Using human erythrocyte membranes (EMs) as a model system, we have examined photo-induced lipid peroxidation by a bis-methanophosphonate fullerene (BMPF) and four other fullerene derivatives including a mono-methanophosphonic acid fullerene (MMPF), a dimalonic acid C60 (DMA C60), a trimalonic acid C60 (TMA C60) and a polyhydroxylated fullerene (fullerol). Lipid peroxidation was assessed as the malondialdehyde (MDA) level measured by the thiobarbituric acid assay. It was observed that BMPF increased the MDA level of EMs after irradiation in both time- and dose-dependent manners. The photo-induced activity became very significant (p < 0.01) under the conditions of either the concentration of 10 μM and irradiation time of 30 min or the concentration of μ5 M and irradiation time of 60 min. Involvement of reactive oxygen species (ROS) in the activity was also examined by specific inhibitors of singlet oxygen, superoxide anions and hydroxyl radicals, respectively. While all three kinds were found responsible for the activity, the former two might play more important roles than the last one. Furthermore, the activity of BMPF was the strongest among all tested fullerene derivatives. These results indicated BMPF was a potential photosensitizer that would find application in photodynamic therapy.

Enzyme inhibition by fullerene derivatives has attracted much attention. In this communication, effects of two water-solube fullerene derivatives, fullerol and trimalonic acid C60 (TMA C60) on polymerase chain reaction (PCR) were investigated by using PCR of β-actin cDNA derived from HeLa cells as an experimental model. Both fullerol and TMA C60 were found to inhibit PCR in a dose-dependent manner. PCR was ultimately inhibited while the concentrations of each compound were not less than 0.01mM. In contrast, mannitol exerted no effects on PCR while its concentration increased up to 2mM. Compensation experiments with Thermus aquaticus (Taq) DNA polymerase revealed that both fullerol andTMAC60 inhibited the enzymatic activity of Taq DNA polymerase, and the inhibitory potency of TMA C60 was slightly greater than that of fullerol. Our data provides some novel aspects on the enzyme inhibiting activities of fullerene derivatives.

The e

Photo-induced cytotoxicity of malonic acid [C60] fullerene derivatives and its mechanism X. L. Yang*, C. H. Fan, H. S. Zhu Research Center of Materials Science, Beijing Institute of Technology, PO Box 327, Beijing 100081, PR China Accepted 10 August 2001 The biological activities of fullerenes have attracted extensive attention in recent years. The aim of this paper is to study the relation of the photo-induced cytotoxicity of fullerene derivatives to their chemical structures as well as the possible cellular mechanism involved in the photocytotoxicity. Three C60 derivatives with two to four malonic acid groups (DMA C60, TMA C60 and QMA C60) were prepared and the cytotoxicity of these compounds against HeLa cells was determined by MTT. Cell cycle was measured by flow cytometry. The results showed that the cytotoxicity of the malonic acid C60 derivatives was irradiation-and dosedependent. The sequence of their photo-induced growth inhibition was DMA C60>TMA C60>QMA C60. Hydroxyl radical quencher mannitol (10mm) was not able to prevent cells from the damage induced by irradiated DMA C60. DMA C60,together with irradiation,was found to have an ability of inducing a decrease in the number of G1 cells from 63 to 42% and a rise in that of G2+M cells from 6 to 26%. These data indicated that the number of malonic acid molecules added to C60 played an important role in the phototoxicity and the blockage of cell cycle might be a mechanism of this activity.

Although the pharmacology and clinical application of water extracts of Ganoderma lucidum have been extensively documented, little is known regarding its alcohol extract. In the present study, the anti-tumor effect of an alcohol extract of Ganoderma lucidumwas investigated using MCF-7 cells. We found that the alcohol extract of Ganoderma lucidum inhibited cell proliferation in a dose-and time-dependent manner, which might be mediated through up-regulation of p21/Waf1 and down-regulation of cyclin D1. Furthermore, this compound can directly induce apoptosis in MCF-7 cells, which might be mediated through up-regulation of a pro-apoptotic Bax protein and not by the immune system. Our findings suggest that there are multiple mechanisms underlying the anti-tumor effects of Ganoderma lucidum.