Modifications of Aliphatic Side Chain of 20(S)-Ginsenoside Rg_3 Cause an Enhancement or Loss of Brain Na^+ Channel Current Inhibitions(Highlighted paper selected by Editor-in-chief,Pharmacology)

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A line of evidence has shown that ginsenoside Rg_3 (Rg_3) could be one of bioactive ligands in brain Na^+ channel regulations. Rg_3 exists as stereoisomer of 20(R)- or 20(S)-form. Rg_3 consists of three different parts; steroid-like backbone structure, carbohydrate portion, and aliphatic side chain [-CH_2CH_2CH=C(CH_3)_2], which is cou-pled to the carbon-20 of backbone structure. In the previous report, we demonstrated that 20(S)- but not 20(R)-Rg_3 and carbohydrate portion of Rg_3 play important roles in rat brain Na_v1.2 channel regulations. However, little is known about the role of aliphatic side chain coupled to the carbon-20 in brain Na^+ channel regulations. In the present study, we prepared Rg_3 derivatives by modifying the aliphatic side chain of Rg_3, remaining with backbone structure and carbohydrate portion intact, and examined the effects of Rg_3 derivatives on Na^+ channel activity. We found that reduction of double bond in aliphatic side chain of Rg_3 exhibited agonistic actions in Na^+ channel current inhibitions by shifting concentration-response curve to leftward by three-fold, whereas deletion, hydroxylation, or oxygenation of aliphatic side chain caused an attenuation or loss of Na^+ channel current inhibitions. These results provide evidences that the aliphatic side chain of Rg_3 is also involved in Na+ channel regulations and further show a possibility that the aliphatic side chain of Rg_3 could be the target of chemical modifications for abolishment or potentiation of Rg_3 actions in Na^+ channel regulations.
社団法人日本薬学会の論文
2008-03-01

Modifications of Aliphatic Side Chain of 20(S)-Ginsenoside Rg_3 Cause an Enhancement or Loss of Brain Na^+ Channel Current Inhibitions(Highlighted paper selected by Editor-in-chief,Pharmacology)

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