Ginkgoghrelins, unique acylated flavonoid diglycosides in Folium Ginkgo, stimulate growth hormone secretion via activation of the ghrelin receptor

Establishment of a Cell Line Stably Expressing the Growth Hormone Secretagogue Receptor to Identify Crocin as a Ghrelin Agonist

The growth hormone secretagogue receptor-1a (GHSR1a) is the endogenous receptor for ghrelin. Activation of GHSR1a participates in many physiological processes including energy homeostasis and eating behavior. Due to its transitory half-life, the efficacy of ghrelin treatment in patients is restricted; hence the development of new adjuvant therapy is an urgent need. This study aimed to establish a cell line stably expressing GHSR1a, which could be employed to screen potential ghrelin agonists from natural compounds. First, by means of lentiviral transduction, the genome of a human HEK293T cell was modified, and a cell platform stably overexpressing GHSR1a was successfully established. In this platform, GHSR1a was expressed as a fusion protein tagged with mCherry, which allowed the monitoring of the dynamic cellular distribution of GHSR1a by fluorescent microscopy. Subsequently, the authenticity of the GHSR1a mediated signaling was further characterized by using ghrelin and teaghrelin, two molecules known to stimulate GHSR1a. The results indicated that both ghrelin and teaghrelin readily activated GHSR1a mediated signaling pathways, presumably via increasing phosphorylation levels of ERK. The specific GHSR1a signaling was further validated by using SP-analog, an antagonist of GHSR1a as well as using a cell model with the knockdown expression of GHSR1a. Molecular modeling predicted that crocin might be a potential ghrelin agonist, and this prediction was further confirmed by the established platform.

Structure, synthesis, biosynthesis, and activity of the characteristic compounds from Ginkgo biloba L

Covering: 1928-2021Ginkgo biloba L. is one of the most distinctive plants to have emerged on earth and has no close living relatives. Owing to its phylogenetic divergence from other plants, G. biloba contains many compounds with unique structures that have served to broaden the chemical diversity of herbal medicine. Examples of such compounds include terpene trilactones (ginkgolides), acylated flavonol glycosides (ginkgoghrelins), biflavones (ginkgetin), ginkgotides and ginkgolic acids. The extract of G. biloba leaf is used to prevent and/or treat cardiovascular diseases, while many ginkgo-derived compounds are currently at various stages of preclinical and clinical trials worldwide. The global annual sales of G. biloba products are estimated to total US$10 billion. However, the content and purity of the active compounds isolated by traditional methods are usually low and subject to varying environmental factors, making it difficult to meet the huge demand of the international market. This highlights the need to develop new strategies for the preparation of these characteristic compounds from G. biloba. In this review, we provide a detailed description of the structures and bioactivities of these compounds and summarize the recent research on the development of strategies for the synthesis, biosynthesis, and biotechnological production of the characteristic terpenoids, flavonoids, and alkylphenols/alkylphenolic acids of G. biloba. Our aim is to provide an important point of reference for all scientists who research ginkgo-related compounds for medicinal or other purposes.

Anti-aging properties of phytoconstituents and phyto-nanoemulsions and their application in managing aging-related diseases

Aging is spontaneous and inevitable process in all living beings. It is a complex natural phenomenon that manifests as a gradual decline of physiological functions and homeostasis. Aging inevitably leads to age-associated injuries, diseases, and eventually death. The research on aging-associated diseases aimed at delaying, preventing or even reversing the aging process are of great significance for healthy aging and also for scientific progress. Numerous plant-derived compounds have anti-aging effects, but their therapeutic potential is limited due to their short shelf-life and low bioavailability. As the novel delivery system, nanoemulsion can effectively improve this defect. Nanoemulsions enhance the delivery of drugs to the target site, maintain the plasma concentration for a longer period, and minimize adverse reaction and side effects. This review describes the importance of nanoemulsions for the delivery of phyto-derived compounds and highlights the importance of nanoemulsions in the treatment of aging-related diseases. It also covers the methods of preparation, fate and safety of nanoemulsions, which will provide valuable information for the development of new strategies in treatment of aging-related diseases.

Anti-Inflammatory Principles from the Needles of Pinus taiwanensis Hayata and In Silico Studies of Their Potential Anti-Aging Effects

Pinus needle tea are very popular in Eastern countries such as Japan, Russia, Korea, and China. Pine needle tea is claimed to have significant anti-aging effects, but no clear evidence has supported this until now. In the present study, five undescribed compounds (1–5) as well as seventy-two known compounds were purified and characterized from the bioactive fraction of methanol extracts of P. taiwanensis needles. Most of the isolates were examined for their anti-inflammatory bioactivity by cellular neutrophil model and six compounds (45, 47, 48, 49, 50, and 51) exhibited a significant inhibition on superoxide anion generation and elastase release with IC₅₀ values ranging from 3.3 ± 0.9 to 8.3 ± 0.8 μM. These anti-inflammatory ingredients were subjected to docking computing to evaluate their binding affinity on the ghrelin receptor, which played an important role in regulating metabolism, with anti-aging effects. Compounds 49, 50, and 51 formed a stable complex with the ghrelin receptor via hydrogen bonds and different types of interactions. These results suggest the flavonoids are responsible for the potential anti-aging effects of pine needle tea.

Teaghrelin Protects SH-SY5Y Cells against MPP+-Induced Neurotoxicity through Activation of AMPK/SIRT1/PGC-1α and ERK1/2 Pathways

The prevalence and incidence of Parkinson’s disease (PD), an age-related neurodegenerative disease, are higher among elderly people. Independent of etiology, dysfunction and loss of dopaminergic neurons are common pathophysiological changes in PD patients with impaired motor and non-motor function. Currently, preventive or therapeutic treatment for combating PD is limited. The ghrelin axis and ghrelin receptor have been implicated in the preservation of dopaminergic neurons and have potential implications in PD treatment. Teaghrelin, a compound originating from Chin-Shin Oolong tea, exhibits ghrelin agonist activity. In this study, the neuroprotective potential of teaghrelin against PD was explored in a cell model in which human neuroblastoma SH-SY5Y cells were treated with the mitochondrial toxin 1-methyl-4-phenylpyridinium (MPP⁺). Upon MPP⁺ exposure, SH-SY5Y cells exhibited decreased mitochondrial complex I activity and apoptotic cell death. Teaghrelin activated AMP-activated protein kinase (AMPK)/sirtuin 1(SIRT1)/peroxisome proliferator-activated receptor gamma (PPARγ) coactivator-1α (PGC-1α) and extracellular signal–regulated kinases 1 and 2 (ERK1/2) pathways to antagonize MPP⁺-induced cell death. Herein, we propose that teaghrelin is a potential candidate for the therapeutic treatment of PD.

Quercetin 3-O-malonylglucoside in the leaves of mulberry (Morus alba) is a functional analog of ghrelin

Mulberry (Morus alba) leaf is traditionally consumed as a functional tea with remedial effects, such as preventing aging-related diseases. Two similar compounds, quercetin 3-O-malonylglucoside, and kaempferol 3-O-malonylglucoside, were detected in mulberry leaves and found to be structural recombinant composites of teaghrelin and emoghrelin, two classes of non-peptidyl compounds functionally identified as analogs of ghrelin. Molecular modeling showed that these two mulberry compounds were able to enter and interact with the ghrelin receptor and theoretical calculation revealed that they were similar to emoghrelin but slightly weaker than teaghrelin in terms of interaction with the receptor. The relatively abundant compound, quercetin 3-O-malonylglucoside was subjected to a bioactivity assay, and the result confirmed that it was able to increase the growth hormone secretion of rat anterior pituitary cells. It seems that quercetin 3-O-malonylglucoside is also a functional analog of ghrelin and presumably a key ingredient for the anti-aging activity of mulberry leaves. PRACTICAL APPLICATIONS: According to this study, quercetin 3-O-malonylglucoside and kaempferol 3-O-malonylglucoside are suggested to serve as active ingredients in tea products prepared from mulberry leaves. Contents of these two compounds might be used as key factors for breeding or screening mulberry varieties for commercial cultivation. Moreover, water extract of mulberry leaves containing these compounds can be used as an adequate supplement for functional food.

Development and validation of a sensitive LC-MS/MS method for the determination of 6-hydroxykynurenic acid in rat plasma and its application to pharmacokinetics study

A sensitive and specific bioanalytical method of liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the quantification of 6-hydroxykynurenic acid (6-HKA) in a small quantity of rat plasma has been developed and comprehensively validated. Tolbutamide (Tol) was used as the internal standard (IS). An aliquot of 50 μL rat plasma sample was deproteinized by 150 μL methanol, and then 100 μL of its supernatant was mixed with 100 μL water after centrifugation. Chromatographic separation was performed on a ZORBAX Eclipse Plus C₁₈ Rapid Resolution HD column (2.1 mm × 100 mm, 1.8 μm) with a gradient mobile phase consisting of water containing 2 mM ammonium formate and methanol at a flow rate of 0.2 mL/min over a total run time of 5.0 min. The mass spectrometer was operated under multiple reactions monitoring (MRM) mode with the transitions m/z 206.1 → 160.0 for 6-HKA and m/z 269.0 → 170.0 for Tol. The linear range was 2.5-250 ng/mL with the square regression coefficient (r²) of 0.997. The lower limit of quantification (LLOQ) was 2.5 ng/mL (Relative Error, RE +1.6% and RSD 4.8%, n = 5). The intra- and inter-day precision and accuracy was <13.3%. The mean recovery of 6-HKA in rat plasma was between the range of 99.3-103.4%. This method was successfully applied to study the pharmacokinetics of 6-HKA in rats after oral administration at a single dose of 20.0 mg/kg and after tail intravenous injection at a single dose of 2.0 mg/kg. Pharmacokinetic parameters bioavailability, C_{max, oral}, T_{max, oral}, AUC_{0-24h, oral}, AUC_{0-∞, oral}, AUC_{0-24h, iv} and AUC_{0-∞, iv} were 3.96%, 152.0 ± 85.5 ng/mL, 0.4 ± 0.1 h, 340.0 ± 136.3 ng/mL ∗ h, 369.5 ± 135.0 ng/mL ∗ h, 906.6 ± 324.1 ng/mL*h and 932.9 ± 336.5 ng/mL ∗ h, respectively.

Identification of two teaghrelins in Shy-jih-chuen oolong tea

Teaghrelins are unique acylated flavonoid tetraglycosides originally identified in Chin-shin oolong tea, and proposed to be potential oral analogs of ghrelin. Two acylated flavonoid tetraglycosides were isolated from Shy-jih-chuen oolong tea, and their chemical structures were determined to be quercetin and kaempferol 3-O-[α-L-arabinopyranosyl(1 → 3)][2"-O-(E)-p-coumaroyl] [β-D-glucopyranosyl(1 → 3)-α-L-rhamnopyranosyl(1 → 6)]-β-D-glucoside. These two compounds were extremely similar to the two teaghrelins (teaghrelin-1 and teaghrelin-2) in Chin-shin oolong tea by simply replacing a glucopyranosyl group with an arabinopyranosyl group. Molecular modeling showed that the two putative teaghrelins identified in Shy-jih-chuen docked to and interacted with the ghrelin receptor as well as teaghrelin-1 and teaghrelin-2. Mixture of these two putative teaghrelins was shown to enhance the release of growth hormone from primary anterior pituitary cells of rats. The results suggest that two teaghrelins, named teaghrelin-3 and teaghrelin-4, are present in Shy-jih-chuen oolong tea and possess biological activities analogous to teaghrelins in Chin-shin oolong tea. PRACTICAL APPLICATIONS: According to this study, teaghrelin-3 and teaghrelin-4 may be regarded as active ingredients for the quality control of Shy-jih-chuen oolong tea. The content of teaghrelins may serve as a key factor for the farmers to select new tea plants in their next propagation of Shy-jih-chuen cultivar. Crude water extract of Shy-jih-chuen oolong tea containing teaghrelins is considered to be an adequate food supplement or additive in functional food products.

Echinacoside Isolated from Cistanche tubulosa Putatively Stimulates Growth Hormone Secretion via Activation of the Ghrelin Receptor

Cistanche species, the ginseng of the desert, has been recorded to possess many biological activities in traditional Chinese pharmacopoeia and has been used as an anti-aging medicine. Three phenylethanoid glycosides—echinacoside, tubuloside A, and acteoside—were detected in the water extract of Cistanche tubulosa (Schenk) R. Wight and the major constituent, echinacoside, was further purified. Echinacoside of a concentration higher than 10⁻⁶ M displayed significant activity to stimulate growth hormone secretion of rat pituitary cells. Similar to growth hormone-releasing hormone-6, a synthetic analog of ghrelin, the stimulation of growth hormone secretion by echinacoside was inhibited by [D-Arg¹, D-Phe⁵, D-Trp^7,9, Leu¹¹]-substance P, an inverse agonist of the ghrelin receptor. Molecular modeling showed that all the three phenylethanoid glycosides adequately interacted with the binding pocket of the ghrelin receptor, and echinacoside displayed a slightly better interaction with the receptor than tubuloside A and acteoside. The results suggest that phenylethanoid glycosides, particularly echinacoside, are active constituents putatively responsible for the anti-aging effects of C. tubulosa and may be considered to develop as non-peptidyl analogues of ghrelin.

Important medicinal herbs in Parkinson's disease pharmacotherapy

Parkinson's disease (PD) is the most common progressive neurodegenerative movement disorder affecting more than 10 million people worldwide. The characteristic hallmark of PD involves progressive loss of dopaminergic (DA-ergic) neuron in Substantia Nigra pars compacta (SNpc) region of the brain, however, aetiology of the disease still remains unclear. Mitochondrial dysfunction and oxidative insult are considered to be the key culprit. The current therapy available for PD primarily relies on Levodopa that offers the potential of slowing down disease progression to some extent but includes lot of side effects. Any potential drug capable of treating or halting the disease still remains to be identified. It is evident that redox stabilization and replenishment of mitochondrial function seem to be an important therapeutic approach against PD as both are required for optimal neuronal functioning. Enormous research done in this field has shown that some natural and synthetic products exhibit neuroprotective and anti-apoptotic potential by improving mitochondrial function and alleviating oxidative stress. Therefore, the present review aims to discuss some of the important medicinal natural herbs (Bacopa monnieri, Mucuna pruriens, Withania somnifera, Curcuma longa, Gingko Biloba, and Camellia sinensis) in context to their neuroprotective potential and also in the development of novel therapeutic strategies against PD.