Kavalactone

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File:Kavalactone-general-numbered.svg
The general structure of the kavalactones, without the R1-R2 -O-CH2-O- bridge and with all possible C=C double bonds shown.

Kavalactones are a class of lactone compounds found in the kava shrub. Kavalactones have a wide variety of effects including amnestic, analgesic, anticonvulsant, anxiolytic, nootropic, and sedative/hypnotic activity caused by numerous interactions with the central nervous system via a myriad of mechanisms.

Enzyme inhibition

Kava extract has been shown to potently inhibit a wide range of hepatic enzymes, suggesting a very high potential for interactions with many pharmaceuticals and herbal medications.[1] For this reason, kava should never be consumed without the permission of a primary care physician, psychiatrist, and/or any other doctor who is prescribing medication for a patient. It is also recommended that potential users discuss their kava use with a pharmacist. If undergoing anesthesia, it is recommended to note any use of kava well in advance of any surgery. Patients may be instructed to temporarily discontinue use of kava for a set period of time before and after the surgery.

Toxicity

Several kavalactones (e.g.Methysticin and Yangonin) have been reported to be toxic and/or carcinogenic, although further research into these mechanisms is needed and it is not yet known if kava consumption induces toxic/carcinogenic effects in vivo. Despite this, hepatoxicity has been reported in a small portion of previously healthy kava users.[2][3]

Numerous kavalactones have apoptotic effects on various human tissues, which may be involved in some of the purported toxic effects of kava use.[4][5][6]

Compounds

See also: Flavokavain

At least 18 different kavalactones have been identified to date, with methysticin being the first identified.[7] Multiple analogues, such as ethysticin, have also been isolated.[8] Some consist of a substituted α-pyrone as the lactone while others are partially saturated.

Name Structure R1 R2 R3 R4
Yangonin 1 -OCH3 -H -H -H
10-methoxyyangonin 1 -OCH3 -H -OCH3 -H
11-methoxyyangonin 1 -OCH3 -OCH3 -H -H
11-hydroxyyangonin 1 -OCH3 -OH -H -H
Desmethoxyyangonin 1 -H -H -H -H
11-methoxy-12-hydroxydehydrokavain 1 -OH -OCH3 -H -H
7,8-dihydroyangonin 2 -OCH3 -H -H -H
Kavain 3 -H -H -H -H
5-hydroxykavain 3 -H -H -H -OH
5,6-dihydroyangonin 3 -OCH3 -H -H -H
7,8-dihydrokavain 4 -H -H -H -H
5,6,7,8-tetrahydroyangonin 4 -OCH3 -H -H -H
5,6-dehydromethysticin 5 -O-CH2-O- -H -H
Methysticin 7 -O-CH2-O- -H -H
7,8-dihydromethysticin 8 -O-CH2-O- -H -H
Kavalactones: General structures

See also

References

  1. James M. Mathews, Amy S. Etheridge and Sherry R. Black. "Inhibition of Human Cytochrome P450 Activities by Kava Extract and Kavalactones". 
  2. Dr Joji Malani (2002). "Evaluation of the effects of Kava on the Liver" (PDF). Retrieved 2008-01-05. 
  3. AC Brown (2007). "Traditional kava beverage consumption and liver function tests in a predominantly Tongan population in Hawaii revealed no liver impairment.". Retrieved 2009-03-17. 
  4. Tang, J; Dunlop, RA; Rowe, A; Rodgers, KJ; Ramzan, I (2010). "Kavalactones Yangonin and Methysticin Induce Apoptosis in Human Hepatocytes (HepG2) In Vitro.". Phytotherapy research : PTR 25 (3): n/a. PMID 20734326. doi:10.1002/ptr.3283. 
  5. Zi X, Simoneau AR (April 2005). "Flavokawain A, a novel chalcone from kava extract, induces apoptosis in bladder cancer cells by involvement of Bax protein-dependent and mitochondria-dependent apoptotic pathway and suppresses tumor growth in mice.". Cancer Research 65 (8): 3479–86. PMID 15833884. doi:10.1158/0008-5472.CAN-04-3803. 
  6. Ramez N. Eskander1, Leslie M. Randall1, Toshinori Sakai, Yi Guy, Bang Hoang, Xiaolin Zi. "Flavokawain B, a novel, naturally occurring chalcone, exhibits robust apoptotic effects and induces G2/M arrest of a uterine leiomyosarcoma cell line". 
  7. Naumov, P.; Dragull, K.; Yoshioka, M.; Tang, C.-S.; Ng, S. W. (2008). "Structural Characterization of Genuine (-)-Pipermethystine, (-)-Epoxypipermethystine, (+)-Dihydromethysticin and Yangonin from the Kava Plant (Piper methysticum)". Natural Product Communications 3 (8): 1333–1336. 
  8. Shulgin, A. (1973). "The narcotic pepper - the chemistry and pharmacology of Piper methysticum and related species". Bulletin on Narcotics (UNODC) (2): 59–74. 

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