Ellagitannin and flavonoid constituents from Agrimonia pilosa Ledeb. with their protein tyrosine phosphatase and acetylcholinesterase inhibitory activities

Anti-Inflammatory Flavonoids from Agrimonia pilosa Ledeb: Focusing on Activity-Guided Isolation

To elucidate the anti-inflammatory properties and constituents of Agrimonia pilosa Ledeb. (A. pilosa), a comprehensive investigation was conducted employing activity-guided isolation. The anti-inflammatory effects were evaluated through an in vitro nitric oxide (NO) assay on lipopolysaccharide (LPS)-treated RAW 264.7 macrophage cells. Seven bio-active compounds with anti-inflammatory properties were successfully isolated from the butanol fraction and identified as follows: quercetin-7-O-β-d-rhamnoside (1), apigenin-7-O-β-d-glucopyranoside (2), kaempferol-7-O-β-d-glucopyranoside (3), quercetin (4), kaempferol (5), apigenin (6), and apigenin-7-O-β-d-glucuronide-6″-butylester (7). All isolated compounds showed strong NO inhibitory activity with IC50 values ranging from 1.4 to 31 µM. Compound 6 demonstrated the most potent NO inhibition. Compound 7, a rare flavonoid, was discerned as a novel anti-inflammatory agent, ascertained through its inaugural demonstration of nitric oxide inhibition. Subsequently, a comprehensive structure-activity relationship (SAR) analysis was conducted employing eight flavonoids derived from A. pilosa. The outcomes elucidated that flavones exhibit superior NO inhibitory effects compared to flavonols, and the aglycone form manifests greater potency in NO inhibition than the glycone counterpart. These results highlight A. pilosa as a promising source of effective anti-inflammatory agents and indicate its potential as a health-beneficial dietary supplement and therapeutic material.

Structural determination and anticholinesterase assay of C-glycosidic ellagitannins from Lawsonia inermis leaves: A study supported by DFT calculations and molecular docking

An ellagitannin monomer, lythracin M (1), and a dimer, lythracin D (2), along with eight known monomers (3-10) were isolated from Lawsonia inermis (Lythraceae) leaves. Lythracin M (1) is a C-glycosidic ellagitannin with a flavogallonyl dilactone moiety that participates in the creation of a γ-lactone ring with the anomeric carbon of the glucose core. Lythracin D (2) was determined as an atropisomer of the reported lythcarin D. These newly discovered structures (1 and 2) were determined by intensive spectroscopic experiments and by comparing DFT-calculated ¹H¹H coupling, ¹H NMR chemical shifts, and ECD data with experimental values. The anti-acetylcholinesterase assay of the compounds 1-10 revealed that the C-1 ellagitannin epimers [casuarinin (7; IC₅₀ = 34 ± 2 nM) and stachyurin (8; IC₅₀ = 56 ± 3 nM)], and the new dimer (2; IC₅₀ = 61 ± 4 nM) possess enzyme inhibitory effects comparable to the reference drug (donepezil, IC₅₀ = 44 ± 3 nM). Molecular docking of compounds 1-10 with AChE identified the free galloyl moiety as an important pharmacophore in the anticholinesterase activity of tannins.

Status of research on natural protein tyrosine phosphatase 1B inhibitors as potential antidiabetic agents: Update

Protein tyrosine phosphatase 1B (PTP1B) is a crucial therapeutic target for multiple human diseases comprising type 2 diabetes (T2DM) and obesity because it is a seminal part of a negative regulator in both insulin and leptin signaling pathways. PTP1B inhibitors increase insulin receptor sensitivity and have the ability to cure insulin resistance-related diseases. However, the few PTP1B inhibitors that entered the clinic (Ertiprotafib, ISIS-113715, Trodusquemine, and JTT-551) were discontinued due to side effects or low selectivity. Molecules with broad chemical diversity extracted from natural products have been reported to be potent PTP1B inhibitors with few side effects. This article summarizes the recent PTP1B inhibitors extracted from natural products, clarifying the current research progress, and providing new options for designing new and effective PTP1B inhibitors.

Systematic Identification of the Main Constituents from Agrimonia pilosa Ledeb. and Their Metabolites in Rats using HPLC-Q-TOF-MS/MS

Agrimonia pilosa is a perennial herbaceous flowering plant, commonly known as agrimony or hairy agrimony. The dried aerial parts of this species have been widely used for the treatment of acute diarrhea, hemostasis, and other inflammation-related diseases. However, information on the in vivo metabolism of A. pilosa constituents is limited. In this study, the phytochemical profile of A. pilosa was investigated using HPLC-Q-TOF-MS/MS combined with a nontargeted diagnostic ion network analysis strategy. An information-dependent acquisition method with multiple filters was utilized to screen possible prototypes and metabolites in complex biological matrices. Furthermore, various data-processing techniques were applied to analyze possible prototypes and their metabolites in rat plasma, feces, and urine following oral administration of A. pilosa extract. A total of 62 compounds, which belonged to five main structural classes (21 phenols, 22 flavonoids, 6 coumarins, 3 triterpenes, and 10 organic acids), were tentatively identified in A. pilosa. In addition, using our proposed stepwise method, 32 prototypes and 69 metabolites were detected in rat plasma, feces, and urine. The main metabolic pathways after the oral administration of A. pilosa extract were revealed to include methylation, dihydroxylation, demethylation, hydrolysis, sulfation, and glucuronidation. This comprehensive in vivo and in vitro identification of the possible active components in A. pilosa could provide a basis for understanding its various pharmacological activities.

Agrimonia Pilosa Ledeb.: A review of its traditional uses, botany, phytochemistry, pharmacology, and toxicology

Ethnopharmacological relevance

Agrimonia pilosa Ledeb. is the dried above-ground part of dragon's tooth grass, a plant of the Rosaceae family, which is widely distributed in China, Korea, and Japan. Agrimonia pilosa Ledeb. is a herbal medicine with great scope for development and use. It is astringent and hemostatic, and it is used for treating malaria, preventing dysentery, detoxification, and as a tonic for deficiency.

Aim of the review

We summarize the traditional uses, botanical and chemical composition, extraction methods, and pharmacological and toxicological progress of Agrimonia pilosa Ledeb. and discuss the future research trends and development prospects of this plant.

Materials and methods

Information on Agrimonia pilosa Ledeb. was gathered via the Internet (China National Knowledge Infrastructure, Google Scholar, PubMed, Web of Science, SpringerLink, Wiley, Wanfang Data, and Baidu Academic). Additional information was obtained from books (Ben Cao Tu Jing, A Textual Research on the Name and Reality of Plants, Modern Practical Chinese Medicine, Zhen Nan Ben Cao) and PhD and MS dissertations.

Results

Phytochemical studies have identified more than 252 compounds from Agrimonia pilosa Ledeb., including flavonoids, volatile oils, tannins, phenols, m-benzotrienols, pentacyclic triterpenoids, isocoumarins, lignans, organic acids, and other chemical constituents. The compounds and extracts isolated from Agrimonia pilosa Ledeb. show various pharmacological activities, including anti-inflammatory, anticancer, antitumor effects, antioxidant, analgesic effects, and other pharmacological effects.

Conclusion

This review highlights the botany, phytochemistry, pharmacology, toxicology, and traditional uses of Agrimonia pilosa Ledeb., providing a basis for future research and clinical applications. Agrimonia pilosa Ledeb. has shown remarkable effectiveness in the treatment of various diseases, especially enteritis, gastric ulcers, and gastrointestinal bleeding. Most prescriptions for Agrimonia pilosa Ledeb. are empirical and lack rigorous clinical observation. For these reasons, the toxicology, standardized clinical studies, nature of active ingredients, pharmacokinetics, mechanism, and metabolism of Agrimonia pilosa Ledeb. should be deepened, especially through clinical trials, to ensure the clinical safety of its use for further research.

Determination of Anti-Alzheimer's Disease Activity of Selected Plant Ingredients

Neurodegenerative diseases, among which one of the more common is Alzheimer’s disease, are the one of the biggest global public health challenges facing our generation because of the increasing elderly population in most countries. With the growing burden of these diseases, it is essential to discover and develop new treatment options capable of preventing and treating them. Neurodegenerative diseases, among which one of the most common is Alzheimer’s disease, are a multifactorial disease and therefore demand multiple therapeutic approaches. One of the most important therapeutic strategies is controlling the level of acetylcholine—a neurotransmitter in cholinergic synapses—by blocking the degradation of acetylcholine using acetylcholinesterase inhibitors such as tacrine, galantamine, donepezil and rivastigmine. However, these drugs can cause some adverse side effects, such as hepatotoxicity and gastrointestinal disorder. Thus, the search for new, more effective drugs is very important. In the last few years, different active constituents from plants have been tested as potential drugs in neurodegenerative disease therapy. The availability, lower price and less toxic effects of herbal medicines compared with synthetic agents make them a simple and excellent choice in the treatment of neurodegenerative diseases. The empirical approach to discovering new drugs from the systematic screening of plant extracts or plant-derived compounds is still an important strategy when it comes to finding new biologically active substances. The aim of this review is to identify new, safe and effective compounds that are potential candidates for further in vivo and clinical tests from which more effective drugs for the treatment of Alzheimer’s disease could be selected. We reviewed the methods used to determine anti-Alzheimer’s disease activity. Here, we have discussed the relevance of plant-derived compounds with in vitro activity. Various plants and phytochemical compounds have shown different activity that could be beneficial in the treatment of Alzheimer’s disorders. Most often, medicinal plants and their active components have been investigated as acetylcholinesterase and/or butyrylcholinesterase activity inhibitors, modifiers of β-amyloid processing and antioxidant agents. This study also aims to highlight species with assessed efficacy, usable plant parts and the most active plant components in order to identify species and compounds of interest for further study. Future research directions are suggested and recommendations made to expand the use of medicinal plants, their formulations and plant-derived active compounds to prevent, mitigate and treat Alzheimer’s disease.

Agrimonia pilosa: A Phytochemical and Pharmacological Review

Agrimonia pilosa Ledeb., which belongs to Agrimonia and Rosaceae, is used in traditional Chinese medicine. It exhibits excellent medicinal properties and has been used to treat various diseases, such as tumors, trichomoniasis, vaginitis, diarrhea, and dysentery. Phytochemical studies have revealed that Agrimonia has over 100 secondary metabolites that can be categorized into six classes, i.e., flavonoids, isocoumarins, triterpenes, phloroglucinol derivatives, tannins, and organic acids. This review summarizes recently published literature on the chemical structures of 90 bioactive compounds that have been identified in A. pilosa and examines their pharmacological properties, including their antitumor, anti-inflammatory, antioxidant, antibacterial, and antidiabetic properties, as well as the potential development of parasitic resistance to these chemicals. This review highlights existing knowledge gap and serves as a basis for developing novel preparations of A. pilosa with medicinal value.

Approaches to Decrease Hyperglycemia by Targeting Impaired Hepatic Glucose Homeostasis Using Medicinal Plants

Liver plays a pivotal role in maintaining blood glucose levels through complex processes which involve the disposal, storage, and endogenous production of this carbohydrate. Insulin is the hormone responsible for regulating hepatic glucose production and glucose storage as glycogen, thus abnormalities in its function lead to hyperglycemia in obese or diabetic patients because of higher production rates and lower capacity to store glucose. In this context, two different but complementary therapeutic approaches can be highlighted to avoid the hyperglycemia generated by the hepatic insulin resistance: 1) enhancing insulin function by inhibiting the protein tyrosine phosphatase 1B, one of the main enzymes that disrupt the insulin signal, and 2) direct regulation of key enzymes involved in hepatic glucose production and glycogen synthesis/breakdown. It is recognized that medicinal plants are a valuable source of molecules with special properties and a wide range of scaffolds that can improve hepatic glucose metabolism. Some molecules, especially phenolic compounds and terpenoids, exhibit a powerful inhibitory capacity on protein tyrosine phosphatase 1B and decrease the expression or activity of the key enzymes involved in the gluconeogenic pathway, such as phosphoenolpyruvate carboxykinase or glucose 6-phosphatase. This review shed light on the progress made in the past 7 years in medicinal plants capable of improving hepatic glucose homeostasis through the two proposed approaches. We suggest that Coreopsis tinctoria, Lithocarpus polystachyus, and Panax ginseng can be good candidates for developing herbal medicines or phytomedicines that target inhibition of hepatic glucose output as they can modulate the activity of PTP-1B, the expression of gluconeogenic enzymes, and the glycogen content.

The triterpenoids and sesquiterpenoids from the plant of Agrimonia pilosa

A phytochemistry of the whole plant of Agrimonia pilosa led to the discovery of two new nortriterpenoids, agrimonorterpenes A and B (1 and 2), together with one known triterpenoid fupenzic acid (3) and seven known sesquiterpenoids (4-10). The new structures were determined as 19α-hydroxy-2-oxo-nor-A (3)-urs-11,12-dien-28-oic acid (1) and 2, 19β-dihydroxy-3-oxo-23-noroleana-1, 4, 12-trien-28-oic acid (2) by the spectroscopic data of UV, IR, HR-ESI-MS, and NMR. Notably, the structure of 1 possessed a rare five-membered A ring. And this is the first time to discover the sesquiterpenoids (4-10) from A. pilosa. Compound 3 displayed the selective cytotoxicity against HCT116, BGC823, and HepG2 cell lines with the IC₅₀ values of 16.31 μM, 21.94 μM, and 23.40 μM, respectively.

Potent antiviral activity of Agrimonia pilosa, Galla rhois, and their components against SARS-CoV-2

Agrimonia pilosa (AP), Galla rhois (RG), and their mixture (APRG64) strongly inhibited SARS-CoV-2 by interfering with multiple steps of the viral life cycle including viral entry and replication. Furthermore, among 12 components identified in APRG64, three displayed strong antiviral activity, ursolic acid (1), quercetin (7), and 1,2,3,4,6-penta-O-galloyl-β-d-glucose (12). Molecular docking analysis showed these components to bind potently to the spike receptor-binding-domain (RBD) of the SARS-CoV-2 and its variant B.1.1.7. Taken together, these findings indicate APRG64 as a potent drug candidate to treat SARS-CoV-2 and its variants.

A comprehensive review on the antidiabetic activity of flavonoids targeting PTP1B and DPP-4: a structure-activity relationship analysis

Type 2 diabetes (T2D) is an expanding global health problem, resulting from defects in insulin secretion and/or insulin resistance. In the past few years, both protein tyrosine phosphatase 1B (PTP1B) and dipeptidyl peptidase-4 (DPP-4), as well as their role in T2D, have attracted the attention of the scientific community. PTP1B plays an important role in insulin resistance and is currently one of the most promising targets for the treatment of T2D, since no available PTP1B inhibitors were still approved. DPP-4 inhibitors are among the most recent agents used in the treatment of T2D (although its use has been associated with possible cardiovascular adverse events). The antidiabetic properties of flavonoids are well-recognized, and include inhibitory effects on the above enzymes, although hitherto not therapeutically explored. In the present study, a comprehensive review of the literature of both synthetic and natural isolated flavonoids as inhibitors of PTP1B and DPP-4 activities is made, including their type of inhibition and experimental conditions, and structure-activity relationship, covering a total of 351 compounds. We intend to provide the most favorable chemical features of flavonoids for the inhibition of PTP1B and DPP-4, gathering information for the future development of compounds with improved potential as T2D therapeutic agents.

The discovery of new phloroglucinol glycosides from Agrimonia pilosa and the mechanism of oxidative dearomatization of the methyl-substituted phloroglucinol derivatives

New phloroglucinol glycosides, aglycones, and oxidative dearomatized products of aglycones were discovered from Agrimonia pilosa, and the mechanism of the auto oxidative dearomatization was disclosed as a free radical chain reaction with ³O₂.

Cuphea calophylla var. mesostemon (Koehne) S.A. Graham: A Whole-Ethnopharmacological Investigation

Several species of Cuphea are used medicinally and are reported to have cardioprotective, diuretic, and antihypertensive properties. In Brazil, Cuphea species are collectively called "sete-sangrias" due to their similar appearances and are also used interchangeably for the same therapeutic purposes. So the aim of the study was to characterize morphoanatomy of leaves and stems, evaluate the safety, and investigate the diuretic, hypotensive, vasodilatory, and antioxidant properties of ethanol-soluble fraction of Cuphea calophylla var. mesostemon (Koehne) S.A. Graham. Initially, the morphoanatomical characterization of the leaves and stems of C. calophylla var. mesostemon was performed. For the pharmacological evaluation, the ethanol-soluble fraction from Cuphea calophylla (ESCC) was obtained and chemically characterized by high-performance liquid chromatography coupled with a diode array detector and tandem mass spectrometry techniques. Then, acute toxicity, diuretic, hypotensive, antioxidant, and vasodilatory effects were evaluated in Wistar rats. The main chemical compounds identified from ESCC were gallic acid derivatives, ellagitannins, and flavonoids. ESCC showed no acute toxic effect. ESCC showed no acute toxic effect and the estimated median lethal dose (LD₅₀) was above 2000 mg/kg. ESCC treatment (30, 100, and 300 mg/kg) did not present any significant acute diuretic or hypotensive effects. However, an important reduction in the elimination of electrolytes was observed after the acute administration, and a significant increase in renal sodium elimination was observed after 7 days of treatment. In the cardiac tissue, the groups treated with ESCC presented significant increase in superoxide dismutase activity.

Phenolome of Asian Agrimony Tea (Agrimonia asiatica Juz., Rosaceae): LC-MS Profile, α-Glucosidase Inhibitory Potential and Stability

Functional beverages constitute the rapidly increasing part of the functional food section and represent an area with a wide range of products including herbal-based beverages. We carried out screening investigations of the extracts of 85 Rosaceous tea plants. Among the extracts analyzed Agrimonia asiatica herb extract demonstrated the highest inhibitory activity against the enzyme α-glucosidase (20.29 µg/mL). As a result of chromato-mass-spectrometric profiling of A. asiatica herb with high-performance liquid chromatography with photodiode array and electrospray triple quadrupole mass-spectrometric detection (HPLC-PDA-ESI-tQ-MS) 60 compounds were identified, including catechins, ellagitannins, flavones, flavonols, gallotannins, hydroxycinnamates, procyanidins, most for the very first time. The analysis of the seasonal variation of metabolites in A. asiatica herb demonstrated that the phenolic content was highest in summer samples and lower in spring and autumn. HPLC activity-based profiling was utilized to identify compounds of A. asiatica herb with the maximal α-glucosidase inhibitory activity. The most pronounced inhibition of α-glucosidase was observed for agrimoniin, while less significant results of inhibition were revealed for ellagic acid and isoquercitrin. The evaluation of phenolic content in A. asiatica herbal teas with the subsequent determination of α-glucosidase inhibiting potential was discovered. Maximum inhibition of α-glucosidase was observed for hot infusion (75.33 µg/mL) and the minimum for 30 min decoction (159.14 µg/mL). Our study demonstrated that A. asiatica herbal tea is a prospective functional beverage in which dietary intake may help to reduce blood glucose.

Flavones as a Privileged Scaffold in Drug Discovery: Current Developments

BACKGROUND

Flavones are one of the main subclasses of flavonoids with diverse pharmacological properties. They have been reported to possess antimalarial, antimicrobial, anti-tuberculosis, anti-allergic, antioxidant, anti-inflammatory activities, among others.

OBJECTIVE

The present review summarizes the recent information on the pharmacological properties of naturally occurring and synthetic flavones.

METHODS

Scientific publications referring to natural and synthetic flavones in relation to their biological activities were hand-searched in databases such as SciFinder, PubMed (National Library of Medicine), Science Direct, Wiley, ACS, SciELO, Springer, among others.

RESULTS

As per the literature, seventy-five natural flavones were predicted as active compounds with reference to their IC50 (<20 µg/mL) in in vitro studies. Also, synthetic flavones were found active against several diseases.

CONCLUSION

As per the literature, flavones are important sources for the potential treatment of multifactorial diseases. However, efforts toward the development of flavone-based therapeutic agents are still needed. The appearance of new catalysts and chemical transformations is expected to provide avenues for the synthesis of unexplored flavones, leading to the discovery of flavones with new properties and biological activities.

Laxative Metabolites from the Leaves of Moringa oleifera

Three new flavonoids, quercetin-3-O-6-[methyl-(S)-3-hydroxy-3-methylglutaroyl(1→6]-β-d-glucopyranoside (1), kaempferol-3-O-[methyl-(S)-3-hydroxy-3-methylglutaroyl(1→6)]-β-d-glucopyranoside (2), and quercetin-3-O-6-[(E)-4-methoxy-5-methylhexa-2,4-dienoatyl(1→6)]-β-d-glucopyranoside (3), and two new alkaloids, 5-dehydroxymethyl-pyrrolemarumine 4″-O-α-l-rhamnopyranoside (4) and N¹-methyl-N²-((4-O-α-l-rhamnopyranoside)benzyl) oxalamide (5), together with 45 known compounds (6-50) were isolated from the leaves of Moringa oleifera Lam. Among those compounds, 1-octacosanol (50), a straight-chain 28-carbon alcohol, exhibited good activity against diphenoxylate-induced constipation in mice, which is obtained as a laxative constituent from the plant for the first time. In order to have an accurate understanding of the content of compound 50, a quantification with gas chromatography-tandem mass spectrometry (GC-MS/MS) was carried out. The anti-inflammatory and α-glucosidase inhibitory activity of some compounds also was assessed.

Secondary metabolites isolated from Agrimonia pilosa Ledeb

A pilot study on the ethanol extracts of Agrimonia pilosa found to have anti-α-glucosidase and anti-inflammatory activities. Subsequent chemical study afforded a new phenylethyl isocoumarin glycoside (1) and eight known compounds (2-9). The structure of 1 was elucidated by comprehensive spectroscopic analysis and chemical transformations. All compounds showed modest α-glucosidase inhibitory activity (IC₅₀ values ranging from 36.8 to 210.7 μM), which was lower than that of the positive control acarbose (IC₅₀=301.9 μM). Those compounds except inactive compounds 3 and 6 showed weak anti-inflammatory activity.[Formula: see text].

Recent Advances in the Production and Applications of Ellagic Acid and Its Derivatives. A Review

Ellagitannins (ETs), characterized by their diversity and chemical complexity, belong to the class of hydrolysable tannins that, via hydrolysis under acidic or alkaline conditions, can yield ellagic acid (EA). They are mostly found as a part of extractives in angiosperms. As known antioxidants and chelators, EA and EA derivatives are drawing an increasing interest towards extensive technical and biomedical applications. The latter ones include possible antibacterial, antifungal, antiviral, anti-inflammatory, hepato- and cardioprotective, chemopreventive, neuroprotective, anti-diabetic, gastroprotective, antihyperlipidemic, and antidepressant-like activities, among others. EA’s synthesis and production challenges prompt further research on new methods and alternative sources. Conventional and prospective methods and raw materials for the production of EA and its derivatives are reviewed. Among the potential sources of EA, the residues and industrial streams of the pulp industry have been highlighted and considered as an alluring alternative in terms of commercial exploitation.

Evaluation of genetic toxicity, acute and sub-chronic oral toxicity and systemic safety of Agrimonia pilosa and Rhus gall 50% ethanolic extract mixture (APRG64) in vitro and in vivo (rodent and non-rodent animal models)

Agrimonia pilosa (AP) and Rhus gall (RG) are traditional medicinal plants. The bioflavonoid composition standardized by HPLC analysis was named APRG64. Despite many studies reported to beneficial bioactivities of AP and RG, very limited range of toxicity tests have documented. So, we did experiment diversely on the toxicity tests of the substance APRG64. Genotoxicity (mammalian chromosomal aberration test, micronoucleus test) against APRG64, acute and sub-chronic toxicity test from rodent/non-rodent, and systemic safety pharmacology test were conducted. As a result of the test, genotoxicity against APRG64 was not observed. The NOAEL of rodents was confirmed as 2000 mg/kg/day and non-rodents was confirmed as 500 mg/kg/day. In addition, systemic safety pharmacological toxicity (effects on respiratory system, central nervous system, cardiovascular system) following administration of APRG64 was not observed. Finally, we accomplished ten potential toxicity tests and evaluated extensive safety of APRG64. Consequently, APRG64 may be a promising material for nutraceuticals and natural medicines.

In planta high levels of hydrolysable tannins inhibit peroxidase mediated anthocyanin degradation and maintain abaxially red leaves of Excoecaria Cochinchinensis

BACKGROUND

Abaxially anthocyanic leaves of deeply-shaded understorey plants play important ecological significance for the environmental adaption. In contrast to the transient pigmentation in other plants, anthocyanins are permanently presented in these abaxially red leaves, however, the mechanism for the pigment maintenance remains unclear. In the present study, we investigated phenolic metabolites that may affect pigment stability and degradation in Excoecaria cochinchinensis (a bush of permanently abaxial-red leaves), via a comparison with Osmanthus fragrans (a bush of transiently red leaves).

RESULTS

High levels of galloylated anthocyanins were identified in the Excoecaria but not in the Osmanthus plants. The galloylated anthocyanin showed slightly higher stability than two non-galloylated anthocyanins, while all the 3 pigments were rapidly degraded by peroxidase (POD) in vitro. High levels of hydrolysable tannins [mainly galloylglucoses/ellagitannins (GGs/ETs)] were identified in Excoecaria but none in Osmanthus. GGs/ETs showed inhibition effect on POD, with IC50 ranged from 35.55 to 83.27 μM, correlated to the markedly lower POD activities detected in Excoecaria than in Osmanthus. Strong copigmentation was observed for GGs/ETs and anthocyanins, with more than 30% increase in the red intensity of non-galloylated anthocyanin solutions. In the leaf tissue, the hydrolysable tannins were observed to be co-localized with anthocyanins at the abaxial layer of the Excoecaria leaves, correlated to the low POD activity, more acidity and increased red intensity of the tissue.

CONCLUSION

The results suggest that the Excoecaria leaves accumulate a distinct group of phenolic metabolites, mainly GGs/ETs, at the abaxial layer, which prevent anthocyanin degradation and increase the pigment stability, and consequently lead to the permanent maintenance of the red leaves.

Two new naphthalenic lactone glycosides from Cassia obtusifolia L. seeds

Two new naphthalenic lactone glycosides, (3S)-9,10-dihydroxy-7-methoxy-3-methyl-1-oxo-3,4-dihydro-1H-benzo[g]isochromene-3-carboxylic acid 9-O-β-D-glucopyranoside (1) and (3R)-cassialactone 9-O-β-D-glucopyranoside (2) were isolated from seeds of Cassia obtusifolia Linn., along with five known compounds: (3R)-cassialactone 9-O-β-D-gentiobioside (3), emodin 1-O-β-gentiobioside (4), 1-hydroxyl-2-acetyl-3,8-dimethoxy-naphthalene 6-O-β-D-apiofuranosyl-(1 → 2)-β-D-glucopyranoside (5), rubrofusarin 6-O-β-D-gentiobioside (6), rubrofusarin 6-O-β-D-triglucoside (7). Structures of 1 and 2 were elucidated by NMR and HR-ESI-MS spectroscopic analysis. Their stereochemistry was determined by CD experiment. All compounds were tested for their ability to inhibit the formation of advanced glycation end-products in vitro. Compounds 1, 2, 3, 5, and 6 showed significant in vitro inhibitory activities (IC₅₀ values of 11.63, 23.40, 7.32, 89.03, and 38.89 µM, respectively).