Chemical Insights into Ginseng as a Resource for Natural Antioxidants

Ginseng pharmacology: a new paradigm based on gintonin-lysophosphatidic acid receptor interactions

Ginseng, the root of Panax ginseng, is used as a traditional medicine. Despite the long history of the use of ginseng, there is no specific scientific or clinical rationale for ginseng pharmacology besides its application as a general tonic. The ambiguous description of ginseng pharmacology might be due to the absence of a predominant active ingredient that represents ginseng pharmacology. Recent studies show that ginseng abundantly contains lysophosphatidic acids (LPAs), which are phospholipid-derived growth factor with diverse biological functions including those claimed to be exhibited by ginseng. LPAs in ginseng form a complex with ginseng proteins, which can bind and deliver LPA to its cognate receptors with a high affinity. As a first messenger, gintonin produces second messenger Ca²⁺ via G protein-coupled LPA receptors. Ca²⁺ is an intracellular mediator of gintonin and initiates a cascade of amplifications for further intercellular communications by activation of Ca²⁺-dependent kinases, receptors, gliotransmitter, and neurotransmitter release. Ginsenosides, which have been regarded as primary ingredients of ginseng, cannot elicit intracellular [Ca²⁺]_i transients, since they lack specific cell surface receptor. However, ginsenosides exhibit non-specific ion channel and receptor regulations. This is the key characteristic that distinguishes gintonin from ginsenosides. Although the current discourse on ginseng pharmacology is focused on ginsenosides, gintonin can definitely provide a mode of action for ginseng pharmacology that ginsenosides cannot. This review article introduces a novel concept of ginseng ligand-LPA receptor interaction and proposes to establish a paradigm that shifts the focus from ginsenosides to gintonin as a major ingredient representing ginseng pharmacology.

Radiobiological modifiers in clinical radiation oncology: current reality and future potential

Radiation therapy can successfully ablate tumors. However, the same ionization process that destroys a cancer can also permanently damage surrounding organs resulting in unwanted clinical morbidity. Therefore, modern radiation therapy attempts to minimize dose to normal tissue to prevent side effects. Still, as tumors and normal tissues intercalate, the risk of normal tissue injury often may prevent tumoricidal doses of radiation therapy to be delivered. This paper will review current outcomes and limitations of radiobiological modifiers that may selectively enhance the radiosensitivity of tumors as well as parallel techniques that may protect normal tissues from radiation injury. Future endeavors based in part upon newly elucidated genetic pathways will be highlighted.

Chemical synthesis of saponins

Saponins are a large family of amphiphilic glycosides of steroids and triterpenes found in plants and some marine organisms. By expressing a large diversity of structures on both sugar chains and aglycones, saponins exhibit a wide range of biological and pharmacological properties and serve as major active principles in folk medicines, especially in traditional Chinese medicines. Isolation of saponins from natural sources is usually a formidable task due to the microheterogeneity of saponins in Nature. Chemical synthesis can provide access to large amounts of natural saponins as well as congeners for understanding their structure-activity relationships and mechanisms of action. This article presents a comprehensive account on chemical synthesis of saponins. First highlighted are general considerations on saponin synthesis, including preparation of aglycones and carbohydrate building blocks, assembly strategies, and protecting-group strategies. Next described is the state of the art in the synthesis of each type of saponins, with an emphasis on those representative saponins having sophisticated structures and potent biological activities.

Ginsenoside Rb1 attenuates angiotensin II-induced abdominal aortic aneurysm through inactivation of the JNK and p38 signaling pathways

BACKGROUND

Abdominal aortic aneurysm (AAA), a life-threatening vascular disease, accounts for approximately 10% of the morbidity in people over 65 years old. No satisfactory approach is available to treat AAA. Ginsenosides Rb1 and Rg1 are primary ingredients of Panax notoginseng for the treatment of cardiovascular diseases, but their impact on AAA is unknown.

METHODS AND RESULTS

An AAA model was established using an Ang II infusion in ApoE(-/-) mice. After continuous stimulation of Ang II for 28 days, suprarenal aortic aneurysms developed in 77% mice and 12% mice died suddenly due to AAA rupture. Administration of ginsenoside Rb1 (20 mg/kg/day), but not ginsenoside Rg1, significantly reduced the incidence and mortality of AAA. Ginsenoside Rb1 treatment dramatically suppressed Ang II-induced diameter enlargement, extracellular matrix degradation, matrix metalloproteinase (MMP) production, inflammatory cell infiltration, and vascular smooth muscle cell (VSMC) dysfunction. Mechanistic studies indicated that the protective effects of ginsenoside Rb1 were associated with the inactivation of JNK and p38 MAPK signaling pathways. A specific activator of JNK and p38, anisomycin, nearly abolished ginsenoside Rb1-driven suppression of MMP secretion by VSMCs.

CONCLUSIONS

Ginsenoside Rb1, as a potential anti-AAA agent, suppressed AAA through inhibiting the JNK and p38 signaling pathways.

Biosynthesis and biotechnological production of ginsenosides

Medicinal plants are essential for improving human health, and around 75% of the population in developing countries relies mainly on herb-based medicines for health care. As the king of herb plants, ginseng has been used for nearly 5,000 years in the oriental and recently in western medicines. Among the compounds studied in ginseng plants, ginsenosides have been shown to have multiple medical effects such as anti-oxidative, anti-aging, anti-cancer, adaptogenic and other health-improving activities. Ginsenosides belong to a group of triterpene saponins (also called ginseng saponins) that are found almost exclusively in Panax species and accumulated especially in the plant roots. In this review, we update the conserved and diversified pathway/enzyme biosynthesizing ginsenosides which have been presented. Particularly, we highlight recent milestone works on functional characterization of key genes dedicated to the production of ginsenosides, and their application in engineering plants and yeast cells for large-scale production of ginsenosides.

Enzymatic transformation of vina-ginsenoside R₇ to rare notoginsenoside ST-4 using a new recombinant glycoside hydrolase from Herpetosiphon aurantiacus

An eco-friendly and convenient preparation method for notoginsenoside ST-4 has been established by completely transforming vina-ginsenoside R7 using a recombinant glycosidase hydrolyzing enzyme (HaGH03) from Herpetosiphon aurantiacus. This enzyme specifically hydrolyzed the glucose at the C-20 position but not the external xylose or two inner glucoses at position C-3. Protein sequence BLAST revealed that HaGH03, composed of 749 amino acids and presumptively listed as a member of the family 3 glycoside hydrolases, has highest identity (48 %) identity with a thermostable β-glucosidase B, which was not known of any functions for ginsenoside transformation. The steady state kinetic parameters for purified HaGH03 measured against p-nitrophenyl β-D-glucopyranoside and vina-ginsenoside R7 were K M = 5.67 ± 0.24 μM and 0.59 ± 0.23 mM, and k cat = 69.2 ± 0.31/s and 2.15 ± 0.46/min, respectively. HaGH03 converted 2.5 mg/mL of vina-ginsenoside R7 to ST-4 with a molar yield of 100 % and a space-time yield of 104 mg/L/h in optimized conditions. These results underscore that HaGH03 has much potential for the effective preparation of target ginsenosides possessing valuable pharmacological activities. This is the first report identifying an enzyme that has the ability to transform vina-ginsenoside R7 and provides an approach to preparing rare notoginsenoside ST-4.

Antimelanogenic effect of ginsenoside Rg3 through extracellular signal-regulated kinase-mediated inhibition of microphthalmia-associated transcription factor

Background

Panax ginseng has been used to prolong longevity and is believed to be useful for improving skin complexion. Ginsenosides are the most active components isolated from ginseng, and ginsenoside Rg3 (G-Rg3) in particular has been demonstrated to possess antioxidative, antitumorigenic, and anti-inflammatory properties. The aim of this study was to examine the ability of G-Rg3 to inhibit melanogenesis.

Methods

The effects of G-Rg3 on melanin contents and the protein levels of tyrosinase, microphthalmia-associated transcription factor (MITF), and tyrosinase-related protein 1 (TRP1) were evaluated. Melanogenesis-regulating signaling molecules such as Akt and extracellular signal-regulated kinase (ERK) were also examined to explore G-Rg3-induced antimelanogenic mechanisms.

Results

G-Rg3 was found to significantly inhibit the synthesis of melanin in normal human epidermal melanocytes and B16F10 cells in a dose-dependent manner. The activity of cellular tyrosinase and the expression of MITF, tyrosinase, and TRP1 were all reduced, whereas ERK was strongly activated. PD98059 (a specific inhibitor of ERK) attenuated the G-Rg3-induced inhibition of melanin synthesis and tyrosinase activity.

Conclusion

Taken together, these results showed that G-Rg3 induces the activation of ERK, which accounts for its antimelanogenic effects. G-Rg3 may be a promising safe skin-whitening agent, adding to the long list of uses of P. ginseng for the enhancement of skin beauty.

Tissue-specific distribution of ginsenosides in different aged ginseng and antioxidant activity of ginseng leaf

The aim of this study was to systematically evaluate the effect of the cultivation year on the quality of different ginseng tissues. Qualitative and quantitative analyses of ginsenosides were conducted using a UPLC-UV-MS method. Eight main ginsenosides in three tissues (leaf, rhizome and main root) and four parts (periderm, phloem, cambium and xylem) of ginseng aged from 1 to 13 years were determined using a UPLC-PDA method. Additionally, the antioxidant capacities of ginseng leaves were analyzed by the DPPH, ABTS and HRSA methods. It was found that the contents of ginsenosides increased with cultivation years, causing a sequential content change of ginsenosides in an organ-specific manner: leaf > rhizome > main root. The ratio between protopanaxatriol (PPT, Rg₁, Re and RF) and protopanaxadiol (PPD, Rb₁, Rb₂, RC and Rd) in the main root remained stable (about 1.0), while it increased in leaf from 1.37 to 3.14 and decreased in the rhizome from 0.99 to 0.72. The amount of ginsenosides accumulated in the periderm was 45.48 mg/g, which was more than twice as high compared with the other three parts. Furthermore, the antioxidant activities of ginseng leaves were measured as Trolox equivalents, showing that antioxidant activity increased along with time of cultivation. The results show that the best harvest time for shizhu ginseng is the fifth year of cultivation, and the root and rhizome could be used together within seven planting years for their similar PPT/PPD level. Besides, the quality of the ginseng products would be enhanced with the periderm. The ginseng leaf is rich in ginsenosides and has potential application for its antioxidant capacity.

Comparative study on intestinal metabolism and absorption in vivo of ginsenosides in sulphur-fumigated and non-fumigated ginseng by ultra performance liquid chromatography quadruple time-of-flight mass spectrometry based chemical profiling approach

Our previous study indicated that sulphur-fumigation of ginseng in post-harvest handling processes could induce chemical transformation of ginsenosides to generate multiple ginsenoside sulphur derivatives. In this study, the influence of sulphur-fumigation on intestinal metabolism and absorption in vivo of ginsenosides in ginseng was sequentially studied. The intestinal metabolic and absorbed profiles of ginsenosides in rats after intra-gastric (i.g.) administration of sulphur-fumigated ginseng (SFG) and non-fumigated ginseng (NFG) were comparatively characterized by a newly established ultra performance liquid chromatography quadruple time-of-flight mass spectrometry (UPLC-QTOF-MS/MS) with electrospray ionization negative (ESI-) mode. A novel strategy based on the characteristic product ions and fragmentation pathways of different types of aglycones (saponin skeletons) and glycosyl moieties was proposed and successfully applied to rapid structural identification of ginsenoside sulphur derivatives and relevant metabolites. In total, 18 ginsenoside sulphur derivatives and 26 ginsenoside sulphur derivative metabolites in the faeces together with six ginsenoside sulphur derivatives in the plasma were identified in the SFG-administrated group but not in the NFG-administrated group. The results clearly demonstrated that the intestinal metabolic and absorbed profiles of ginsenosides in sulphur-fumigated and non-fumigated ginseng were quite different, which inspired that sulphur-fumigation of ginseng should not be recommended before the bioactivity and toxicity of the ginsenoside sulphur derivatives were systematically evaluated.

Ginsenoside Rb1 improves energy metabolism in the skeletal muscle of an animal model of postoperative fatigue syndrome

BACKGROUND

Postoperative fatigue syndrome (POFS) is a common clinical complication followed by almost every major abdominal surgery. Ginsenoside Rb1 (GRb1), a principle ginsenoside in ginseng, could exert a potent anti-fatigue effect on POFS. However, the mechanism is still unknown. Previous studies revealed that alterations in the energy metabolism in the skeletal muscle may play a vital role in the development and progression of fatigue. In the present study, we investigate the effect of GRb1 on energy metabolism in the skeletal muscle of a rat model of POFS induced by major small intestinal resection.

METHODS

GRb1 (10 mg/kg) was intraperitoneally administrated once daily for 1, 3, 7, and 10 d from the operation day, respectively. The locomotor activity was recorded every day, and total food intake was calculated starting from 24 h after surgery. After GRb1 treatment was completed, blood and skeletal muscle were sampled. The level of blood glucose was determined by an automatic biochemical analyzer. The content of adenosine triphosphate (ATP) in skeletal muscle was determined by high-performance liquid chromatography. The activity of energy metabolic enzymes Na(+)-K(+)-ATPase, pyruvate kinase, and succinate dehydrogenase (SDH) was assessed by commercially available kits.

RESULTS

The results revealed that GRb1 could increase locomotor activity of POFS rats and significantly increase their total food intake postoperatively (P < 0.05). Furthermore, GRb1 also significantly increased ATP content in the skeletal muscle of POFS rats (P < 0.05). Meanwhile, the activity of Na(+)-K(+)-ATPase and SDH in the skeletal muscle of POFS rats was enhanced by GRb1 (P < 0.05). However, no significant differences in blood glucose and pyruvate kinase were found between the POFS and GRb1 treatment rats (P > 0.05).

CONCLUSIONS

These results suggest that GRb1 may improve skeletal muscle energy metabolism in POFS, and the underlying mechanism may be associated with an increase in the content of ATP and an enhancement in the activity of energy metabolic enzymes such as Na(+)-K(+)-ATPase ATPase and SDH in the skeletal muscle.

Anti-fatigue effects of proteins isolated from Panax quinquefolium

ETHNOPHARMACOLOGICAL RELEVANCE

American ginseng (Panax quinquefolium) is an obligate shade perennial plant that belongs to Araliaceae ginseng species, and is native to eastern USA and Canada. Ginseng proteins are reported to have several pharmaceutical properties. However, such properties of American ginseng proteins (AGP) have seldom been reported. Also, anti-fatigue properties of AGP have not been studied. Therefore, we examined the anti-fatigue effects of AGP in mice.

MATERIALS AND METHODS

The molecular weight and protein contents of AGP were determined by SDS-PAGE, while the amino acid composition was analyzed by HPLC. The mice were divided into four groups. The control group was administered distilled water by gavage every day for 28 days. The other groups, designated as AGP treatment groups, were administered 125, 250 and 500 mg/kg of body weight, respectively of AGP by gavage every day for 28 days. Anti-fatigue activity was estimated using forced swimming test, and biochemical indices were determined using available kits.

RESULTS

The subunit molecular weight of AGP ranged from 8-66 kD and the protein content measured by Bradford assay was 1.86 mg/mL. The forced swimming time of low, intermediate and high groups were found to be longer as compared to the control group. AGP significantly decreased blood lactate (BLA) and serum urea nitrogen (SUN) levels, and increased hepatic glycogen (GLU) level. Additionally, AGP lowered malondialdehyde (MDA) content and increased the levels of glutathione peroxidase (GPx) and superoxide dismutase (SOD).

CONCLUSION

AGP shows anti-fatigue activity in mice, as measured by the physiological indices for fatigue.

Antidiabetic effects of malonyl ginsenosides from Panax ginseng on type 2 diabetic rats induced by high-fat diet and streptozotocin

ETHNOPHARMACOLOGY RELEVANCE

Ginseng (Panax ginseng C. A. Meyer) has been recorded to treat 'Xiao-ke' (emaciation and thirst) symptom in many ancient Chinese medical literatures (such as 'Shen Nong Ben Cao Jing') for thousands of years. 'Xiao-ke' symptom, in general, indicates diabetes mellitus.

AIM OF THE STUDY

Malonyl ginsenosides (MGR) are natural ginsenosides which exist in both fresh and air-dried ginseng. The objective of this study is to determine the antidiabetic function of MGR on type 2 diabetes.

MATERIALS AND METHODS

High fat diet-fed and streptozotocin-induced diabetic rats were treated with 50 and 100mg/kg/d of MGR or vehicle for 3 weeks. The effects of MGR on fasting blood glucose (FBG), intraperitoneal glucose tolerance test (IPGTT), serum insulin (SI), insulin tolerance test (ITT), body weight, total cholesterol (TC), and triglyceride (TG) levels in type 2 diabetic rats were measured.

RESULTS

After 3 weeks of treatment, MGR administration showed significantly lower FBG levels compared to the diabetic control group. In glucose tolerance test, IPGTT data showed that both MGR 50 and 100mg/kg groups significantly increased the glucose disposal after glucose load. The ITT also showed improvement of insulin sensitivity during 120 min of insulin treatment. In addition, MGR reduced TG and TC contents while showed no effect on body weight in diabetic rats.

CONCLUSION

The findings from this study suggest that MGR can alleviate hyperglycemia, hyperlipemia and insulin resistance of type 2 diabetes.