Bioactive sesquiterpenoids from the flower buds of Tussilago farfara

Natural products with potential hypoglycemic activity in T2DM: 2019-2023

As currently the most common metabolic disease, type 2 diabetes mellitus (T2DM) has shown a continuous increase in the number of patients in recent decades. Most anti-T2DM drugs tend to cause some side effects. Given the pathogenesis of T2DM, natural products have emerged as an important source of anti-T2DM drugs. This article reviews natural products with potential hypoglycemic activity from 2019 to 2023. A total of 200 previously natural products were discovered on SciFinder, PubMed and Web of Science. These products were categorized based on their structural frameworks and their biological activities were summarized. Although the mechanisms of action of most compounds are unclear, these compounds could still serve as candidates for the development of lead compounds. Therefore, further structure and activity research of natural products will significantly contribute to the development of potential anti-T2DM drugs.

Bioassay-guided discovery and identification of new potent α-glucosidase inhibitors from Morus alba L. and the interaction mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

Morus alba L. (mulberry) is a well-known medicinal species that has been used by herbalist doctors for the treatment of diabetes for a long history, and modern ethnopharmacological studies have demonstrated the ameliorating effects of different mulberry extracts toward diabetes-related symptoms and identified a number of α-glucosidase inhibitors as hypoglycemic ingredients.

AIM OF THE STUDY

The present study aims to explore new potent α-glucosidase inhibitors from the root bark of M. alba (known as Sang-Bai-Pi in traditional medicine) based on an in vivo antidiabetic evaluation of its extract fractions and further characterize the preliminary mechanism of the new active constituents.

MATERIALS AND METHODS

α-Glucosidase inhibitory assay and diabetic mice model were used to locate and evaluate the active fractions from the extract. Diverse separation techniques (e.g. Sephadex LH-20 column chromatograph (CC) and HPLC) and spectroscopic methods (e.g. MS, NMR and ECD) were employed to isolate and structurally characterize the obtained constituents, respectively. Fluorescence quenching, kinetics and molecular docking experiments were conducted to investigate the enzyme inhibitory mechanism of the active compounds.

RESULTS

The 80% ethanol eluate from the macroporous resin CC exerted good antidiabetic effects in the tested mice. Fifty-two flavonoids including 22 new ones were then separated and identified, and most of them showed strong inhibition against α-glucosidase with their structure-activity relationship being also discussed. The four new most active ingredients were further characterized to be mixed type of α-glucosidase inhibitors, and their binding modes with the enzyme were also explored.

CONCLUSIONS

Our current work has demonstrated that the root bark of M. alba is an extremely rich source of flavonoids as potent α-glucosidase inhibitors and potential antidiabetic agents, which makes it a promising candidate species to develop new natural remedies for the prevention and treatment of diabetes.

Inonotsutriol E from Inonotus obliquus exhibits promising anti breast cancer activity via regulating the JAK2/STAT3 signaling pathway

The aim of the present study was to investigate the small molecule anticancer agents in the medicinal fungus Inonotus obliquus and further characterize their possible molecular mechanisms. Chemical fractionation of the ethanol extract of this fungus yielded a panel of lanostane triterpenoids (1-13) and their structures were characterized on the basis of spectroscopic methods. Subsequent preliminary biological screening on these triterpenoids revealed significant cytotoxicity against various tumor cell lines, and inonotsutriol E (ITE, 1) showed the best activity. Of note, ITE displayed stronger inhibitory effect on breast cancer (BC) than other tumor cell lines. Functional assays revealed that ITE significantly inhibited the growth and migration of BC cells and exerted promising antitumor activity in patient-derived organoids (PDO). Further mechanistic study demonstrated that the anti-BC activity of ITE was achieved via inhibiting JAK2/STAT3 signal axis. Taken together, the current work has demonstrated the therapeutic material basis of I. obliquus and provided further evidence for the traditional application of this medicinal species in cancer prevention and treatment.

Rare diphenylheptanoid-phenylheptanoid hybrids with α-glucosidase inhibitory effects from the pollen of Typha angustifolia

Two rarely occurring diphenylheptanoid-phenylheptanoid hybrid dimers (1 and 2) and one new oxygenated fatty acid (3), as well as two known fatty acid analogues (4 and 5), were isolated from the 70% EtOH extract of the pollen of Typha angustifolia. Their planar structures were established by interpretation of MS and NMR spectroscopic data, and the absolute configurations of 1 and 2 were determined by Mosher's method and quantum chemical TD-DFT calculations of ECD spectra. An in vitro anti-diabetic evaluation of these isolates revealed that compounds 1 and 2 exhibited promising inhibitory activity against α-glucosidase with IC50 values of 11.85 ± 0.69 and 17.06 ± 3.08 μM, respectively. It is the first report on both diphenylheptanoid constituents and α-glucosidase inhibitors from the title plant, which represents a significant phytochemical progress of this herbal species and may serve as a reference for its future medicinal applications.

New di-spirocyclic labdane diterpenoids from the aerial parts of Leonurus japonicus

Phytochemical investigation on the ethanol extract of a well-known medicinal herb Leonurus japonicus, led to the separation of 18 labdane type diterpenoids (1-18). Through comprehensive spectroscopic analyses and quantum chemical calculations, these compounds were structurally characterized as six new interesting 5,5,5-di-spirocyclic ones (1-6), two new (7 and 8) and six known (13-18) interesting 6,5,5-di-spirocyclic ones, a new rare 14,15-dinor derivative (9), and three new ones incorporating a γ-lactone unit (10-12). An in vitro neuroprotective assay in RSC96 cells revealed that compounds 7 and 12 exhibited neuroprotective activity in a concentration-dependent way, comparable to the reference drug N-acetylcysteine.

Isolation and identification of Tussilago farfara leaf spot caused by Alternaria alternata in China

Tussilago farfara is of vital medical value. A new leaf spot disease was observed on T. farfara leaves, in Dingxi, Gansu Province, China, in October 2019. In order to research the pathogen, the diseased samples were collected for isolation and identification. The isolate KD3 was verified by pathogenicity test, as the pathogen causing the T. farfara leaf spot disease. Its morphological characteristics were consistent with Alternaria alternata, the colony color gray-green with concentric rings, conidia fusiform and pear-shaped, brown, with 1-7 septa and 0-3 longitudinal septa, conidia size (19. 62-44.49) μm × (6.97-10.53) μm, beak length (1.35-10.03) μm × (1.01-3.63) μm, and the spore phenotype was a dwarf tree-like chain of short conidia. Multilocus sequences analysis manifested that the internal transcribed spacer (ITS), Alternaria major allergen (Alta1), and Calcium barine (CAL) sequences of strain KD3 were most closely to A. alternata (A23), with the homology of 99.47%, 99.56% and 98.28%, respectively. Based on morphological and molecular characteristics, strain KD3 was identified as A. alternata. OA was the optimal medium for its growth and PCA medium was the optimal for sporulation. This is the first report of A. alternata causing T. farfara leaf spots in China.

Clerodane furanoditerpenoids from the stems of Tinospora sinensis

One new clerodane-type furanoditerpenoid tinosinoid A (1) and nine new nor-clerodane analogs tinosinoids B-J (2-10) have been isolated from the stems of Tinospora sinensis. The structures of the new compounds with absolute configurations have been elucidated by spectroscopic means, including MS, NMR and ECD techniques, as well as chemical correlation. Compound 1 is a rare sulfur-containing clerodane diterpenoid incorporating a 2-mercaptoethanol unit via a thioether bond, while compounds 4/5 and 9 represent two pairs of unusual equilibrium regioisomers through an interesting intramolecular transesterification. Our bioassays established that 1 and 8 displayed moderate antiproliferative effects against two human tumor cell lines, and 9 and 10 showed significant α-glucosidase inhibitory activities. A kinetics study revealed that compound 10 was a noncompetitive α-glucosidase inhibitor, and its possible binding mode to the enzyme was further probed by molecular docking experiments.

The Complexity of Sesquiterpene Chemistry Dictates Its Pleiotropic Biologic Effects on Inflammation

Sesquiterpenes (SQs) are volatile compounds made by plants, insects, and marine organisms. SQ have a large range of biological properties and are potent inhibitors and modulators of inflammation, targeting specific components of the nuclear factor-kappaB (NF-κB) signaling pathway and nitric oxide (NO) generation. Because SQs can be isolated from over 1600 genera and 2500 species grown worldwide, they are an attractive source of phytochemical therapeutics. The chemical structure and biosynthesis of SQs is complex, and the SQ scaffold represents extraordinary structural variety consisting of both acyclic and cyclic (mono, bi, tri, and tetracyclic) compounds. These structures can be decorated with a diverse range of functional groups and substituents, generating many stereospecific configurations. In this review, the effect of SQs on inflammation will be discussed in the context of their complex chemistry. Because inflammation is a multifactorial process, we focus on specific aspects of inflammation: the inhibition of NF-kB signaling, disruption of NO production and modulation of dendritic cells, mast cells, and monocytes. Although the molecular targets of SQs are varied, we discuss how these pathways may mediate the effects of SQs on inflammation.

Chemistry and Bioactivity of Marine-Derived Bisabolane Sesquiterpenoids: A Review

Natural products, characterized by intriguing scaffold diversity and structural complexity, as well as significant agricultural and medicinal activities, have been a valuable source of agrochemicals/drugs development and have historically made a huge contribution to pharmacotherapy. Structurally, bisabolanes are a family of naturally occurring sesquiterpenoids that featured a hexatomic ring core incorporating with eight continuous carbons, which cause high structural variability along the alkyl side chain to form abundant functionalities. Moreover, apart from their interesting structures, bisabolanes have shown multitudinous bioactivities. Bisabolanes are distributed in a variety of marine invertebrates, terrestrial plant, and microbial sources. Interestingly, bisabolanes characterized from marine environment possess unique characteristics both structurally and biologically. A total of 296 newly-discovered bisabolanes were searched. Among them, 94 members were isolated from marine organisms. This review particularly focuses on the new bisabolanes characterized from marine organisms (covering from 2000 to 2021), including marine-derived fungi, algae, soft corals, and sponges, with emphasis on the diversity of their chemical structures as well as the novelty and differences between terrestrial and marine sources. Moreover, a wide range of bioactivities of marine-derived bisabolanes, including antimicrobial, anti-inflammatory, enzyme inhibitory, and cytotoxic properties, are presented herein, which is considered to be a promising resource for the discovery of new drug leads and agrochemicals.

The complete chloroplast genome sequence of Tussilago farfara (Asteraceae)

Tussilago farfara is a member of the family Asteraceae. In this paper, we reported the complete chloroplast (cp) genome sequence of T. farfara. The results showed that T. farfara complete chloroplast genome comprises 151,325 bp, containing a largen single copy (LSC) region of 83,370 bp, a small single copy (SSC) region of 18,273 bp, and a pair of inverted repeats (IRs) region of 24,841 bp. The genome has a GC content of 37.4%. The LSC, SSC, and IR regions represent 35.5%, 30.6%, and 43.0% of the T. farfara chloroplast genome length. We annotated 132 genes, comprising 87 protein-coding genes (PCGs), eight rRNA genes, and 36 tRNA genes. A phylogenetic analysis based on 31 cpDNA genomes suggested that the T. farfara is closely related to Farfugium japonicum.

Novel Quinic Acid Glycerates from Tussilago farfara Inhibit Polypeptide GalNAc-Transferase

The discovery of a bioactive inhibitor tool for human polypeptide N-acetylgalactosaminyl transferases (GalNAc-Ts), the initiating enzyme for mucin-type O-glycosylation, remains challenging. In the present study, we identified an array of quinic acid derivatives, including four new glycerates (1-4) from Tussilago farfara, a traditional Chinese medicinal plant, as active inhibitors of GalNAc-T2 using a combined screening approach with a cell-based T2-specific sensor and purified enzyme assay. These inhibitors dose-dependently inhibited human GalNAc-T2 but did not affect O-linked N-acetylglucosamine transferase (OGT), the other type of glycosyltransferase. Importantly, they are not cytotoxic and retain inhibitory activity in cells lacking elongated O-glycans, which are eliminated by the CRISPR/Cas9 gene editing tool. A structure-activity relationship study unveiled a novel quinic acid-caffeic acid conjugate pharmacophore that directs inhibition. Overall, these new natural product inhibitors could serve as a basis for developing an inhibitor tool for GalNAc-T2.

Diterpenoid glucosides with cystathionine γ-lyase inhibitory activity from Tinospora sinensis

Fifteen previously undescribed nor-clerodane diterpenoid glucosides tinosinesides C-Q (1-15), along with four known analogues (16-19), were isolated from the stems of Tinospora sinensis. The structures of the new compounds were elucidated by spectroscopic means, and their absolute configurations were established on the basis of time-dependent density functional theory (TD-DFT) based electronic circular dichroism (ECD) calculation and chemical methods. All the isolates were evaluated for their inhibitory effects on cystathionine γ-lyase (CSE), a natural enzyme responsible for the synthesis of H₂S. Compounds 4 and 5 represent rare examples of natural CSE inhibitors and the possible binding mode to CSE was further probed by molecular docking experiment.