marmesin and imperatorin

Oxygraphic measurements of the rates of mitochondrial respiration in the presence of varying amounts of chalepin, imperatorin and marmesin, three naturally occurring furanocoumarins, revealed that the oxidation of NAD(+)-linked substrates was inhibited by chalepin and imperatorin and less significantly by marmesin. The order of potency being rotenone much greater than chalepin imperatorin greater than marmesin. There was no effect whatsoever on succinate oxidation by the furanocoumarins tested (up to 60 microM). State 3 respiration was also inhibited by these furanocoumarins; by at least 80% by 10 microM chalepin and by 48 and 29% with 60 microM imperatorin and 60 microM marmesin, respectively. Consequently, ADP control of respiration was diminished by those concentrations of furanocoumarins that inhibited respiration. At 60 microM, respiratory control ratio was reduced by about 88, 49 and 28% with chalepin, imperatorin and marmesin, respectively. A measurement of the rate of proton and Ca2(+)-movements across the mitochondrial coupling membrane demonstrated that succinate-supported transport was not affected by these furanocoumarins. On the other hand, pyruvate/malate-supported proton ejection was significantly inhibited by chalepin, imperatorin and marmesin. The order of the degree of inhibition of proton flux is rotenone much greater than chalepin greater than imperatorin greater than marmesin. The pattern of the inhibition of pyruvate/malate-supported Ca2(+)-transport was identical to that seen during proton transport. A comparison of the effects of chalepin to that of rotenone suggests that chalepin might be about 10 times less potent than rotenone.

Topics: Animals; Biological Transport; Calcium; Coumarins; Energy Metabolism; Furocoumarins; Mitochondria; NAD; Oxidation-Reduction; Oxygen; Protons; Rats; Rotenone; Succinates; Vitamin K

Topics: Coumarins; Furocoumarins; Medicine, Chinese Traditional; Medicine, East Asian Traditional; Plants, Medicinal; Sitosterols

Mutation by aflatoxin B1 (AFB1), imperatorin, marmesin, chalepin, and 8-methoxypsoralen (MOP), with and without black light (BL; long-wavelength ultraviolet light) activation, was determined at the hypoxanthine-guanine phosphoribosyltransferase locus (8-azaguanine resistance) in Chinese hamster V79 cells and at the ouabain locus in mouse C3H/1OT1/2 cells. Transformation by these furocoumarins under the same activation conditions was also investigated in C3H/1OT1/2 cells. In V79 cells, AFB1 induced a 4-fold maximum mutation frequency over controls under BL activation at a concentration of 5 micrograms/ml; marmesin induced a 2-fold increased mutation frequency at 1.5 micrograms/ml; MOP induced a 19-fold increase at 10 micrograms/ml; chalepin induced a 3-fold increase at 5 micrograms/ml; and imperatorin induced a 20-fold increase at 10 micrograms/ml. Essentially no mutation was observed at the ouabain-resistant (Ouar) locus in C3H/1OT1/2 cells with any of these compounds. In the transformation assays, type II and type III foci were observed at a 1-microgram/ml addition of AFB1 with or without BL activation; while with MOP and imperatorin, these types of foci were observed only with BL activation. Marmesin, although relatively more cytotoxic than the other furocoumarins studied, with a 50% lethal dose of less than 0.5 micrograms/ml, was not as mutagenic or potentially carcinogenic as were AFB1, imperatorin, or MOP with BL activation. These furocoumarins are considered to be involved in the etiology of the high incidence of skin cancer in Nigeria. Our experiments reinforce that concept and suggest that exposure to these furocoumarins may constitute a real carcinogenic hazard.

Topics: Aflatoxin B1; Aflatoxins; Animals; Cell Survival; Cell Transformation, Neoplastic; Coumarins; Cricetinae; Cricetulus; Fibroblasts; Furocoumarins; Lung; Methoxsalen; Mice; Mice, Inbred C3H; Nigeria; Plants, Medicinal