Luteolin is a naturally occurring flavone that reportedly has anti-inflammatory effects. Because most luteolin is conjugated following intestinal absorption, free luteolin is likely present at low levels in the body. Therefore, luteolin metabolites are presumably responsible for luteolin bioactivity. Here we confirmed that luteolin glucuronides, especially luteolin-3'-O-glucuronide, are the major metabolites found in plasma after oral administration of luteolin (aglycone) or luteolin glucoside (luteolin-7-O-glucoside) to rats. Luteolin-4'-O-glucuronide and luteolin-7-O-glucuronide were also detectable together with luteolin-3'-O-glucuronide in the liver, kidney, and small intestine. Next, we prepared these luteolin glucuronides and compared the anti-inflammatory effects of luteolin and luteolin glucuronides on gene expression in lipopolysaccharide-treated RAW264.7 cells. Luteolin glucuronides, especially luteolin-7-O-glucuronide, reduced expression of inflammatory genes in the cells, although their effects were weaker than those of luteolin. These results indicate that the active compound responsible for the anti-inflammatory effect of luteolin in vivo would be luteolin glucuronide and/or residual luteolin.

No abstract

Sonochemiluminescence (SCL) of luminol due to a single bubble is studied through spectral measurement. No SCL was observed from a stable single bubble that emitted high-intensity sonoluminescence (SL). In contrast, SCL was observed under conditions of an unstable dancing bubble, where a bubble grows and ejects tiny bubbles, making it "dance" by counteraction. Furthermore, SCL was observed from dancing bubbles even when SL was not observed, depending on the dissolved gas content. The instability of bubble collapse is the key parameter governing SCL.

The orientation of fibers in a liquid irradiated with ultrasound is studied to realize the noncontact directional control of reinforcing fibers in the molten matrix of a composite material. The equations of translational and rotational motions of a fiber in a standing wave field are derived. The numerical solutions show the movement of the fibers at various initial positions and their stable positions and directions. Experiments are performed using polystyrene fibers of various lengths suspended in an aqueous sugar solution. Both numerical and experimental results indicate that polystyrene fibers shorter than one-fourth of the wavelength are constrained at the pressure node and are oriented in the direction perpendicular to that of wave propagation. On the other hand, fibers ranging from one-fourth to one-half of the wavelength have orientation either parallel to the direction of wave propagation at the pressure loop or perpendicular to that at the pressure node depending on their initial positions and directions.

Decrease in luminous intensity of multibubble sonoluminescence (MBSL) at excessive ultrasonic intensity is studied in connection with the behavior of cavitation bubbles. The intensity of MBSL from aerated distilled water in a rectangular vessel with six transducers, in which a standing wave field was established, was measured while the voltage applied to the transducers was increased. The corresponding change in the distribution of cavitation bubbles in the field was observed. The distributions of bubbles were compared with those of MBSL using an intesified charge-coupled device (ICCD) camera, and the bubble motion was observed with a high-speed camera. It is clarified that the expulsion of bubbles from the pressure antinode in the field is responsible for the decrease in MBSL intensity at high ultrasonic intensity. The expulsion is caused by the primary Bjerknes force which changes from an attractive force to a repulsive one depending on pressure amplitude and bubble radius, assisted by coalescence of bubbles due to the secondary Bjerknes force.