Coumarins and flavones with anti-inflammatory activity isolated from the branches and leaves of Daphne retusa.

In this study, two new (1, 13) and fourteen known (2-12, 14-16) compounds were isolated from the branches and leaves of Daphne retusa. On the basis of chemical evidence and spectral data analysis (UV, ECD NMR, and HR-ESI-MS), the structures of new compounds were elucidated. Furthermore, all compounds have been tested for their inhibitory effects on NO production in LPS-induced RAW 264.7 cells, and compound 3 showed obvious inhibitory effect. Through target screening and molecular docking technology, potential binding targets for compound 3 to exert anti-inflammatory effects have been predicted.

Red Room-Temperature Phosphorescence Supramolecular Assemblies Based on Cucurbit[7]uril: Reversible Temperature Stimulation Response and Cell-Specific Silver Ion Imaging.

Solid-state materials with efficient room-temperature phosphorescence (RTP) emission have been widely used in materials science, and organic RTP-emitting systems with heavy-metal doping in aqueous solutions have attracted much attention in recent years. A novel supramolecular interaction was induced by host-guest assembly using cucurbit[7]uril (Q[7]) as the host and brominated naphthalimide phosphor as the guest. This interaction was further enhanced through synergistic chelation stimulated by analytical silver ion complexation. This approach facilitated the system's structural rigidity, intersystem crossing, and oxygen shielding. We achieved deep red phosphorescence emission in aqueous solution and ambient conditions along with quantitative determination of silver ions. The new complex exhibited good reversible thermoresponsive behavior and was successfully applied for the first time to target phosphorescence imaging of silver ions in the mitochondria of A549 cancer cells. These results are beneficial for constructing novel RTP systems with stimulus-responsive luminescence in aqueous solution, contributing to future research in bioimaging, detection, optical sensors, and thermometry materials.

Cucurbit[7]uril-based carbon dots for recognizing histamine.

Fluorescent carbon quantum dots (CQDs) were synthesized from cucurbit[7]uril (Q[7]) and 2,2-bis(hydroxymethyl)propionic (DMPA) by a hydrothermal method. The Q[7]-DMPA complex was confirmed by X-ray crystallography. The CQDs showed blue fluorescence, photostability, and ionic strength stability. They were used to detect histamine with a low limit of 2.33 × 10-6 M.

Metal Cation-Doped ns-Cucurbit[10]uril: Adsorption of Para-Phenylenediamine.

The separation of phenylenediamine (PDA) isomers is crucial in the field of chemical manufacturing. Herein, we presented a strategy for the separation of PDA isomers (para-phenylenediamine, p-PDA; meta-phenylenediamine, m-PDA; ortho-phenylenediamine, o-PDA) using four supramolecular framework materials of ns-cucurbit[10]uril (ns-Q[10]), (1) ns-Q[10](Cd), (2) ns-Q[10](Mn), (3) ns-Q[10](Cu), (4) ns-Q[10](Pb). Our findings indicated that these supramolecular framework materials of ns-Q[10] showed remarkable selectivity for para-phenylenediamine (p-PDA) in p-PDA, m-PDA, and o-PDA mixtures, respectively. The variations in selectivity observed in these four single-crystal structures arose from variations in the thermodynamic stabilities and binding modes of the host-guest complexes. Importantly, the supramolecular framework based on ns-Q[10] exhibited selective accommodation of p-PDA over its isomers. This study highlighted the practical application of ns-Q[10] in effectively separating PDA isomers and demonstrated the potential utility of ns-Q[10] in isolating other organic molecules.

Three New Labdane-Type Diterpenoids from the Fruits of Amomum villosum and Their Anti-Inflammatory Activities.

Three new labdane-type diterpenoids, calcaratarin E, villosumtriol, and 12-epi-villosumtriol (1-3) were isolated from the fruits of Amomum villosum, along with seven known diterpenoids (4-10). Through comprehensive analysis of chemical evidence and spectral data including UV, 1D and 2D NMR, HR-ESI-MS, IR, and X-ray crystallography, the structures of these novel compounds were successfully determined. Additionally, the inhibitory effects of compounds 2-10 on NO production in lipopolysaccharide (LPS)-induced RAW264.7 cells were evaluated. Notably, compound 6 exhibited the most significant inhibitory effect with an IC50 value of 1.74±0.69 µM.

CD44-Targeted Photoactivatable Polymeric Nanosystem with On-Demand Drug Release as a "Photoactivatable Bomb" for Combined Photodynamic Therapy-Chemotherapy of Cancer.

Nowadays, the combined use of chemotherapy and photodynamic therapy (PDT) remains the most popular strategy for cancer treatment with high theraprutic efficacy. However, targeted therapy with the on-demand release of drugs is what most clinical treatments lack, leading to heavy side effects. Herein, a new CD44-targeted and red-light-activatable nanosystem, Ru-HA@DOX nanoparticles (NPs), was developed by conjugating hydrophilic biodegradable hyaluronic acid (HA) and hydrophobic photoresponsive ruthenium (Ru) complexes, which could encapsulate the chemotherapeutic drug doxrubicin (DOX). Ru-HA@DOX NPs can selectively accumulate at the tumor through the enhanced permeability and retention (EPR) effect and CD44-mediated endocytosis, thus avoiding off-target toxicity during circulation. After 660 nm of irradiation at the tumor site, Ru-HA@DOX NPs, as a "photoactivatable bomb", was split via the photocleavable Ru-N coordination bond to fast release DOX and produce singlet oxygen (1O2) for PDT. In general, Ru-HA@DOX NPs retained its integrity before irradiation and possessed minimal cytotoxicity, while under red-light irradiation, Ru-HA@DOX NPs showed significant cytotoxicity due to the release of DOX and production of 1O2 at the tumor. Chemotherapy-PDT of Ru-HA@DOX NPs resulted in a significant inhibition of tumor growth in A549-tumor-bearing mice and reduced the cardiotoxicity of DOX. Therefore, this study offers a novel CD44-targeted drug-delivery system with on-demand drug release for synergistic chemotherapy-PDT.

Anomanolide C suppresses tumor progression and metastasis by ubiquitinating GPX4-driven autophagy-dependent ferroptosis in triple negative breast cancer.

Anomanolide C (AC), a natural withanolide isolated from Tubocapsicum anomalum, has been reported to have exhibits remarkable anti-tumour activities in several types of human cancers, particularly triple-negative breast cancer (TNBC). However, its intricate mechanisms still remain need to be clarified. Here, we evaluated whether AC could inhibit cell proliferation and the role of AC in ferroptosis induction and autophagy activation. Subsequently, the anti-migration potential of AC was found via autophagy-dependent ferroptosis. Additionally, we found that AC reduced the expression of GPX4 by ubiquitination and inhibited TNBC proliferation and metastasis in vitro and in vivo. Moreover, we demonstrated that AC induced autophagy-dependent ferroptosis, and led to Fe2+ accumulation via ubiquitinating GPX4. Moreover, AC was shown to induce autophagy-dependent ferroptosis as well as to inhibit TNBC proliferation and migration via GPX4 ubiquitination. Together, these results demonstrated that AC inhibited the progression and metastasis of TNBC by inducing autophagy-dependent ferroptosis via ubiquitinating GPX4, which might shed light on exploiting AC as a new drug candidate for the future TNBC therapy.

Irisin Attenuates Apoptosis Following Ischemia-Reperfusion Injury Through Improved Mitochondria Dynamics and ROS Suppression Mediated Through the PI3K/Akt/mTOR Axis.

Irisin is a muscle-derived hormone that promotes the survival of motor neurons and enhances muscle size following injury. In this study, we investigated the beneficial effects and mechanism(s) of action of irisin in response to cerebral ischemia-reperfusion injury (CIRI). Right-middle cerebral artery occlusion (MCAO) and hypoxia/reoxygenation (H/R) models were generated in C57BL/6 J mice. Mouse neuronal cell lines (NSC-34) were used to confirm the molecular mechanisms of the protection afforded by irisin in response to CIRI. We found that irisin (250 µg/kg) improved cerebral function and reduced the cerebral infarct volume following CIRI. Irisin also protected neuronal cells against ischemia-reperfusion (I/R) induced apoptosis, assessed via TUNEL, and cleaved Caspase-3 staining. Western blotting of neuronal tissue from irisin treated I/R mice showed lower expression of pro-apoptotic Bax and caspase-9 (P < 0.001 and P < 0.01) and increased levels of the pro-survival protein Bcl-2 (P < 0.01 & P < 0.001 vs. I/R). Irisin also reduced the levels of reactive oxygen species (ROS) characterized through malondialdehyde (MDA) assays. Irisin was found to maintain mitochondrial homeostasis through the suppression of mitochondrial fission-linked dynamin-related protein 1 in CIRI mice (P < 0.01 and P < 0.05 v. I/R cohort). Moreover, mitochondrial fusion-related protein (Mfn2) and Opa1 expression were rescued following irisin treatment (P < 0.001 and P < 0.01 v. I/R cohort). Cell-based assays showed that irisin activates PI3K/AKT/mTOR signaling in the neurons of CIRI mice. Furthermore, the beneficial effects of irisin on NSC-34 cell-survival, mitochondrial function, and ROS generation were reversed by VS-5584, a highly specific PI3K/AKT/mTOR inhibitor. Collectively, these data highlight the ability of irisin to alleviate CIRI in vivo and in vitro. The mechanisms of action of irisin include the attenuation of apoptosis through the prevention of mitochondrial fission and increased mitochondrial fusion and the alleviation of oxidative stress through activation of the PI3K/AKT/mTOR axis. We therefore identify irisin as a much-needed therapeutic for CIRI.

In-vitro and In-vivo Identification, Absorbtion and Metabolism Network Analysis of Filifolium sibiricum Flavonoids Dropping Pill by UHPLC-Q-TOF-MS.

BACKGROUND: Filifolium sibiricum flavonoids dropping pill (FSFp), a unique Chinese Filifolii sibirici herba extract preparation, has the potential as an alternative therapy against S. aureus infection (SA) and antiinfection. However, its chemical composition and in vivo metabolism characteristics remain unknown, which limits its clinical application. METHODS: Here, we aimed to understand the in vitro and in vivo material basis of FSFp. Ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) was used to identify chemicals in FSFp as well as its phase I and phase II reaction metabolites in plasma, urine and feces. RESULTS: A total of 38 chemicals were characterized in FSFp, including 22 flavonoids, 10 organic acids, 3 chromones, 1 aromatic ketone, 1 coumarin, and 1 ligan. After analysis of the drugged bio-samples, a total of 21 compounds were found in urine, and 16 of them were found in feces, but only one was found in plasma. In addition, 56 FSFp-related metabolites were characterized, of which 56 were in urine, 4 in feces, and 8 in plasma. CONCLUSION: This is the first comprehensive research of FSFp on chemical constituents and metabolic profiles. It was expected that this study would offer reliable support for further investigation of FSFp.

Ginsenoside Rg1 in neurological diseases: From bench to bedside.

Ginseng has been used in China as a superior medicinal material for thousands of years that can nourish the five internal organs, calm the mind and benefit wisdom. Due to its anti-inflammatory, antioxidant and neuroprotective activities, one of the active components of ginseng, ginsenoside Rg1, has been extensively investigated in the remedy of brain disorders, especially dementia and depression. In this review, we summarized the research progress on the action mechanisms of Rg1 ameliorating depression-like behaviors, including inhibition of hyperfunction of hypothalamic-pituitary-adrenal (HPA) axis, regulation of synaptic plasticity and gut flora. Rg1 may alleviate Alzheimer's disease in the early phase, as well as in the middle-late phases through repairing dendrite, axon and microglia- and astrocyte-related inflammations. We also proposed that Rg1 could regulate memory state (the imbalance of working and aversive memory) caused by distinct stimuli. These laboratory studies would further the clinical trials on Rg1. From the prospective of drug development, we discussed the limitations of the present investigations and proposed our ideas to increase permeability and bioavailability of Rg1. Taken together, Rg1 has the potential to treat neuropsychiatric disorders, but a future in-depth investigation of the mechanisms is still required. In addition, drug development will benefit from the clinical trials in one specific neuropsychiatric disorder.

Anti-infammatory scalemic chromanoids and chromenoids from Rhododendron dauricum.

Four pairs of undescribed chromane and chromene meroterpenoid scalemic mixtures (1a/1b-4a/4b), together with three pairs of known chromane meroterpenoid ones (5a/5b-7a/7b) were isolated from the twigs and leaves of Rhododendron dauricum L. Among them, 1a/1b-3a/3b and 5a/5b-7a/7b were the chromane ones derived from an intramolecular [2 + 2] cyclic addition of their respective chromene precursors, forming a 6/6/6/4 and 6/6/5/4 ring fused scaffold. The absolute configurations of the chiral center at C-15 of 2a/2b were determined by Snatzke's method, and comparing the experimental and calculated electronic circular dichroism (ECD) data. The inhibitory effects of the isolated compounds were tested against lipopolysaccharide (LPS)-induced nitric oxide production in RAW264.7 macrophage cells to evaluate their anti-inflammatory activity. Compounds 4a, 4b and 6a displayed inhibitory effects on nitric oxide (NO) production, and compound 4b exhibited the obvious anti-inflammatory activity, with an IC50 value of 6.91 ± 0.97 µM, by downregulating nuclear factor kappa B (NF-κB) and reducing the expression of inducible nitric oxide synthase (iNOS) in LPS-induced RAW264.7 cells. These results intimated that 4b could be used as a leading compound to develop anti-inflammatory drugs and is worthy of further investigated.

[Lignans from Agrimonia pilosa].

Thirteen lignans were isolated from 60% ethanol extract of Agrimonia pilosa by column chromatography over silica gel, ODS, and MCI and preparative high performance liquid chromatography(HPLC). Their chemical structures were identified by physiochemical properties and spectral data as(7S,8S)-threo-4,7,9,9'-tetrahydroxy-3,3',5'-trimethoxy-8-O-4'-neolignan(1),(+)-4,9,9'-trihydroxy-3-methoxy-3',7-epoxy-8,4'-oxyneolignan(2), dihydrodehydro-diconiferyl alcohol(3), 4,9,9'-trihydroxy-3,3',5-trimethoxy-4',7-epoxy-8,5'-neolignan(4),(-)-secoisolariciresinol(5), 4,7,9,9'-tetrahydroxy-3,3',5'-trimethoxy-8-O-4'-neolignan(6),(+)-isolariciresinol(7), 4,7,9,9'-tetrahydroxy-3,3'-dimethoxy-8-O-4'-neolignan(8), burselignan(9),(-)-evofolin B(10), icariol A2(11), ciwujiatone(12), and(+)-4″,4-dihydroxy-3,3',3″,3,5,5'-hexamethoxy-7,9';7',9-diepoxy-4,8″;4',8-bisoxy-8,8'-dineolignan-7″,7,9″,9-tetraol(13). Compound 1 was a new compound, and compounds 1-13 were isolated from Agrimonia plant for the first time. This study can enrich the chemical components in A. pilosa and provide material conditions for the follow-up study of its biological activity and the elucidation of its pharmacodynamic substances.

Two New Nor-seco-Isodhilarane-Type Meroterpenoids from the Endophytic Fungus Penicillium purpurogenum.

Two new nor-seco isodhilarane meroterpenoids (NSIMs), purpurogenolides F (1) and G (2), along with three known meroterpenoid analogs (3-5), were isolated from the cultures of an endophytic fungus, Penicillium purpurogenum. Structures and absolute configurations of the new NSIMs were determined based on extensive spectroscopic data analyses, including HR-ESI-MS, UV, IR, NMR chemical shift calculations together with DP4+ probability analysis, as well as ECD calculations. All the isolated meroterpenoids were assessed for their anti-inflammatory activities, and compound 4 exhibited moderate inhibitory activity against the nitric oxide (NO) production in lipopolysaccharide (LPS) induced RAW 264.7 cells with an IC50 value of 20.85±2.31 µM.

CdS-Based Catalysts Derived from TMeQ[6]/[CdxCly]n--Based Frameworks for Oxidation Benzylamine.

The anion-induced outer surface interaction of Q[n]s is an important driving force in the construction of Q[n]-based supramolecular frameworks. In this work, a symmetric tetramethyl-substituted cucurbit[6]uril (TMeQ[6]) is selected as the basic structural block. Using the anion-induced outer surface interaction of Q[n]s derived from [CdxCly]n- anions formed by Cd2+ cations in a HCl medium, four different TMeQ[6]-[CdxCly]n--based supramolecular frameworks are constructed. Three of the most common TMeQ[6]-[CdxCly]n--based supramolecular frameworks are selected for further vulcanization, and three different CdS/TMeQ[6]-based framework catalysts with different structures and properties are obtained. The catalytic activities of these three CdS/TMeQ[6]-based framework catalysts are investigated by the coupling photocatalytic reaction of aminobenzyl, and the results showed that the catalytic activities of the three catalysts are all higher than that of pure CdS. Therefore, this work establishes that it is possible to establish a method for synthesizing the Q[n]-based framework-supported catalysts by first synthesizing TMeQ[6]-[CdxCly]n--based supramolecular frameworks and then forming Q[n]-based framework supported catalysts by sulfurization or reduction.

Natural withanolides, an update.

Covering: March 2010 to December 2020. Previous review: Nat. Prod. Rep., 2011, 28, 705This review summarizes the latest progress and perspectives on the structural classification, biological activities and mechanisms, metabolism and pharmacokinetic investigations, biosynthesis, chemical synthesis and structural modifications, as well as future research directions of the promising natural withanolides. The literature from March 2010 to December 2020 is reviewed, and 287 references are cited.

Natural soluble epoxide hydrolase inhibitors from Inula britanica and their potential interactions with soluble epoxide hydrolase: Insight from inhibition kinetics and molecular dynamics.

Soluble epoxide hydrolase (sEH) is a potential drug target to treat inflammation and neurodegenerative diseases. In this study, we found that the extract of Inula britanica exhibited significantly inhibitory effects against sEH, therefore, we investigated its phytochemical constituents to obtain seven new compounds together with sixteen known ones (1-20), including two pairs of novel enantiomers, (2S,3S)-britanicafanin A (1a), (2R,3R)-britanicafanin A (1b), (2R,3S)-britanicafanin B (2a), and (2S,3R)-britanicafanin B (2b), and three new lignans britanicafanins C-E (3-5). Their structures were determined by HRESIMS, 1D and 2D NMR, and electronic circular dichroism (ECD) spectra as well as quantum chemical computations. All the isolates were evaluated for their inhibitory effects against sEH, compounds 1-3, 5-7, 9, 10, 13, 14, and 17-20 showed significant inhibitory effects against sEH with IC50 values from 3.56 µM to 26.93 µM. The inhibition kinetics results indicated that compounds 9, 10, 13, and 19 were all uncompetitive inhibitors, and their inhibition constants (Ki) values were 7.11, 1.99, 4.06, and 8.78 µM, respectively. Their potential interactions were analyzed by molecular docking and molecular dynamics (MD), which suggested that amino acid residues Asp335 and Asn359, especially Gln384, played an important role in the inhibition of compounds 10 and 13 on sEH, and compounds 10 and 13 could be considered as the potential candidates for the development of sEH inhibitors.

Identification and treatment of a cervical sinus tract in a patient with 10 years of infertility.

OBJECTIVE: To introduce a special case of endometrial cavity fluid (ECF), highlighting the application of hysteroscopy and laparoscopic surgical techniques in the treatment of cervical sinus tract. DESIGN: Narrated video featuring the diagnosis and surgical management of a case of recurrent ECF. Informed consent was obtained from the patient, and approval was granted by the ethics committee of the First Affiliated Hospital of the Wenzhou Medical University. SETTING: Academic tertiary hospital. PATIENT(S): A 36-year-old woman, gravida 0, had menstrual spotting for 13 years after abdominal myomectomy of a 104 × 86 × 111-mm myoma on the posterior uterine wall near the cervix. She failed to conceive after her marriage for 10 years, and 5 operations, including hysteroscopy and laparoscopy, were performed to increase pregnancy opportunities. She also underwent in vitro fertilization and embryo transfer procedures many times, but failed. Transvaginal sonography preoperatively suggested that ECF sometimes appeared and sometimes disappeared. The local echo of the posterior wall of the cervix was enhanced. A 40-mm cystic dark area was found beside the right ovary, which seemed to connect with the cervical hyperechoic part. Additionally, a solid mass of the right adnexa with abundant blood supply was detected. INTERVENTION(S): First, hysteroscopy was performed to explore the ECF. A deep and narrow cervical sinus with a steady stream of accumulated blood overflowed in the lower part of the cervix, and a normal uterine cavity was found. Laparoscopic adhesiolysis and enucleation of the cystic structure that connected to the sinus tract then were performed. Hysteroscopy was repeated to determine the thinnest cervical region by the light transmission test. A horizontal incision was made on the thinnest layer. Scar tissues were removed. The incision was sutured in full layer intermittently and continuously under laparoscopy. The postoperative thickness of the muscular layer in the sinus was confirmed by light transmission test of hysteroscopy. The patient was discharged on the third day after operation, uneventfully. Histopathologic examination showed that the cystic structure and scar tissue contained smooth muscle tissue and were covered by both mucinous columnar epithelium of the cervical canal and endometrial glandular epithelium. MAIN OUTCOME MEASURE(S): Restoration of normal anatomy, removal of uterine effusion, and symptomatic relief. RESULT(S): At the 6-month follow-up, the patient's menstrual cycles returned to normal without the recurrence of menstrual spotting. The ultrasound scan also showed a symmetrical uterus without ECF. CONCLUSION(S): Patients with ECF who underwent assisted reproductive surgeries were related to the poor prognosis. However, the treatment should be different according to the causes, appearance time, and accumulation amount, including expectant treatment, postponement of embryo transfer, transvaginal aspiration, laparoscopic salpingectomy, or proximal tubal occlusion. For patients with recurrent ECF and/or special appearance on ultrasound, endoscopic examination is necessary. In addition, patients with large myomas at difficult locations required a uniform strategy to reduce the intraoperative and postoperative complications, especially for the nulligravida women.

Withanolides isolated from Tubocapsicum anomalum and their antiproliferative activity.

Seven undescribed withanolides (1-7) and six artificial withanolides (8-13), along with 20 known compounds (14-33) were isolated from the aerial parts of Tubocapsicum anomalum. Their structures were confirmed by comprehensive spectroscopic analyses. The absolute configuration of compound 1 was defined by single-crystal X-ray crystallography. All isolates were evaluated for their antiproliferative effects against five human tumor cell lines (Hep3B, MDA-MB-231, SW480, HCT116 and A549), among which compound 24 (tubocapsanolide A) exhibited the highest activities against the MDA-MB-231 cells with an IC50 value of 1.89 ± 1.03 µM. Further studies showed that 24 exhibited significant damage to mitochondria in MDA-MB-231 cells, including excess reactive oxygen species, decreased mitochondrial membrane potential, and apoptosis initiation. In addition, compound 24 also inhibited cell migration. These findings show that tubocapsanolide A may be a promising molecule for triple-negative breast cancer treatment and merit further evaluation.

Cucurbit[n]uril-Based Supramolecular Frameworks Assembled through Outer-Surface Interactions.

Porous materials, especially metal-organic frameworks, covalent organic frameworks, and supramolecular organic frameworks, are widely used in heterogeneous catalysis, adsorption, and ion exchange. Cucurbit[n]urils (Q[n]s) suitable building units for porous materials because they possess cavities with neutral electrostatic potential, portal carbonyls with negative electrostatic potential, and outer surfaces with positive electrostatic potential, which may result in the formation of Q[n]-based supramolecular frameworks (QSFs) assembled through the interaction of guests within Q[n]s, the coordination of Q[n]s with metal ions, and outer-surface interaction of Q[n]s (OSIQ). This review summarizes the various QSFs assembled via OSIQs. The QSFs can be classified as being assembled by 1) self-induced OSIQ, 2) anion-induced OSIQ, and 3) aromatic-induced OSIQ. The design and construction of QSFs with novel structures and specific functional properties may establish a new research direction in Q[n] chemistry.

Numerical Study on the Characteristics of Boger Type Viscoelastic Fluid Flow in a Micro Cross-Slot under Sinusoidal Stimulation.

The cross-slot geometry plays an important role in the study of nonlinear effects of viscoelastic fluids. The flow of viscoelastic fluid in a micro cross-slot with a high channel aspect ratio (AR, the ratio of channel depth to width) can be divided into three types, which are symmetric flow, steady-state asymmetric flow and time-dependent flow under the inlet condition with a constant velocity. However, the flow pattern of a viscoelastic fluid in the cross-slot when a stimulation is applied at inlets has been rarely reported. In this paper, the response of cross-slot flow under an external sinusoidal stimulation is studied by numerical simulations of a two-dimensional model representing the geometry with a maximum limit of AR. For the cases under constant inlet velocity conditions, three different flow patterns occur successively with the increase of Weissenberg number (Wi). For the cases under sinusoidal varying inlet velocity conditions, when the stimulation frequency is far away from the natural frequency of a viscoelastic fluid, the frequency spectrum of velocity fluctuation field shows the characteristics of a fundamental frequency and several harmonics. However, the harmonic frequency disappears when the stimulation frequency is close to the natural frequency of the viscoelastic fluid. Besides, the flow pattern shows spatial symmetry and changes with time. In conclusion, the external stimulation has an effect on the flow pattern of viscoelastic fluid in the 2D micro cross-slot channel, and a resonance occurs when the stimulation frequency is close to the natural frequency of the fluid.