O. fragrans flower after extracting their essential oils. In this paper, we found that O. fragrans flower residues were rich in flavonoids. Six flavonoids and one phenylethanoid glycoside were isolated from the ethanol extract of O. fragrans flower residues, identified as quercetin (1), rutin (2), verbascoside (3), genistin (4), kaempferol (5), isorhamnetin (6) and naringin (7). In bioactivity study, kaempferol (IC50 = 1.43 µg/mL) showed the best anti-inflammatory activity. Isorhamnetin, quercetin, kaempferol, verbascoside and rutin (the values of IC50 were 18.30, 11.05, 16.88, 20.21 and 22.76 µg/mL, respectively) showed excellent DPPH free radical scavenging activity. Verbascoside performed relatively well at inhibiting the growth of both CT26 colonic carcinoma cells (IC50 = 46.87 µg/mL) and HepG2 hepatocarcinoma cells (IC50 = 30.58 µg/mL). In addition, quercetin and kaempferol showed strong anti-proliferation activity against HepG2 cells.

Plant cyclopeptide RA-V kills human breast cancer cells by inducing mitochondria-mediated apoptosis through blocking PDK1-AKT interaction.

In the present paper, we examined the effects of a natural cyclopeptide RA-V on human breast cancer cells and the underlying mechanisms. RA-V significantly inhibited the growth of human breast cancer MCF-7, MDA-MB-231 cells and murine breast cancer 4T1 cells. In addition, RA-V triggered mitochondrial apoptotic pathway which was indicated by the loss of mitochondrial membrane potential, the release of cytochrome c, and the activation of caspase cascade. Further study showed that RA-V dramatically inhibited phosphorylation of AKT and 3-phosphoinositide dependent protein kinase 1 (PDK1) in MCF-7 cells. Moreover, RA-V disrupted the interaction between PDK1 and AKT in MCF-7 cells. Furthermore, RA-V-induced apoptosis could be enhanced by phosphatidylinositol 3-kinase inhibitor or attenuated by over-expression of AKT in all the three kinds of breast cancer cells. Taken together, this study shows that RA-V, which can induce mitochondria-mediated apoptosis, exerts strong anti-tumor activity against human breast cancer. The underlying anti-cancer mechanism of RA-V is related to the blockage of the interaction between PDK1 and AKT.