Two new caffeyol glycosides from Forsythia suspensa

The phytochemistry, pharmacology, pharmacokinetics, quality control, and toxicity of Forsythiae Fructus: A updated systematic review

Forsythiae Fructus (FF), the dried fruit of F. suspensa, is commonly used to treat fever, inflammation, etc in China or other Asian countries. FF is usually used as the core herb in traditional Chinese medicine preparations for the treatment of influenza, such as Shuang-huang-lian oral liquid and Yin-qiao powder, etc. Since the wide application and core role of FF, its research progress was summarized in terms of traditional uses, phytochemistry, pharmacology, pharmacokinetics, quality control, and toxicity. Meanwhile, the anti-influenza substances and mechanism of FF were emphasized. Till now, a total of 290 chemical components are identified in F. suspensa, and among them, 248 components were isolated and identified from FF, including 42 phenylethanoid glycosides, 48 lignans, 59 terpenoids, 14 flavonoids, 3 steroids, 24 cyclohexyl ethanol derivatives, 14 alkaloids, 26 organic acids, and 18 other types. FF and their pure compounds have the pharmacological activities of anti-virus, anti-inflammation, anti-oxidant, anti-bacteria, anti-tumor, neuroprotection, hepatoprotection, etc. Inhibition of TLR7, RIG-I, MAVS, NF-κB, MyD88 signaling pathway were the reported anti-influenza mechanisms of FF and phenylethanoid glycosides and lignans are the main active groups. However, the bioavailability of phenylethanoid glycosides and lignans of FF in vivo was low, which needed to be improved. Simultaneously, the un-elucidated compounds and anti-influenza substances of FF strongly needed to be explored. The current quality control of FF was only about forsythoside A and phillyrin, more active components should be taken into consideration. Moreover, there are no reports of toxicity of FF yet, but the toxicity of FF should be not neglected in clinical applications.

High Value-Added Application of Natural Products in Crop Protection: Discovery and Exploration of Caffeoyl and Flavonoid Derivatives from Clematis brevicaudata DC. as Novel Insecticide Candidates

Nine caffeoyl derivatives (1-9), including two new dicaffeoyl glycosides, brevicaudatosides A and B (1 and 2), and six flavonoids (10-15), were identified from overground Clematis brevicaudata DC. Compounds 1 and 13 exhibited significant oral toxicities against Acyrthosiphon pisum Harris with LC50 (half-lethal concentration) values of 0.12 and 0.28 mM, respectively. Meanwhile, compounds 1, 8, 10, 13, and 15 showed remarkable repellent effects against A. pisum with the repellent indexes valued at 1.00 under 50-200 μg/mL at 24 h. Compounds 1 and 8 also displayed moderate antifeedant activities against Plutella xylostella L. The shrunken bodies, especially for wizened cauda, and the ultrastructural damages of microvilli, mitochondrion, nucleus, and endoplasmic reticulum in midgut were toxic symptoms of A. pisum caused by 1 and 13. The inhibition of Chitinase was the main reason for their potent insecticidal activities. This study provided valuable pieces of evidence for the high value-added application of caffeoyl and flavonoid derivatives from C. brevicaudata as novel plant-origin biopesticides for crop protection.

Plant-Derived Caffeic Acid and Its Derivatives: An Overview of Their NMR Data and Biosynthetic Pathways

In recent years, caffeic acid and its derivatives have received increasing attention due to their obvious physiological activities and wide distribution in nature. In this paper, to clarify the status of research on plant-derived caffeic acid and its derivatives, nuclear magnetic resonance spectroscopy data and possible biosynthetic pathways of these compounds were collected from scientific databases (SciFinder, PubMed and China Knowledge). According to different types of substituents, 17 caffeic acid and its derivatives can be divided into the following classes: caffeoyl ester derivatives, caffeyltartaric acid, caffeic acid amide derivatives, caffeoyl shikimic acid, caffeoyl quinic acid, caffeoyl danshens and caffeoyl glycoside. Generalization of their 13C-NMR and 1H-NMR data revealed that acylation with caffeic acid to form esters involves acylation shifts, which increase the chemical shift values of the corresponding carbons and decrease the chemical shift values of the corresponding carbons of caffeoyl. Once the hydroxyl group is ester, the hydrogen signal connected to the same carbon shifts to the low field (1.1~1.6). The biosynthetic pathways were summarized, and it was found that caffeic acid and its derivatives are first synthesized in plants through the shikimic acid pathway, in which phenylalanine is deaminated to cinnamic acid and then transformed into caffeic acid and its derivatives. The purpose of this review is to provide a reference for further research on the rapid structural identification and biofabrication of caffeic acid and its derivatives.

Fresh and Browned Lotus Root Extracts Promote Cholesterol Metabolism in FFA-Induced HepG2 Cells through Different Pathways

Browning of fresh-cut plants is mainly attributed to the enzymatic browning of phenolic compounds induced by polyphenol oxidase (PPO), producing browning products such as anthraquinones, flavanol oxides, and glycosides, which are usually considered to be non-toxic. Could browning bring any benefits on behalf of their bioactivity? Our previous study found that browned lotus root extracts (BLREs) could reduce the cholesterol level in obese mice as fresh lotus root extracts (FLREs) did. This study aimed to compare the mechanisms of FLRE and BLRE on cholesterol metabolism and verify whether the main component's monomer regulates cholesterol metabolism like the extracts do through in vitro experiments. Extracts and monomeric compounds are applied to HepG2 cells induced by free fatty acids (FFA). Extracellular total cholesterol (TC) and triglyceride (TG) levels were also detected. In addition, RT-PCR and Western blot were used to observe cholesterol metabolism-related gene and protein expression. The in vitro results showed that BLRE and FLRE could reduce TC and TG levels in HepG2 cells. In addition, BLRE suppressed the synthesis of cholesterol. Meanwhile, FLRE promoted the synthesis of bile acid (BA) as well as the clearance and efflux of cholesterol. Furthermore, the main monomers of BLRE also decreased cholesterol synthesis, which is the same as BLRE. In addition, the main monomers of FLRE promoted the synthesis of BAs, similar to FLRE. BLRE and FLRE promote cholesterol metabolism by different pathways.

A novel strategy by integrating chemical profiling, molecular networking, chemical isolation, and activity evaluation to target isolation of potential anti-ACE2 candidates in Forsythiae Fructus

BACKGROUND

Traditional Chinese medicine (TCM) is regarded as a large database containing hundreds to thousands of chemical constituents that can be further developed as clinical drugs, such as artemisinin in Artemisia annua. However, effectively exploring novel candidates is still a challenge faced by researchers.

PURPOSE

In this work, an integrated strategy combining chemical profiling, molecular networking, chemical isolation, and activity evaluation (CMCA strategy) was proposed and applied to systematically characterize and screen novel candidates, and Forsythiae fructus (FF) was used as an example.

STUDY DESIGN

It contained four parts. First, the chemical compounds in FF were detected by ultra-high-performance liquid chromatography-mass spectrometry (UPLC/Q-TOF MS) with data-dependent acquisition, and further, the targeted compounds were screened out based on an in-house database. In the meantime, the representative MS/MS fragmentation behaviors of different chemical structure types were summarized. Second, homologous constituents were grouped and organized based on feature-guided molecular networking, and the nontargeted components with homologous mass fragmentation behaviors were characterized. Third, the novel compounds were isolated and unambiguously identified by nuclear magnetic resonance (NMR). Finally, the anti-angiotensin-converting enzyme 2 (ACE2) activities of isolated chemical constituents were further evaluated by in vitro experiments.

RESULTS

A total of 278 compounds were profiled in FF, including 151 targeted compounds and 127 nontargeted compounds. Among them, 16 were unambitiously identified by comparison with reference standards. Moreover, 25 were classified into potential novel compounds. Two novel compounds were unambiguously identified by using conventional chromatographic methods, and they were named phillyrigeninside D (peak 254) and forsythenside O (peak 155). Furthermore, the ACE2 activity of the compounds in FF was evaluated by modern pharmacological methods, and among them, suspensaside A was confirmed to present obvious anti-ACE2 activity.

CONCLUSION

Our work provides meaningful information for revealing potential FF candidates for the treatment of COVID-19, along with new insight for exploring novel candidates from complex systems.

Neuroprotective and anti-inflammatory phenylethanoidglycosides from the fruits of Forsythia suspensa

Neuroinflammation is emerging as a crucial reason of major neurodegenerative diseases in recent years. Increasingly evidences have supported that bioactive natural products from traditional Chinese medicines have efficiency for neuroinflammation. Forsythia suspensa, a typical medicinal herb, showed potential neuroprotective and anti-inflammatory properties in previous pharmacological studies. In our research to obtain neuroprotective and anti-inflammatory natural products, three unprecedented C6-C7'/C6-C16' linked phenylethanoidglycoside dimers (1-3), three new phenylethanoidglycosides (4-6), and six known compounds (7-12) were isolated from the fruits of Forsythia suspensa. Their structures were determined by comprehensive spectroscopic data and comparison to the literature data. All isolated compounds were evaluated their neuroprotective and anti-inflammatory activities. Compounds 1 and 10 exhibited significant neuroprotective activities with the cell viability values of 75.24 ± 8.05% and 93.65 ± 10.17%, respectively, for the serum-deprivation and rotenone induced pheochromocytoma (PC12) cell injury. Meanwhile, compound 1 exhibited excellent anti-inflammatory activity against tumor necrosis factor (TNF)-α expression in LPS induced RAW264.7 cells with the IC₅₀ value of 1.30 μM. This study revealed that the bioactive phenylethanoidglycosides may attenuate neuroinflammation through their neuroprotective and anti-inflammatory activities.

Phytochemistry, pharmacology, quality control and future research of Forsythia suspensa (Thunb.) Vahl: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Forsythiae Fructus (called Lianqiao in Chinese), the fruit of Forsythia suspensa (Thunb.) Vahl, is utilized as a common traditional medicine in China, Japan and Korea. It is traditionally used to treat pyrexia, inflammation, gonorrhea, carbuncle and erysipelas. Depending on the different harvest time, Forsythiae Fructus can be classified into two forms, namely Qingqiao and Laoqiao. The greenish fruits that start to ripen are collected as Qingqiao, while the yellow fruits that are fully ripe are collected as Laoqiao. Both are applied to medical use. This review aims to provide a systematic summary of F. suspensa (Forsythia suspensa (Thunb.) Vahl) and to reveal the correlation between the traditional uses and pharmacological activities so as to offer inspiration for future research.

MATERIALS AND METHODS

All corresponding information about F. suspensa was searched by Scifinder and obtained from scientific databases including Springer, Science Direct, Wiley, Pubmed and China Knowledge Resource Integrated (CNKI). Local dissertations and books were searched as well.

RESULTS

According to classical Chinese herbal texts and Chinese Pharmacopoeia, Forsythiae Fructus dominantly displays heat-clearing and detoxifying effects in TCM prescriptions. In modern research, more than 230 compounds were separated and identified from F. suspensa. 211 Of them were isolated from fruits. Lignans and phenylethanoid glycosides are considered as the characteristic and active constituents of this herb, such as forsythiaside, phillyrin, rutin and phillygenin. They exhibited anti-inflammatory, antioxidant, antibacterial, anti-virus, anti-cancer and anti-allergy effects, etc. Currently, there is no report on the toxicity of Forsythiae Fructus, despite slight toxicity of forsythiaside reported in local publications. Compared to Laoqiao, Qingqiao contains higher levels of forsythiaside, forsythoside C, cornoside, rutin, phillyrin, gallic acid and chlorogenic acid and lower levels of rengyol, β-glucose and S-suspensaside methyl ether.

CONCLUSION

Heat-clearing actions of Forsythiae Fructus are based on the anti-inflammatory and antioxidant properties of lignans and phenylethanoid glycosides. Detoxifying effects attribute to the antibacterial, antiviral and anti-cancer activities of Forsythiae Fructus. And traditional Chinese medicine (TCM) characteristics of Forsythiae Fructus (bitter flavor, slightly cold nature and lung meridian) supported its strong anti-inflammatory effects. In addition, the remarkable anti-inflammatory and antioxidant capacities of Forsythiae Fructus contribute to its anti-cancer and neuroprotective activities. The higher proportion of lignans and phenylethanoid glycosides in Qingqiao than Laoqiao might explain the better antioxidant ability of Qingqiao and more frequent uses of Qingqiao in TCM prescriptions. For future research, more in vivo experiments and clinical studies are encouraged to further clarify the relation between traditional uses and modern applications. Regarding to Qingqiao and Laoqiao, they remain to be differentiated by all-round quality control methods, and the chemical compositions and clinical effects between them should be compared.

UPLC-QTOF-MSE -based diagnostic product ion filtering to unveil unstable C6 -C2 glucoside conjugates in Forsythia suspensa

Forsythia suspensa contains C₆ -C₂ glucoside conjugates (CCGCs) that are chemically unstable, thereby hindering their isolation and purification. In the present study, ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF) was utilized to screen and identify unstable CCGCs in the fruits and leaves of F. suspensa without any tedious isolation and purified process based on independent information acquisition (also called MS^E ) and individual MS/MS experiments. Diagnostic product ion filtering (DPIF) was further applied to mine unknown analogs in MS^E high energy levels based on characteristic m/z of key substructures. A modified nomenclature for CCGCs is hereby proposed to facilitate discussions. Possible fragmentation pathways of major types of known CCGCs were proposed and used for deducing their structures. A total of 8 potentially new CCGCs were discovered and initially identified. The accuracy of their identification was further verified by structural elucidation of 3 unstable CCGCs isolated from the fruits of F. suspensa using 1D and 2D-NMR spectroscopy. The established UPLC-QTOF-MS^E -based DPIF technique facilitates the rapid discovery and direct identification of unstable CCGCs in fruits and leaves of F. suspensa.

Forsythiae Fructus: A Review on its Phytochemistry, Quality Control, Pharmacology and Pharmacokinetics

Forsythiae Fructus, as a traditional Chinese medicine, has been widely used both as a single herb and in compound prescriptions in Asia, mainly due to its heat-clearing and detoxifying effects. Modern pharmacology has proved Forsythiae Fructus possesses various therapeutic effects, both in vitro and in vivo, such as anti-inflammatory, antibacterial and antiviral activities. Up to now, three hundred and twenty-one compounds have been identified and sensitive analytical methods have been established for its quality control. Recently, the pharmacokinetics of Forsythiae Fructus and its bioactive compounds have been reported, providing valuable information for its clinical application. Therefore, this systematic review focused on the newest scientific reports on Forsythiae Fructus and extensively summarizes its phytochemistry, pharmacology, pharmacokinetics and standardization procedures, especially the difference between the two applied types—unripe Forsythiae Fructus and ripe Forsythiae Fructus—in the hope of providing a helpful reference and guide for its clinical applications and further studies.

Two new phenolic acids from the fruits of Forsythia suspense

Two new phenolic acids forsythiayanoside C (1) and forsythiayanoside D (2), were isolated from the fruits of Forsythia suspense (Thunb.) Vahl. Their structures were elucidated on the basis of chemical and spectral analysis, including 1D, 2D NMR analyses, HRESIMS and CD spectrometry. The cytotoxic and antioxidant activities testing showed that compound 2 exhibited free radical scavenging activity.

Comparison of Fruits of Forsythia suspensa at Two Different Maturation Stages by NMR-Based Metabolomics

Forsythiae Fructus (FF), the dried fruit of Forsythia suspensa, has been widely used as a heat-clearing and detoxifying herbal medicine in China. Green FF (GF) and ripe FF (RF) are fruits of Forsythia suspensa at different maturity stages collected about a month apart. FF undergoes a complex series of physical and biochemical changes during fruit ripening. However, the clinical uses of GF and RF have not been distinguished to date. In order to comprehensively compare the chemical compositions of GF and RF, NMR-based metabolomics coupled with HPLC and UV spectrophotometry methods were adopted in this study. Furthermore, the in vitro antioxidant and antibacterial activities of 50% methanol extracts of GF and RF were also evaluated. A total of 27 metabolites were identified based on NMR data, and eight of them were found to be different between the GF and RF groups. The GF group contained higher levels of forsythoside A, forsythoside C, cornoside, rutin, phillyrin and gallic acid and lower levels of rengyol and β-glucose compared with the RF group. The antioxidant activity of GF was higher than that of RF, but no significant difference was observed between the antibacterial activities of GF and RF. Given our results showing their distinct chemical compositions, we propose that NMR-based metabolic profiling can be used to discriminate between GF and RF. Differences in the chemical and biological activities of GF and RF, as well as their clinical efficacies in traditional Chinese medicine should be systematically investigated in future studies.

Two new glycosides from the fruits of Forsythia suspense

Two new glycosides suspensaside C (1) and 2,3,5,6-tetrahydro-jacaranone-4-O-β-D-glucopyranoside (2), together with four known compounds suspensaside A (3), rengynic acid-1'-O-β-D-glucopyranoside (4), forsythoside A (5), and rengynic acid (6), were isolated from the fruits of Forsythia suspense (Thunb.) Vahl. The structures of 1 and 2 were elucidated on the basis of chemical and spectral analysis, including 1D, 2D NMR analyses and HR-ESI-MS. All isolates were tested for their cytotoxicities against five human cancer cell lines (A549, Colo-205, Hep-3B, HL60, and KB). Compound 3 exhibited cytotoxicity against HL-60, Hep-3B, and A549 cancer cell lines.

Assessment and modulation of forsythiaside absorption with MDCKII cells and validation with in situ intestinal experiment

Forsythiaside was characterized by low intestinal absorption by in situ rat experiment and Caco-2 cells. The mechanisms behind this low absorption had not yet been elucidated. The purpose of this study was to investigate the role of efflux transporters in the intestinal absorption of forsythiaside as a potential mechanism for its low small-intestinal absorption following oral administration. Polarized MDCKII cell lines stably transfected with human or murine complementary DNA encoding for various efflux transporters (P-gp/MDR1, MRP2 and Bcrp1) were used to study transepithelial transport of forsythiaside and compare results with the MDCKII-Wild type cells. The transportation inhibitors GF120918, MK571 and Ko143 were used to investigate the transport mechanism. The active transport of forsythiaside was found in MDCKII-WT cells. The MDCKII-MRP2 and MDCKII-Bcrp1 cells significantly increased forsythiaside efflux ratio compared with the parental cells due to the apically directed transport by MRP2 and Bcrp1, respectively. The efflux ratios in MRP2 and Bcrp1 transfected cell lines were greatly decreased in the presence of MK-571 and Ko143, respectively, which indicated that forsythiaside efflux by MRP2 and Bcrp1 were significantly inhibited by their selective inhibitors. MDCKII-MDR1 cells did not exhibit a significant reduction in the forsythiaside efflux compared with the parental cells, indicating that it was not a good substrate for MDR1. And the results were then validated by the in situ experiment. This study presents direct evidence that forsythiaside is effluxed by both MRP2 and Bcrp1, which may contribute to its poor oral bioavailability.

Protective effects of Forsythia suspensa extract against oxidative stress induced by diquat in rats

Forsythia suspensa extract has been proved as a potential antioxidant in the recent years. The present study was undertaken to obtain the optimal antioxidant fraction in vitro and examine its antioxidative potential against diquat-induced oxidative stress in male Sprague Dawley rats in vivo. In vitro, 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging experiment indicated that the CH2Cl2 fraction of F. suspensa (FSC) exerted the strongest scavenging activities; forsythoside A, forythialan A and phillygenin from it might be the major antioxidant constituents. In vivo, pretreatment of rats with different doses of FSC (25, 50 and 100 mg/kg bw) and vitamin C (100 mg/kg bw, positive control) for 15 days significantly lowered the tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6) in plasma compared to the negative control group. Also, FSC significantly increased the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and the levels of glutathione (GSH) in plasma, liver and kidney whereas it decreased the levels of malondialdehyde (MDA) in plasma and kidney. Moreover, the protective effect of FSC (100 mg/kg bw) was better than vitamin C. These results revealed that FSC exerted a protective effect against diquat-induced oxidative stress and is worthy of becoming a potential dietary antioxidant.

New phenylethanoid glycosides from the fruits of forsythia suspense (thunb.) vahl

Forsythosides H-J (1-3), three new caffeoyl phenylethanoid glycosides (CPGs), were isolated from the fruits of Forsythia suspense (Thunb.) Vahl., together with six known phenylethanoid glycosides: Forsythoside A (4), Forsythoside F (5), Forsythoside E (6), 2-(3,4-dihydroxyphenyl)ethyl-beta-D-glucopyranoside (7), phenethyl alcohol beta-D-xylo-pyranosyl-(1-->6)-beta-D-glucopyranoside (8) and calceolarioside B (9). Their structures were determined by spectroscopic and chemical methods.

Characterization of phenolic compounds in the fruits of Forsythia suspensa by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry

Phenolic compounds are the major bioactive constituents of Forsythia suspensa, an important Chinese herbal medicine used for the treatment of various infectious diseases. Fragmentation behaviors of the phenolic compounds in F. suspensa were investigated by using a high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS(n)) method. For common phenylethanoid glycosides, the loss of the caffeoyl moiety was the first fragmentation step, then sequential losses of rhamnose, hexose and water were observed in further fragmentations. If a substituent group presented in the beta position, the fragmentation was triggered by initial loss of a substituent group to form structures such as suspensaside A. Then it underwent the common fragmentation pathways as mentioned above, or eliminated characteristic residues of masses 134 or 152 Da, respectively. The latter pathway is reported here for the first time. The fragmentation behaviors of furofuran lignans displayed a typical cleavage of the tetrahydrofuran ring. However, the presence of a hydroxyl group at C-1 led to the successive loss of 30 Da. Neutral loss of CO(2) and benzyl cleavage were characteristic for lignans with a 2,3-dibenzylbutyrolactone skeleton. A neutral loss of 30 Da was also observed in the fragmentation pattern of flavonols. These fragmentation rules were implemented to analyze phenolic compounds in the fruits of F. suspensa. A total of 51 compounds, including 24 phenylethanoid glycosides, 21 lignans and 6 flavonols, were identified or tentatively characterized based on their retention times, UV spectra and MS fragmentation patterns.

Simultaneous determination of 12 major constituents in Forsythia suspensa by high performance liquid chromatography--DAD method

A high performance liquid chromatographic method was developed to simultaneously determine the 12 major constituents of Forsythia suspensa, namely R-suspensaside, S-suspensaside, S-suspensaside methyl ether, (+)-pinoresinol-beta-d-glucoside, forsythiaside, (+)-epipinoresinol-4'-O-glucoside, suspensaside A, rutin, phillyrin, (+)-pinoresinol, (+)-epipinoresinol and phillygenin. The HPLC assay was performed on a Zorbax XDB C(18) column with gradient elution of methanol and 0.3% aqueous acetic acid within 55 min. The detection wavelength was 280 nm. All the compounds showed good linearity (r(2)>0.9998). The method was reproducible with intra- and inter-day variation less than 3%. The recovery of the assay was in the range of 91.2-104.9%. The method was successfully applied to the quantification of 12 constituents in 33 F. suspensa samples. The results indicated that the developed assay could be considered as a suitable quality control method for F. suspensa.

Vasorelaxant Effects of Forsythiaside from the Fruits of Forsythia suspensa

The vasorelaxant effects of forsythiaside (compound 1) from the fruits of Forsythia suspensa on isolated rat aortic rings were studied. Compound 1 showed a slow relaxation activity against norepinephrine (NE)-induced contractions of rat aorta with/without endothelium. This compound did not affect contractions induced by a high concentration of potassium (K(+) 60 mM), while it inhibited NE-induced vasocontraction in the presence of nicardipine. These results show that the inhibition by compound 1 of NE-induced vasocontraction is due to a decrease in calcium influx from the extracellular space caused by NE.