Uncarialins J—M from Uncaria rhynchophylla and Their Anti‐depression Mechanism in Unpredictable Chronic Mild Stress‐Induced Mice via Activating 5‐HT 1A Receptor

The beneficial pharmacological effects of Uncaria rhynchophylla in neurodegenerative diseases: focus on alkaloids

With the intensification of aging population, the prevention or treatment of neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease, has drawn more and more attention. As a long used traditional Chinese medicine, Uncaria rhynchophylla (Miq.) Jacks., named Gouteng in Chinese, has been reported to have an effective neuroprotective role in neurodegenerative diseases. In this review, the beneficial pharmacological effects and signaling pathways of herbal formulas containing U. rhynchophylla, especially major compounds identified from U. rhynchophylla, such as corynoxine B, corynoxine, rhynchophylline, and isorhynchophylline, in neurodegenerative diseases, were summarized, which not only provide an overview of U. rhynchophylla for the prevention or treatment of neurodegenerative diseases but also give some perspective to the development of new drugs from traditional Chinese medicine.

Potential Mechanisms of Casein Hexapeptide YPVEPF on Stress-Induced Anxiety and Insomnia Mice and Its Molecular Effects and Key Active Structure

The hexapeptide YPVEPF with strong sleep-enhancing effects could be detected in rat brain after a single oral administration as we previously proved. In this study, the mechanism and molecular effects of YPVEPF in the targeted stress-induced anxiety mice were first investigated, and its key active structure was further explored. The results showed that YPVEPF could significantly prolong sleep duration and improve the anxiety indexes, including prolonging the time spent in the open arms and in the center. Meanwhile, YPVEPF showed strong sleep-enhancing effects by significantly increasing the level of the GABA/Glu ratio, 5-HT, and dopamine in brain and serum and regulating the anabolism of multiple targets, but the effects could be blocked by bicuculline and WAY100135. Moreover, the molecular simulation results showed that YPVEPF could stably bind to the vital GABAA and 5-HT1A receptors due to the vital structure of Tyr-Pro-Xaa-Xaa-Pro-, and the electrostatic and van der Waals energy played dominant roles in stabilizing the conformation. Therefore, YPVEPF displayed sleep-enhancing and anxiolytic effects by regulating the GABA-Glu metabolic pathway and serotoninergic system depending on distinctive self-folding structures with Tyr and two Pro repeats.

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

Discovery and Biomimetic Semisynthesis of Spirophyllines A-D from Uncaria rhynchophylla

Spirophyllines A-D (1-4), four new spirooxindole alkaloids all characterized by the spiro[pyrrolidin-3,3'-oxindole] core and a rare isoxazolidine ring, were isolated from Uncaria rhynchophylla. Their structures were determined by spectroscopic methods and confirmed by X-ray crystallography. Based on the biomimetic semisynthesis strategy, compounds 1-8 were synthesized in three steps via the key reactions of 1,3-dipolar cycloaddition and Krapcho decarboxylation from corynoxeine. Interestingly, compound 3 showed moderate inhibitory activity against the Kv1.5 potassium channel (IC50 = 9.1 μM).

Uncarialines A-E, new alkaloids from Uncaria rhynchophylla and their anticoagulant activity

Uncarialines A-E (1-5), five undescribed monoterpene indole alkaloids, together with five known analogues were obtained from the stems of Uncaria rhynchophylla. Alkaloids 1-3 were unique 3,4-seco-tricyclic alkaloids with a 6/5/10 ring system, while 4 and 5 possessed a rare rearranged scaffold originated from corynantheine-type alkaloids with C-2/C-7 oxidation. Their structures were characterized by a comprehensive analysis of MS, NMR, and ECD. Their effects on blood clotting times of human plasma were evaluated and alkaloid 5 had a slight prolongation effect on both thrombin time and activated partial thromboplastin time (p < 0.001).

Minor monoterpene derivatives from an aqueous extract of the hook-bearing stem of Uncaria rhynchophylla

Seven new minor monoterpene derivatives (1-7), together with six known analogues, were isolated from an aqueous decoction of the hook-bearing stems of Uncaria rhynchophylla (Gou-teng). Their structures were determined by spectroscopic data analysis and electronic circular dichroism (ECD) calculations, of which 1 was confirmed by single crystal X-ray diffraction.

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 (K_i) 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.