Trivalent Gold

Trivalent gold is sigiuficantly more toxic to aquatic biota than monovalent gold. Gold, as tetrachloroaurate (AuCl ), depressed 

Growth inhibition of yeast (Saccharomyces cerevisiae) was observed in 40 h at the lowest concentration tested of 20.0 mg Au /L, with no growth observed at 50.0 mg/L. Both calcium and magnesium enhanced the inhibitory effect of gold on the yeast cells. 

Results of acute toxicity bioassays of 96-h duration with adults of Fundulus heteroclitus, an estuarine cyprinodontiform killihsh, and salts of various metals and metalloids showed that gold, as auric chloride (Au+ ), was comparatively lethal, with 50% dead in 96 h at 0.8 mg/L. The relative order of lethality, with silver (Ag), most toxic and lithium (Li) least toxic was Ag+, Hg+, Au+, Cd, followed by As+ Be, Al, Cu, Zn, Y, Tl, Fe, La, Cr+, Ni, Co, Sb, and Li. Salts of 13 additional elements tested to Fundulus were less toxic than were salts of Li, including Rb, Si, Mo, Re, Ba, Mn, Ca, Sr, K, and Na, in that order. 

When bullfrog skeletal muscle hbers previously pretreated with 98.5mg/kg Au+ (as gold sodium thiomalate) were subjected to 2.0 mg Au /kg as NaAuCL, the hbers lost their ability to contract upon electrical stim-ulahon, as was the case for 2.0 mg Au+ /kg alone. However in the presence of thiomalic acid, Au did not completely block tetanus tension, even at 10 mg Au+ /kg. Thiomalic acid also inhibited Au -induced membrane depolarization. In bullfrogs, skeletal muscle hbers spontaneously produced phasic and toihc contractures upon addihon of 5-20 xM Ag+ or more than 50 xM Au+ 9.0 mg 

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Berrodier, I., Farges, F., Benedetti, M., Winterer, M., Brown Jr, G. E., Deveughele, M. (2004). Adsorption mechanisms of trivalent gold on iron- and aluminum-(oxy)hydroxides. Part 1 X-ray absorption and Raman scattering spectroscopic studies of Au(III) adsorbed on ferrihydrite, goethite, and boehmite. Geochimica et Cosmochimica Acta, 68(14), 3019-3042. doi 10.1016/j.gca.2004.02.009... 

Cances, B., Benedetti, M., Farges, F., Brown, G. E. (2007). Adsorption mechanisms of trivalent gold onto iron Oxy-Hydroxides From the molecular scale to the model. InB. Hedman P. Painetta (Eds.), 13th International Conference on X-Ray Absorption Fine Structure (XAFS13) (Vol. 882, pp. 217-219). Stanford, CA, USA. 

The stabilities of the oxidation states within this series are disturbingly free from trends. For copper, the +2 state predominates for silver, the + 1 state is most important finally, of the known gold compounds for which a valence state of the metal may be easily assigned, most contain trivalent gold. At higher temperatures, the cuprous state of copper becomes more important than the cupric. 

A large number of coordination compounds of trivalent gold have been made, and organometaliic derivatives have also been studied. Certain compounds of both of these classes are interesting both structurally and chemically, but are best treated in a more specialized work. 

The baths contain both sulfite and thiosulfate with trivalent gold chloride. What is the form of gold complex that is actually reduced to gold metal ... 

When trivalent gold is mixed with sulfite and thiosulfate, it is reduced to monovalent gold. Kato et al. studied the stoichiometry of the redox reaction and arrived at the conclusion that the predominant gold species in the system is [Au(S203)2], a monovalent gold thiosulfate complex. If the solution contains only sulfite but no thiosulfate, the gold complex takes the form of [Au(S03)2] , a monovalent gold sulfite complex ... 

The steady state radiolysis of gold compounds is mainly concerned with the reduction of trivalent gold to the metal (13, 16). The reported yield, G(-Aum)eq = 2.3 0.2 (16), has been interpreted to arise from 2GH2o2 + Gh — G0h, where the G s stand for the primary radiolytic yields. From the point of view of pulse radiolytic investigation, Au1 is, however, more interesting. Since monovalent gold is unstable except when complexed (17), the choice of a suitable compound is very limited. 

The decay of this gold transient follows a second order law as one would expect from disproportionation of Au11, but its slope is only half of that in neutral solution. This indicates that the species which are formed in acid solutions are more stable than those in neutral solution, probably because of differences in the chloride complexes. In spite of these differences, the observed similarity of the spectra seem to indicate that the transitions responsible for the spectra are possibly the same, maybe from the ligand to the central metal atom, as has been suggested for the case of the chloride complex of the trivalent gold (25). 

In compound 2", the porphyrin incorporates a trivalent gold which was selected for two reasons (i) it forms very stable porphyrin complexes and will thus not be lost during the synthesis of the second porphyrin nucleus [13] and (ii) because of its strong electropositive character, it confers to the aromatic porphyrin ring to which it is complexed a remarkable electron-accepting abihty with a resulting very accessible reduction potential [41-44[. The reactions leading to the transition metal-complexed [2]- and [3[rotax-anes 8 and respectively, are indicated in Fig. 5 [45[. 

Anti-tumor properties of monovalent and trivalent gold complexes are documented. 

Au+ /L). Simultaneous application of 5 xM Ag+ and 20 (xM Au+ inhibited contractures induced by Ag+. Trivalent gold applied immediately after development of Ag+-induced contractures shortened the durahon of the phasic contracture and markedly decreased the tonic contracture through modihcahon of the Ca" " release chaimel. It was concluded that extracellular Au+ at cointara-hvely low concentrations inhibits the silver (Ag+)-induced contrachons in skeletal muscle and that intracellular Au+ achvates the sarcoplasmic reticulum Ca+ release channel to parhally contribute to the tonic contrachons. 

Trivalent gold complexes were potentially attractive as anticancer agents because of their cytotoxic effects on established human tumor cell lines. All tested Au+ complexes substantially retained their antitumor potency against platinum-resistant tumor cell lines for leukemia and ovarian cancer. Cytotoxicity of these compounds in vitro is attributed to binding with DNA and modification and subsequent impairment of replication and transcription processes. The paucity of data on Au+ complexes probably derives from their high redox potential and relatively poor stability, which makes their use problematical under physiological conditions. 

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