4-hydroxylonchocarpin and 6-prenylapigenin

Naturally occurring flavonoids have been reported to possess antimicrobial activity against a wide range of pathogens. However, the antimicrobial action mechanism of these compounds has not yet been elucidated. This study investigated the mechanism underlying the antibacterial activity of four flavonoids: 6,8-diprenyleriodictyol (1), isobavachalcone (2), 6-prenylapigenin (3) and 4-hydroxylonchocarpin (4). In addition, the toxicity of these compounds was evaluated. Determination of the minimum inhibitory concentrations (MICs) was performed by microbroth dilution method. Radiolabeled thymidine, uridine, and methionine were used to evaluate the effect of the compounds on the biosynthesis of DNA, RNA, and proteins while the sensitive cyanine dye DiS-C3-(5) (3,3'-dipropylthiadicarbocyanine iodide) was used for the effect on membrane potential. Bactericidal/bacteriolysis activities were performed by time-kill kinetic method. In the toxicity study, the numbers of survivors was recorded after injection of compounds into the hemolymph of silkworm larvae. Compounds showed significant antibacterial activity against Staphylococcus aureus including methicillin-resistant S. aureus (MRSA) strains with MICs values ranged between 0.5-128 μg/mL. Depolarization of membrane and inhibition of DNA, RNA, and proteins synthesis were observed in S. aureus when treated with those flavonoids. At 5-fold minimum inhibitory concentration, compounds reduced rapidly the bacterial cell density and caused lysis of S. aureus. Compounds 1, 2, and 4 did not show obvious toxic effects in silkworm larvae up to 625 μg/g of body weight. Flavonoids from Dorstenia species, 6,8-diprenyleriodictyol, isobavachalcone, and 4-hydroxylonchocarpin are bactericidal compounds. They cause damage of cell membrane, leading to the inhibition of macromolecular synthesis. Taking into account the in vivo safety and their significant antimicrobial potency, these flavonoids are promising leads for further drug development.

Topics: Animals; Anti-Infective Agents; Bombyx; Candida; Chalcones; Cryptococcus neoformans; DNA, Bacterial; Flavones; Flavonoids; Membrane Potentials; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Moraceae; Protein Biosynthesis; RNA, Bacterial; Staphylococcus aureus

Several flavonoid-like compounds were found to possess good antiproliferative properties. Herein, we examined the ability of four naturally occuring and biologically active flavonoids from the genus Dorstenia, gancaonin Q (1), 6-prenylapigenin (2), 6,8-diprenyleriodictyol (3), and 4-hydroxylonchocarpin ( 4), to inhibit the proliferation of a panel of fourteen cancer cell lines including leukemia and solid cancer cells, as well as AML12 normal hepatocytes. The study was extended to the analysis of cell cycle distribution, apoptosis induction, and caspase 3/7 activity and the antiangiogenic properties of the four compounds. The results of the cytotoxicity assays showed that more than 50 % inhibition of proliferation was obtained with compound 1 on all the fourteen studied cancer cell lines, with IC (50) values below 20 µg/mL. Compounds 2, 4, and 3 showed selective activity, with IC (50) values below 20 µg/mL being noted on 57.15 %, 71.42 %, and 85.71 % of the fourteen cancer cell lines, respectively. None of the compounds exhibited more than 50 % inhibition against AML12 normal hepatocytes cells at 20 µg/mL. IC (50) values below or around 4 µg/mL were recorded on 28.57 % of the tested cell lines for both compound 1 and 4 and 21.43 % for compound 3, which appeared to be the best cytotoxic compounds. This study indicates that caspase 3/7 activation is one of the modes of induction of apoptosis for compounds 1, 3, and 4 in CCRF-CEM cells. The results of the antiangiogenic assay indicated that compounds 1, 3, and 4 were also able to inhibit the growth of blood capillaries on the chorioallantoic membrane of quail eggs, the best effect being noted for compound 4 (54.1 % inhibition). The results of the present work provide evidence of the cytotoxic potential of the four studied flavonoids and supportive data for further investigations.

Topics: Angiogenesis Inhibitors; Animals; Antineoplastic Agents, Phytogenic; Caspase 3; Caspase 7; Cell Cycle; Cell Survival; Chick Embryo; Chorioallantoic Membrane; Doxorubicin; Enzyme Activation; Flavones; Flavonoids; HeLa Cells; Hepatocytes; Humans; Inhibitory Concentration 50; Moraceae; Neovascularization, Pathologic; Oxazines; Plant Extracts; Quail; Structure-Activity Relationship; Time Factors; Xanthenes; Zygote