Baicalein (5,6,7-trihydroxyflavone) is a flavone, a type of flavonoid, originally isolated from the roots of ''

Scutellaria baicalensis ''Scutellaria baicalensis'', with the common name Baikal skullcap or Chinese skullcap, is a species of flowering plant in the family Lamiaceae. Distribution The plant is native to China, Korea, Mongolia, and Russia in the Russian Far East and Si ...

'' and '' Scutellaria lateriflora''. It is also reported in '' Oroxylum indicum'' (Indian trumpetflower) and ''

Thyme Thyme () is the herb (dried aerial parts) of some members of the genus '' Thymus'' of aromatic perennial evergreen herbs in the mint family Lamiaceae. Thymes are relatives of the oregano genus ''Origanum'', with both plants being mostly indigen ...

''. It is the

aglycone An aglycone (aglycon or genin) is the compound remaining after the glycosyl group on a glycoside is replaced by a hydrogen atom. For example, the aglycone of a cardiac glycoside would be a steroid molecule. Detection A way to identify aglycone ...

baicalin As baicalin is a flavone glycoside, it is a flavonoid. It is the glucuronide of baicalein. Natural occurrences Baicalin is found in several species in the genus ''Scutellaria'', including ''Scutellaria baicalensis'', and '' Scutellaria lateri ...

. Baicalein is one of the active ingredients of Sho-Saiko-To, which is a Chinese classic herbal formula, and listed in Japan as Kampo medicine. As a Chinese herbal supplement, it is believed to enhance liver health. Baicalein, along with its analogue baicalin, is a

positive allosteric modulator In pharmacology and biochemistry, allosteric modulators are a group of substances that bind to a receptor to change that receptor's response to stimulus. Some of them, like benzodiazepines, are drugs. The site that an allosteric modulator binds to ...

of the

benzodiazepine site The GABAA receptor (GABAAR) is an ionotropic receptor and ligand-gated ion channel. Its endogenous ligand is γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system. Upon opening, the GABAA receptor o ...

and/or a non-benzodiazepine site of the GABA_A receptor. It displays subtype selectivity for α₂ and α₃ subunit-containing GABA_A receptors. In accordance, baicalein shows

anxiolytic An anxiolytic (; also antipanic or antianxiety agent) is a medication or other intervention that reduces anxiety. This effect is in contrast to anxiogenic agents which increase anxiety. Anxiolytic medications are used for the treatment of anxiet ...

effects in mice without incidence of sedation or myorelaxation. It is thought that baicalein, along with other flavonoids, may underlie the anxiolytic effects of ''S. baicalensis'' and ''S. lateriflora''. Baicalein is also an antagonist of the

estrogen receptor Estrogen receptors (ERs) are a group of proteins found inside cells. They are receptors that are activated by the hormone estrogen (17β-estradiol). Two classes of ER exist: nuclear estrogen receptors ( ERα and ERβ), which are members of the ...

, or an

antiestrogen Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or ...

. The flavonoid has been shown to inhibit certain types of

lipoxygenase Lipoxygenases () are a family of (non-heme) iron-containing enzymes most of which catalyze the dioxygenation of polyunsaturated fatty acids in lipids containing a cis,cis-1,4- pentadiene into cell signaling agents that serve diverse roles as aut ...

s and act as an

anti-inflammatory Anti-inflammatory is the property of a substance or treatment that reduces inflammation or swelling. Anti-inflammatory drugs, also called anti-inflammatories, make up about half of analgesics. These drugs remedy pain by reducing inflammation as o ...

agent. It has antiproliferative effects on ET-1-induced proliferation of pulmonary artery smooth muscle cell proliferation via inhibition of TRPC1 channel expression. Possible antidepressant effects have also been attributed to baicalein in animal research. Baicalein is an inhibitor of

CYP2C9 Cytochrome P450 family 2 subfamily C member 9 (abbreviated CYP2C9) is an enzyme protein. The enzyme is involved in metabolism, by oxidation, of both xenobiotics, including drugs, and endogenous compounds, including fatty acids. In humans, the prote ...

, an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

of the

cytochrome P450 Cytochromes P450 (CYPs) are a superfamily of enzymes containing heme as a cofactor that functions as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various co ...

system that

metabolizes Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...

drugs in the body. A derivative of baicalin is a known

prolyl endopeptidase Prolyl endopeptidase (PE) also known as prolyl oligopeptidase or post-proline cleaving enzyme is an enzyme that in humans is encoded by the ''PREP'' gene. Function Prolyl endopeptidase is a large cytosolic enzyme that belongs to a distinct cla ...

inhibitor. Baicalein has been shown to inhibit '' Staphylococcus aureus'' biofilm formation and the quorum sensing system in vitro. It has also been shown to be effective ''

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology ...

'' against all forms of ''

Borrelia burgdorferi ''Borrelia burgdorferi'' is a bacterial species of the spirochete class in the genus '' Borrelia'', and is one of the causative agents of Lyme disease in humans. Along with a few similar genospecies, some of which also cause Lyme disease, it mak ...

'' and ''

Borrelia garinii ''Borrelia garinii'' is a spirochete A spirochaete () or spirochete is a member of the phylum Spirochaetota (), (synonym Spirochaetes) which contains distinctive diderm (double-membrane) gram-negative bacteria, most of which have long, ...

''.

Glycosides

Tetuin is the 6- glucoside of baicalein.

References

{{Leukotrienergics Aromatase inhibitors Flavones Pyrogallols GABAA receptor positive allosteric modulators Antiestrogens Anxiolytics

Glycosides

See also

References