In this study from 2001, researchers tested the Hawaiian cultivars Mahakea, Nene, Moi, and non-native ISA for binding affinities to central nervous system receptors. For the purpose of this fact, we’ll be focusing on the root portion of this study. This study also includes results from leaf extractions which are outside of our normal kava drinking experience. The leaves were shown to contain DHK and DHM making up 70% of the kavalactone content, indicating if they were used for consumption, they would provide quite an unpleasant experience.
This study shows differing binding ability between cultivars for different receptors in vitro (in the lab/test tube) by using the measure IC50 or “Half maximal inhibitory concentration”. IC50 is defined as the measure of potency of a chemical in inhibiting a specific biological or biochemical function. It indicates how much of a particular chemical (drug) is needed to inhibit, in vitro, a process by 50%. In this paper they studied how well individual kavalactones prevented specific drugs from binding to their target receptor. It’s important to keep in mind that adding any chemical in sufficient quantities in vitro can cause binding affinities to show values higher than we would see in the real world.
In table two attached we are shown IC50 values of different root extracts and their corresponding affinity to bind at different receptor cites. Lower values indicate a greater ability to bind. Values indicated with “>1000” show no binding inhibition. Most of these values are so high we could essentially say these kavalactones exert very little effect, however it is interesting to see the higher affinity in the GABAa region. Further studies indicate kava does not bind to traditional GABAa sites seen in classical anxiolytics.
While we can’t exactly draw any specific conclusions of effects based on this study, it does lend evidence to the thought that different kava cultivars can affect our systems differently based on the kavalactone profile of the plant, and possibly other constituents that have yet to be named.
(Fun fact about this study, is that the researchers used LSD to study the binding affinity of kavalactones to serotonin)
Ic50. (2021, January 08). Retrieved March 29, 2021, from https://en.wikipedia.org/wiki/IC50
Dinh LD, Simmen U, Bueter KB, Bueter B, Lundstrom K, Schaffner W. Interaction of various Piper methysticum cultivars with CNS receptors in vitro. Planta Med. 2001 Jun;67(4):306-11. doi: 10.1055/s-2001-14334. PMID: 11458444.
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