L-trytophan is an essential amino acid (it must be supplied in the diet).  It is converted to serotonin, a neurotransmitter that helps to control mood by calming anxiety, relieving depression, and aiding sleep.  Most horse owners know about tryptophan due to its reputation  for being the culprit for sleepiness after eating turkey at Thanksgiving.  In reality, turkey has the same amount of tryptophan as other types of poultry.  Low doses have been shown to actually cause excitement in horses and extremely high oral does can product hemolysis (breakdown of red blood cells) due to conversion of tryptophan to indole (a hemolytic metabolite) in the digestive tract.

Valerian (valeriana officinalis) is a tall perennial hearb with white to pinkish purple flowers.  The root is used medicinally.  The name valerian comes from the Latin work vlare that means "well being."  Over 150 phytochemicals have been isolated from valerian root.  The ones that shown to have shown to have sedative effects on the central nervous system include:  valerenic acids, valepotriates, GABA, tyrosine, arginine, and glutamine.  The effects of valerian root in humans are somewhat dose dependent with lower does relieving anxiety and nervousness, and higher doses aiding sleep. 

Magnesium is a mineral that is essential for healthy function of almost all body systems.  In the body it is found as an ion within the cells.  Along with calcium, Magnesium helps to control muscle activity and nerve conduction. Calcium stimulates activity, whereas,  magnesium decreases or suppresses activity.  Magnesium has been found to decrease nerve exitation, decrease adrenaline secretion, decrease cortisol release, and to decrease muscle contraction by binding to intracellular ATP and breaking the actin-myosin bounds that cause muscles to contract.  In very high doses magnesium acts as a laxative and can cause muscle weakness.

B vitamins are essential for converting food to fuel.  They also help to stabilize lactate levels that can cause anxiety.  Likely B vitamins largest impact on calming is due to its use a co-factor in the production of serotonin and norepinephrine.

Kava Kava (piper methysticum) is a tall shrub with large heart shaped leaves and roots that look like bundles of woody, hairy branches.  The roots are ground up and used medicinally.  The teas has long been a traditional ceremonial drink in the Pacific Islands.  Kava kava contains kavlactones, specifically kavapyrones that reduce convulsions, promote sleep, and cause muscle relaxation.  The tea produces relaxation and a feeling of well being.  There have been cases of liver damage reported in humans.

Inositol is a carbohydrate (previously thought to be B-vitamin) that functions a signaling molecule.  It can modulate serotonin activity, thus producing a calming effect.

Red Raspberry Leaf (Rubus idaeus) is a source of magnesium and B vitamins.  Studies both in vitro and in vivo show that use of the leaves  either as a tea or an extract relaxes uterine muscles.  The active compounds have not been definitely identified.

Chamomile (matricaria chamomilla) is an herb with a small white daisy like flower with a yellow center that is a member of the aster family (which also includes ragweed).  The flower contains volatile oils that contina the active ingredients bisabolol, apigenin, iluteolin, and matricin.  Bisabolol has antispasmodic and anti-inflammatory properties.  The constituents responsible for the sedative properties of chamomile have not been identified.  The sedation is only mild.

Black Cohosh (actaea ra cemosa and cimicifuga racemosa) is a member of the buttercup family, a perennial plan that is native to North America.  The roots are used medicinally.  One active chemical is a saponin called 26-deoxyactein, but its mode of action is not known.  Black Cohosh is most often used for female reproductive issues.  A recently identified compound called fuinolic acid has some estrogenic activity.  There have been a few isolated cases of liver failure in humans taking Black Cohosh.

Passion Fruit (passiflora incarnate) is a perennial creeping vine native to the Southern U.S. and South America.  The whole of the above ground parts of the plant are dried and used to make tea.  The plant contains alkaloids, glyosides, and flavanoids that in combination product the plants sedative effect.  The plant also contain naturally occurring serotonin and maltol, which has sedative effects. 

Ginger (zingiber officinalis) is a herbaceous, perennial plant native to South Eastern Asia that is grown there, as well as extensively in Jamaica.  The rhizome is used medicinally.  Ginger contains oleoresins that are rich in gingerols.  These compounds have a variety of sedative effects.