Rutin, luteolin, luteolin-7-glucoside, and chlorogenic acid gradually decomposed during heating at 100 °C. Even though they rapidly decomposed at 180 °C, some decomposition products still had radical-scavenging activity. When rutin was heated in the presence of chlorogenic acid, decomposition of rutin was almost totally inhibited at 100 °C, but was reduced at 180 °C. These results suggest that the radical-scavenging activity is more stable than the content of original polyphenolic compounds in foods during cooking and processing.

The stability and the coating characteristics of a variety of organozircon i u m c o m p o u n d s h a v e b e e n investigated to coat ZrO, films on stainless steel sheets for the improvement of heat resistance against oxidation. Zirconium tetraoctylate and zirconium tetrakis(acety1acetonate) were found to be more stable than zirconium alkoxides in an ambient atmosphere. The ZrO, films from zirconium alkoxides became white and discontinuous when the thicknes? of the films exceeded about 200 A (20 nm). On the other hand, transparent ZrO, films were obtained from zirconium tetraoctylate and zirconium tetrakis(acety1acetonate). The IR spectra of the films showed that the heat treatment at 400°C f o r 5 min produced organic-free ZrO, films. The heat resistance of stainless steel sheets against oxidation was improved by the ZrO, coating, depending on the film thickness. [

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The effects of ascorbic acid and ␣ ␣ ␣ ␣ ␣-tocopherol on the antioxidant activity of 15 phenolic compounds were compared with 2 in vitro assays. Combination of ascorbic acid or ␣ ␣ ␣ ␣ ␣-tocopherol plus polyphenolic compounds resulted in an additive effect as shown with DPPH-HPLC method. With the liposome oxidation method, combination of quercetin or catechins plus ␣ ␣ ␣ ␣ ␣-tocopherol showed synergistic effects.

Multidrug resistance (MDR) caused by the overexpression of ATPbinding cassette (ABC) transporters in cancer cells is a major obstacle in cancer chemotherapy. Previous studies have shown that curcumin, a natural product and a dietary constituent of turmeric, inhibits the function of MDR-related ABC transporters, including ABCB1, ABCC1, and especially ABCG2. However, the limited bioavailability of curcumin prevents its use for modulation of the function of these transporters in the clinical setting. In this study, we investigated the effects of 24 synthetic curcumin analogs with increased bioavailability on the transport function of ABCG2. The screening of the 24 synthetic analogs by means of flow cytometry revealed that four of the curcumin analogs (GO-Y030, GO-Y078, GO-Y168, and GO-Y172) significantly inhibited the efflux of the ABCG2 substrates, mitoxantrone and pheophorbide A, from ABCG2-overexpressing K562/breast cancer resistance protein (BCRP) cells. Biochemical analyses showed that GO-Y030, GO-Y078, and GO-Y172 stimulated the ATPase activity of ABCG2 at nanomolar concentrations and inhibited the photolabeling of ABCG2 with iodoarylazidoprazosin, suggesting that these analogs interact with the substrate-binding sites of ABCG2. In addition, when used in cytotoxicity assays, GO-Y030 and GO-Y078 were found to improve the sensitivity of the anticancer drug, SN-38, in K562/BCRP cells. Taken together, these results suggest that nontoxic synthetic curcumin analogs with increased bioavailability, especially GO-Y030 and GO-Y078, inhibit the function of ABCG2 by directly interacting at the substrate-binding site. These synthetic curcumin analogs could therefore be developed as potent modulators to overcome ABCG2-mediated MDR in cancer cells.