Mutations of Arginine 222 in Pre-transmembrane Domain I of Mouse 5-HT3A Receptor Abolish 20(R)- But Not 20(S)-Ginsenoside Rg3 Inhibition of 5-HT-Mediated Ion Currents

Rare ginsenosides: A unique perspective of ginseng research

BACKGROUND

Rare ginsenosides (Rg3, Rh2, C-K, etc.) refer to a group of dammarane triterpenoids that exist in low natural abundance, mostly produced by deglycosylation or side chain modification via physicochemical processing or metabolic transformation in gut, and last but not least, exhibited potent biological activity comparing to the primary ginsenosides, which lead to a high concern in both the research and development of ginseng and ginsenoside-related nutraceutical and natural products. Nevertheless, a comprehensive review on these promising compounds is not available yet.

AIM OF REVIEW

In this review, recent advances of Rare ginsenosides (RGs) were summarized dealing with the structurally diverse characteristics, traditional usage, drug discovery situation, clinical application, pharmacological effects and the underlying mechanisms, structure-activity relationship, toxicity, the stereochemistry properties, and production strategies.

KEY SCIENTIFIC CONCEPTS OF REVIEW

A total of 144 RGs with diverse skeletons and bioactivities were isolated from Panax species. RGs acted as natural ligands on some specific receptors, such as bile acid receptors, steroid hormone receptors, and adenosine diphosphate (ADP) receptors. The RGs showed promising bioactivities including immunoregulatory and adaptogen-like effect, anti-aging effect, anti-tumor effect, as well as their effects on cardiovascular and cerebrovascular system, central nervous system, obesity and diabetes, and interaction with gut microbiota. Clinical trials indicated the potential of RGs, while high quality data remains inadequate, and no obvious side effects was found. The stereochemistry properties induced by deglycosylation at C (20) were also addressed including pharmacodynamics behaviors, together with the state-of-art analytical strategies for the identification of saponin stereoisomers. Finally, the batch preparation of targeted RGs by designated strategies including heating or acid/ alkaline-assisted processes, and enzymatic biotransformation and biosynthesis were discussed. Hopefully, the present review can provide more clues for the extensive understanding and future in-depth research and development of RGs, originated from the worldwide well recognized ginseng plants.

Panax notoginseng saponins and their applications in nervous system disorders: a narrative review

Panax notoginseng saponins (PNS), also called "sanqi" in Chinese, are the main active ingredients which are extracted from the root of Panax notoginseng (Burk.) F. H. Chen., and they have been traditionally used as a medicine in China for hundreds of years with magical medicinal value. PNS have varied biological functions, such as anti-inflammatory effects, anti-cancer effects, anti-neurotoxicity, and the prevention of diabetes. Nervous system disorders, a spectrum of diseases originating from the nervous system, have a significant impact on all aspects of patients' lives. Due to the dramatic gains in global life expectancy, the prevalence of nervous system disorders is growing gradually. Even if the mechanism of these diseases is still not clear, they are mainly characterized by neuronal dysfunction and neuronal death. Consequently, it is essential to find measures to slow down or prevent the onset of these diseases. At present, traditional Chinese medicines, as well as their active components, have gained widespread popularity in preventing and treating these diseases because of their merits, especially PNS. In this review, we predominantly address the recent advances in PNS researches and their biological functions, and highlight their applications in nervous system disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), and stroke.

Stereoisomers of Saponins in Panax notoginseng (Sanqi): A Review

Panax notoginseng (Sanqi), a traditional Chinese medical drug which has been applied to medical use for over four centuries, contains high content of dammarane-type tetracyclic triterpenoid saponins. A number of stereoisomeric dammarane-type saponins exist in this precious herb, and some are particularly regarded as “biomarkers” in processed notoginseng. Contemporary researches have indicated that some saponin stereoisomers may show stereospecific pharmacological activities, such as anti-tumor, antioxidative, anti-photoaging, anti-inflammatory, antidiabetic, and neuro-protective activities, as well as stereoselective effects on ion channel current regulation, cardiovascular system, and immune system. The current review provides a comprehensive overview of chemical compositions of raw and processed P. notoginseng with a particular emphasis on saponin stereoisomers. Besides, the pharmacological and pharmacokinetic researches, as well as determination and biotechnological preparation methods of stereoisomeric saponins in notoginseng are discussed extensively.

Ginsenosides and their CNS targets

Ginsenosides are a special group of triterpenoid saponins attributed to medical effects of ginseng. Therefore, they have been research targets over the last three decades to explain ginseng actions and a wealth of literature has been presented reporting on ginsenosides' effects on the human body. Recently, there is increasing evidence on beneficial effects of ginsenosides to the central nervous system (CNS). Using a wide range of in vitro and in vivo models, researchers have attributed these effects to specific pharmacological actions of ginsenosides on cerebral metabolism, oxidative stress and radical formation, neurotransmitter imbalance and membrane stabilizing effects, and even antiapoptotic effects. Modulating these particular mechanisms by ginsenosides has thus been reported to exert either general stimulatory effects on the brain functions or protecting the CNS against various disease conditions. In this review, we try to address the recently reported ginsenosides' actions on different CNS targets particularly those supporting possible therapeutic efficacies in CNS disorders and neurodegenerative diseases.

Mutations Leu427, Asn428, and Leu431 residues within transmembrane domain-I-segment 6 attenuate ginsenoside-mediated L-type Ca(2+) channel current inhibitions

Many lines of evidences have shown that Panax ginseng exhibits beneficial effects on cardiovascular systems. We previously demonstrated that ginsenoside Rg(3) (Rg(3)), one of active ingredients of Panax ginseng, inhibits Ca(2+) channel currents in a stereospecific manner and affects the steady-state activation but not inactivation. This points a possibility that Rg(3) regulates Ca(2+) channels through specific interaction site(s) for Ca(2+) influx inhibition through Ca(2+) channels. However, it was not known how Rg(3) interacts with Ca(2+) channel proteins. In the current study, we sought to identify these site(s) in Xenopus oocytes expressing cardiac wild-type and mutant L(alpha(1C))-type Ca(2+) channels using the two-microelectrode voltage-clamp technique. To this end, we assessed how various point mutations of the L-type Ca(2+) channel affected the Rg(3) action. Mutations of L427R, N428R and L431K in transmembrane domain-I-segment 6 (IS6) of the channel significantly attenuated the Rg(3) action and caused rightward shifts in dose-response curves. Rg(3) treatment produced a negative shift in the inactivation voltage but did not alter the steady-state activation voltage, and none of the mutant channels affected the Rg(3)-induced negative shift of inactivation voltage. Rg(3) had no effects on inactivation time constant in wild-type and mutant channels. These results indicate that Rg(3) inhibition of L-type Ca(2+) channel currents is attenuated by mutations of Leu427, Asn428 and Leu431 in transmembrane IS6 residues. Leu427, Asn428 and Leu431 residues of the L-type Ca(2+) channel play important roles in the Rg(3) effect on channel properties.

Ginsenosides: are any of them candidates for drugs acting on the central nervous system?

The last two decades have shown a marked expansion in the number of publications regarding the effects of Panax ginseng. Ginsenosides, which are unique saponins isolated from Panax ginseng, are the pharmacologically active ingredients in ginseng, responsible for its effects on the central nervous system (CNS) and the peripheral nervous system. Recent studies have shown that ginsenosides regulate various types of ion channels, such as voltage-dependent and ligand-gated ion channels, in neuronal and heterologously expressed cells. Ginsenosides inhibit voltage-dependent Ca(2+), K(+), and Na(+) channel activities in a stereospecific manner. Ginsenosides also inhibit ligand-gated ion channels such as N-methyl-d-aspartate, some subtypes of nicotinic acetylcholine, and 5-hydroxytryptamine type 3 receptors. Competition and site-directed mutagenesis experiments revealed that ginsenosides interact with ligand-binding sites or channel pore sites and inhibit open states of ion channels. This review will introduce recent findings and advances on ginsenoside-induced regulation of ion channel activities in the CNS, and will further expand the possibilities that ginsenosides may be useful and potentially therapeutic choices in the treatment of neurodegenerative disorders.