There are many biologically active chemicals which elicit an effect on the nervous system.

Researchers think that is because they contain different amounts of the active chemicals called ginsenosides.

The active chemical was chlorine added to the water as a disinfectant.

The plant was then given to an organic chemist who isolated the active chemical.

Marijuana or its active chemical, delta-9-tetrahydrocannabinol, is used to treat the nausea caused by some cancer therapies.

Some of the active chemicals it contains can pass into breast-milk.

Their screening produced two active chemicals, both belonging to the family known as polyphenols.

They usually come in small quantities and have low concentrations of the active chemicals.

These are cleaning products with active chemicals which remove the graffiti from the surface.

The active chemicals, the pyrethrins, are toxic to insect nervous systems.