Efficient dehydration of 6-gingerol to 6-shogaol catalyzed by an acidic ionic liquid under ultrasound irradiation

Glycosylation of 6-gingerol and unusual spontaneous deglucosylation of two novel intermediates to form 6-shogaol-4'-O-β-glucoside by bacterial glycosyltransferase

6-Gingerol is a major phenolic compound within ginger (Zingiber officinale), often used in healthcare; however, its lower bioavailability is partly due to its poor solubility. Four bacterial glycosyltransferases (GTs) were tested to glycosylate 6-gingerol into soluble gingerol glucosides. BsUGT489 was a suitable GT to biotransform 6-gingerol into five significant products, which could be identified via nucleic magnetic resonance and mass spectrometry as 6-gingerol-4',5-O-β-diglucoside (1), 6-gingerol-4'-O-β-glucoside (2), 6-gingerol-5-O-β-glucoside (3), 6-shogaol-4'-O-β-glucoside (4), and 6-shogaol (5). The enzyme kinetics of BsUGT489 showed substrate inhibition toward 6-gingerol for producing two glucosides. The kinetic parameters were determined as KM (110 µM), kcat (862 min-1), and KI (571 µM) for the production of 6-gingerol-4'-O-β-glucoside (2) and KM (104 µM), kcat (889 min-1), and KI (545 µM) for the production of 6-gingerol-5-O-β-glucoside (3). The aqueous solubility of the three 6-gingerol glucosides, compound (1) to (3), was greatly improved. However, 6-shogaol-4'-O-β-glucoside (4) was found to be a product biotransformed from 6-shogaol (5). This study first confirmed that the glucose moiety at the C-5 position of both 6-gingerol-4',5-O-β-diglucoside (1) and 6-gingerol-5-O-β-glucoside (3) caused spontaneous deglucosylation through β-elimination to form 6-shogaol-4'-O-β-glucoside (4) and 6-shogaol (5), respectively. Moreover, the GTs could glycosylate 6-shogaol to form 6-shogaol-4'-O-β-glucoside (4). The assays showed 6-shogaol-4'-O-β-glucoside (4) had higher anti-inflammatory activity (IC50 value of 10.3 ± 0.2 µM) than 6-gingerol. The 6-gingerol-5-O-β-glucoside (3) possessed 346-fold higher solubility than 6-shogaol, in which the highly soluble glucoside is a potential prodrug of 6-shogaol via spontaneous deglucosylation. This unusual deglucosylation plays a vital role in influencing the anti-inflammatory activity.

IMPORTANCE

Both 6-gingerols and 6-shogaol possess multiple bioactivities. However, their poor solubility limits their application. The present study used bacterial GTs to catalyze the glycosylation of 6-gingerol, and the resulting gingerol glycosides were found to be new compounds with improved solubility and anti-inflammatory activity. In addition, two of the 6-gingerol glucosides were found to undergo spontaneous deglucosylation to form 6-shogaol or 6-shogaol glucosides. The unique spontaneous deglucosylation property of the new 6-gingerol glucosides makes them a good candidate for the prodrug of 6-shogaol.

An overview of 6-shogaol: new insights into its pharmacological properties and potential therapeutic activities

Ginger (Zingiber officinale Roscoe) has traditionally been used as a cooking spice and herbal medicine for treating nausea and vomiting. More recently, ginger was found to effectively reduce the risk of diseases such as gastroenteritis, migraine, gonarthritis, etc., due to its various bioactive compounds. 6-Shogaol, the pungent phenolic substance in ginger, is the most pharmacologically active among such compounds. The aim of the present study was to review the pharmacological characteristic of 6-shogaol, including the properties of anti-inflammatory, antioxidant and antitumour, and its corresponding molecular mechanism. With its multiple mechanisms, 6-shogaol is considered a beneficial natural compound, and therefore, this review will shed some light on the therapeutic role of 6-shogaol and provide a theoretical basis for the development and clinical application of 6-shogaol.

Unraveling the interconversion pharmacokinetics and oral bioavailability of the major ginger constituents: [6]-gingerol, [6]-shogaol, and zingerone after single-dose administration in rats

Background

The available in vitro evidences suggest the inherent instability and interconvertibility of [6]-gingerol and [6]-shogaol. However, limited data on their in vivo interconversion hinder understanding of their influence on the pharmacokinetic profiles.

Purpose

This study presents the first comprehensive in vivo investigation aiming to determine the interconversion pharmacokinetics in rats, and elucidate the oral bioavailability, target distribution, biotransformation, and excretion profiles of the key ginger constituents, [6]-gingerol, [6]-shogaol, and zingerone.

Methods

The pharmacokinetics was investigated through single intravenous (3 mg/kg) or oral (30 mg/kg) administration of [6]-gingerol, [6]-shogaol, or zingerone, followed by the determination of their tissue distribution after oral dosing (30 mg/kg). Intravenous pharmacokinetics was leveraged to evaluate the interconversion, circumventing potential confounders associated with the oral route.

Results

All rats tolerated these compounds throughout the pharmacokinetic study. The parent compounds exhibited rapid but partial absorption, and extensive organ distribution with substantial biotransformation, thereby limiting the oral bioavailability of each compound to below 2% when administered as pure compounds. Conversion of [6]-gingerol to [6]-shogaol after intravenous administration, demonstrated a significantly larger clearance compared to the reverse conversion ([6]-shogaol to [6]-gingerol). The irreversible metabolic clearance for both compounds was significantly greater than their reversible bioconversions. Furthermore, [6]-gingerol underwent biotransformation to zingerone. Conjugated glucuronides were eliminated partly through renal excretion, with minimal fecal excretion.

Conclusion

This in vivo investigation demonstrates the influence of interconversion on the disposition kinetics of [6]-gingerol, [6]-shogaol, and zingerone, as evidenced by the findings in the systemic circulation. The study further highlights the importance of considering this interconversion and tissue distribution when determining the administration dosage of ginger constituent combinations for therapeutic benefits and clinical applications.

Improving Ginger's Bioactive Composition by Combining Innovative Drying and Extraction Technologies

Ginger extracts (GEs) are antioxidant, antimicrobial, and anti-inflammatory. Their bioactivity can benefit foods and active packaging by extending shelf life, enhancing safety, and providing health benefits. Highly bioactive GEs are crucial to formulating potent active products and avoiding negative effects on their properties. Sesquiterpenes and phenolics are the main bioactives in ginger, but drying and extraction affect their composition. GEs are usually obtained from dry rhizomes; however, these operations have been studied independently. Therefore, a combined study of innovative drying and extraction technologies to evaluate their influence on extracts' composition will bring knowledge on how to increase the bioactivity of GEs. The effects of an emergent drying (vacuum microwave, VMD) followed by an emergent extraction (ultrasound, UAE, 20 or 80 °C) were investigated in this work. Microwave extraction (MAE) of fresh ginger was also studied. Convective oven drying and Soxhlet extraction were the references. Drying kinetics, powder color, extract composition, and antioxidant activity were studied. While MAE preserved the original composition profile, VMD combined with UAE (20 °C) produced extracts richer in phenolics (387.6 mg.GAE/g) and antioxidant activity (2100.7 mmol.Trolox/mL), with low impact in the sesquiterpenes. VMD generated shogaols by its high temperatures and facilitated extracting bioactives by destroying cellular structures and forming pores. UAE extracted these compounds selectively, released them from cell structures, and avoided losses caused by volatilization and thermal degradation. These findings have significant implications, as they provide an opportunity to obtain GE with tailored compositions that can enhance the formulation of food, active packaging, and pharmacological products.

Anticancer perspective of 6-shogaol: anticancer properties, mechanism of action, synergism and delivery system

Cancer is a malignant disease that has plagued human beings all the time, but the treatment effect of commonly used anticancer drugs in clinical practice is not ideal by reason of their drug tolerance and Strong adverse reactions to patients. Therefore, it is imperative to find effective and low-toxic anticancer drugs. Many research works have shown that natural products in Chinese herbal medicine have great anticancer potential, such as 6-shogaol, a monomer composition obtained from Chinese herbal ginger, which has been confirmed by numerous in vitro or vivo studies to be an excellent anti-cancer active substance. In addition, most notably, 6-shogaol has different selectivity for normal and cancer cells during treatment, which makes it valuable for further research and clinical development. Therefore, this review focus on the anti-cancer attributes, the mechanism and the regulation of related signaling pathways of 6-shogaol. In addition, its synergy with commonly used anticancer drugs, potential drug delivery systems and prospects for future research are discussed. This is the first review to comprehensively summarize the anti-cancer mechanism of 6-shogaol, hoping to provide a theoretical basis and guiding significance for future anti-cancer research and clinical development of 6-shogaol.

Cyclodextrin inclusion complex of a multi-component natural product by hot-melt extrusion

This study aimed to investigate whether hot-melt extrusion (HME) processing can promote molecular encapsulation of a multi-component natural product composed of volatile and pungent hydrophobic substances (ginger oleoresin (OR)) with cyclodextrins. 6-Gingerol and 6-shogaol, the biomarkers of ginger OR, were quantified by HPLC. Phase-solubility studies were performed using β-cyclodextrin (βCD) and hydroxypropyl-β-cyclodextrin (HPβCD) for ginger OR complexation. Solid complexes were then prepared by thermal (HME)- and solvent (slurry (SL))-based methods. Morphology, thermal behavior, solubility, in vitro dissolution, and in vivo anti-inflammatory activity were evaluated. HPβCD gave rise to AL-type complexes with ginger OR, whereas βCD led to materials with limited solubility. Ginger OR was complexed with HPβCD by HME without significant change in gingerol and shogaol content. Additionally, thermogravimetric analysis (TGA) suggested higher volatile retention in HME complexes than in SL ones. Shogaol and gingerol solubility and dissolution significantly increased from SL and HME complexes compared with ginger OR. In turn, 1:2 OR/HPβCD HME complex showed higher 6-shogaol solubility than SL, associated with a gradual release. The carrageenan-induced pleurisy test showed that the anti-inflammatory activity of ginger OR was maintained after complexation with HPβCD. The complexes significantly decrease the levels of IL-1β and inhibit cell migration. HME complex showed performance equivalent to the positive control and superior to the SL material. Taken together, these results indicate that HME can be useful for promoting the molecular encapsulation of complex natural products that contain volatile and thermolabile substances. HME complexes showed better in vivo and in vitro performance than complexes prepared using the solvent-based method.

Bioactivities and green advanced extraction technologies of ginger oleoresin extracts: A review

Zingiber officinale Roscoe is an excellent source of bioactive compounds, mainly gingerols and shogaols compounds, that associated with various bioactivities including antioxidant, anticancer, anti-inflammatory, antimicrobial, and antibiofilm. Zingiber officinale Roscoe found its application in the food, pharmaceutical, and cosmeceutical industries. The demand for a high quality of ginger oleoresin extracts based on the contents of gingerols and shogaols compounds for a health-benefit has dramatically increased. Various extraction techniques, including the conventional and advanced extraction techniques for gingerols and shogaols have been reported based on the literature data from 2012 to 2022. The present review examines the functional composition and bioactivities of Zingiber officinale Roscoe and the advanced green extraction technologies. Some variations in the quantity and quality of gingerols and shogaols compounds are because of the extraction method employed. This review provides a depth discussion of the various green advanced extraction technologies and the influences of process variables on the performance of the extraction process. Lower temperature with a short exposure time such as ultrasound-assisted and enzyme-assisted extraction, will lead to high quality of extracts with high content of 6-gingerol. High thermal processing, such as microwave-assisted and pressurized liquid extraction, will produce higher 6-shogaol. Meanwhile, supercritical fluid extraction promotes high quality and the safety of extracts by using non-toxic CO2. In addition, challenges and future prospects of the extraction of ginger oleoresin have been identified and discussed. The emerging green extraction methods and technologies show promising results with less energy input and higher quality extracts than conventional extraction methods.

Impact of drying and extractions processes on the recovery of gingerols and shogaols, the main bioactive compounds of ginger

Ginger extracts have anti-inflammatory, antioxidant, antitumor, and antibacterial activities mainly due to gingerols and shogaols. Extract composition and functionality can be affected by drying and extraction processes. Alternative methods to obtain ginger extracts based on high contents of gingerols and shogaols have been reported. However, there were no studies that present a broad overview of how these methods affect the composition and functionalities of ginger extracts. Based on literature data from 2011 to 2022, this review shows how drying, extraction, and complementary processes (i.e., enzymatic, acidic, and carbonic maceration) affect the composition and bioactivity of the ginger extract. Lower temperature processes, including freeze-drying, cold ultrasound-, or enzyme-assisted extraction, lead to extracts richer in phenolics, gingerols, and antioxidant activity. On the other hand, acidic solvents or "hot" processes including microwave-drying, pressurized liquid, and microwave-assisted extraction can favor higher shogaols concentrations, which have higher antitumor, anti-inflammatory, and antimicrobial activities than the gingerols precursors. Thus, in this review, we analyzed and discussed the relation between ginger processing and their bioactive compounds, focusing especially on gingerols and shogaols, as well as the main processes that increase the content of 6-shogaol without compromising other phenolic compounds to produce highly functional extracts for future applications in the food packaging sector.

A recent update on the multifaceted health benefits associated with ginger and its bioactive components

Due to recent lifestyle shifts and health discernments among consumers, synthetic drugs are facing the challenge of controlling disease development and progression. Various medicinal plants and their constituents are recognized for their imminent role in disease management via modulation of biological activities. At present, research scholars have diverted their attention on natural bioactive entities with health-boosting perception to combat the lifestyle-related disarrays. In particular, Zingiber officinale is a medicinal herb that has been commonly used in food and pharmaceutical products. Its detailed chemical composition and high value-added active components have been extensively studied. In this review, we have summarized the pharmacological potential of this well-endowed chemo preventive agent. It was revealed that its functionalities are attributed to several inherent chemical constituents, including 6-gingerol, 8-gingerol, 10-gingerol, 6-shogaol, 6-hydroshogaol, and oleoresin, which were established through many studies (in vitro, in vivo, and cell lines). In this review, we also focused on the therapeutic effects of ginger and its constituents for their effective antioxidant properties. Their consumption may reduce or delay the progression of related diseases, such as cancer, diabetes, and obesity, via modulation of genetic and metabolic activities. The updated data could elucidate the relationship of the extraction processes with the constituents and biological manifestations. We have collated the current knowledge (including the latest clinical data) about the bioactive compounds and bioactivities of ginger. Their detailed mechanisms, which can lay foundation for their food and medical applications are also discussed.

Dietary phytochemicals in the regulation of epithelial to mesenchymal transition and associated enzymes: A promising anticancer therapeutic approach

Epithelial to mesenchymal transition (EMT) is a biological phenomenon that plays a primordial role for initiation of metastasis. It renders cancer cells with increased self-renewal and tumor-initiating capabilities and exacerbated resistance to apoptosis and chemotherapy. Hence, regulation of EMT stands out to be an important strategy in controlling the behavior of malignant cells. Despite the enormous amount of preclinical data on the implication of EMT in cancer progression, there is still lack of routine clinical translation at therapeutic levels. The need of EMT-modulating drugs with high efficacy and low cytotoxicity has led to studies involving the evaluation of the efficacy of a plethora of various classes of phytochemicals present in dietary sources of fruits and vegetables. This review summarizes the role of these different classes of phytochemicals, their natural/synthetic analogs, and their nano-formulations in regulation of EMT in various preclinical models through attenuation of primary signaling pathways. Numerous proteins, transcription factors and enzymes targeted by various classes of phytochemicals in repression of EMT has been presented in this review. Additionally, we have critically analyzed the existing literature and provided views on new direction for accelerating the discovery of novel drug candidates which could be cautiously administered without concomitant effects.

[6]-Gingerol-induced cell cycle arrest, reactive oxygen species generation, and disruption of mitochondrial membrane potential are associated with apoptosis in human gastric cancer (AGS) cells

Ginger (Zingiber officinale Roscoe), a monocotyledonous herb, is widely used as an herbal medicine owing to the phytoconstituents it possesses. In the current study, the quantity of [6]-gingerol, the major phenolic ketone, in the fresh ginger and dried ginger rhizome was found to be 6.11 µg/mg and 0.407 µg/mg. Furthermore, [6]-gingerol was assessed for its antiapoptotic effects in human gastric adenocarcinoma (AGS) cells evidenced by acridine orange/ethidium bromide staining technique and Annexin-V assay. An increase in reactive oxygen species (ROS) generation led to a decrease in mitochondrial membrane potential (MMP) and subsequent induction of apoptosis. Results disclose that perturbations in MMP are associated with deregulation of Bax/Bcl-2 ratio at protein level, which leads to upregulation of cytochrome-c triggering the caspase cascade. These enduringly suggest that [6]-gingerol can be effectively used for targeting the mitochondrial energy metabolism to manage gastric cancer cells.

Occurrence, biological activity and metabolism of 6-shogaol

As one of the main bioactive compounds of dried ginger, 6-shogaol has been widely used to alleviate many ailments. It is also a major pungent flavor component, and its precursor prior to dehydration is 6-gingerol, which is reported to be responsible for the pungent flavor and biological activity of fresh ginger. Structurally, gingerols including 6-gingerol have a β-hydroxyl ketone moiety and is liable to dehydrate to generate an α,β-unsaturated ketone under heat and/or acidic conditions. The conjugation of the α,β-unsaturated ketone skeleton in the chemical structure of 6-shogaol explicates its higher potency and efficacy than 6-gingerol in terms of antioxidant, anti-inflammatory, anticancer, antiemetic and other bioactivities. Research on the health benefits of 6-shogaol has been conducted and results have been reported recently; however, scientific data are scattered due to a lack of systematic collection. In addition, action mechanisms of the preventive and/or therapeutic actions of 6-shogaol remain obscurely non-collective. Herein, we review the preparations, biological activity and mechanisms, and metabolism of 6-shogaol as well as the properties of 6-shogaol metabolites.