Reversible Control of Third-Order Optical Nonlinearity of DNA Decorated Carbon Nanotube Hybrids.

Positive and negative third-order optical nonlinearities have been investigated in single-stranded DNA wrapped semiconducting single-walled carbon nanotubes. It is found that the redox reactions of hydrogen peroxide can reverse the sign of the third-order nonlinearity. The observation proves that the lowest unoccupied molecular orbital has a lower density of electronic states than that of the highest occupied molecular orbital. A three-energy-level model is used to explain the effect of the redox reactions. Raman spectroscopy has also been used to investigate the interaction between single-walled carbon nanotubes and single-stranded DNA.

Analysis of flavonoid phytoestrogens in botanical and ephedra-containing dietary supplements.

BACKGROUND: Plant-derived botanical and dietary supplements are widely self-prescribed in the US and considered natural, safe, and beneficial. However, because they are not strictly regulated by the Food and Drug Administration (FDA), their ingredients are not always known and they may contain unexpected agents. Among the myriad plant-produced molecules are flavonoids, which reportedly have various human health effects, including anticancer, antioxidant, and estrogenic properties. Several flavonoids (eg, isoflavones) are known as phytoestrogens, based on their ability to mimic estrogen in mammals. Because botanical and dietary supplements are plant products and need not be processed or purified due to their FDA classification as foods, they may contain unexpected phytoestrogens, such as flavonoids. OBJECTIVE: To analyze 8 botanical and 11 ephedra-containing dietary supplements for the presence and concentration of 5 flavonoids (biochanin A, daidzein, formononetin, genistein, quercetin), which may deliver unexpected estrogenic activity. METHOD: Randomly selected tablets from single bottles of 19 botanical and dietary supplements purchased locally were pooled. Flavonoids were extracted into ethanolic solution and analyzed by high-performance liquid chromatography. RESULTS: Flavonoids were detected in all supplements tested, with the largest number (4) found in Kava Kava. Almost all supplements contained measurable amounts of genistein and/or daidzein, known estrogenic agents, at up to 22 mg/day of isoflavone, per recommended daily dosage of supplement. CONCLUSIONS: These results suggest that single-component botanical and multi-ingredient dietary supplements could contain unexpected estrogenic agents, which may impact the health of consumers.