Leonuketal, a Spiroketal Diterpenoid fromLeonurus japonicus

Five new bisabolane-type sesquiterpenoids with oxygen-containing heterocyclic systems from Curcuma longa

Five new bisabolane-type sesquiterpenoids (1-5) were isolated from the rhizomes of Curcuma longa, and all of them were oxygen-containing heterocyclic compounds. The structures of the compounds were elucidated using comprehensive spectroscopic techniques, and their absolute configurations were confirmed through electronic circular dichroism (ECD) calculations. All of the compounds were evaluated for their vasorelaxant and anti-inflammatory activities. The results showed that only compound 4 exhibited a vasorelaxant effect against KCl-induced contraction of rat aortic rings, and it achieved a diastolic ratio that exceeded 25 % at a concentration of 25 μM.

Ethnobotanical study of medicinal plants used by the Yi people in Mile, Yunnan, China

BACKGROUND

The Yi people are a sociolinguistic group living in Mile City, which is their typical settlement in southeastern Yunnan, China. Over the long history of using medicinal plants, the Yi people have accumulated and developed a wealth of traditional medicinal knowledge, which has played a vital role in their health care. However, only a few studies have been performed to systematically document the medicinal plants commonly used by the Yi people. This study provides fundamental data for the development and application of ethnomedicine as well as supports the conservation of the traditional medical knowledge of the Yi people.

METHODS

This study was conducted from May 2020 to August 2022 and involved five townships in Mile. Information regarding medicinal plants was obtained through semistructured interviews, key informant interviews, and participatory observation. The collected voucher specimens were identified using the botanical taxonomy method and deposited in the herbarium. Ethnobotanical data were analyzed using informant consensus factor, relative frequency of citation, and fidelity level.

RESULTS

In total, 114 informants distributed in five townships of Mile were interviewed. The Yi people used 267 medicinal plant species belonging to 232 genera and 104 families to treat various diseases. Asteraceae, Lamiaceae, and Fabaceae were the most commonly used plant families by the Yi people. In addition, herbs were most commonly used by the Yi people. Whole plants and roots were the preferred medicinal parts. Decoctions were the most common method of herbal medicine preparation. There are 49 different recorded diseases treated by Yi medicinal plants, and among them, respiratory diseases, rheumatism, traumatic injury, fractures, and digestive system diseases have the largest number of species used. A quantitative analysis demonstrated that plants such as Zingiber officinale, Lycopodium japonicum, Aconitum carmichaelii, Panax notoginseng, Cyathula officinalis, and Leonurus japonicus played crucial roles in disease prevention and treatment.

CONCLUSION

Traditional knowledge of medicinal plants is closely associated with the social culture of the local Yi people. The medicinal plants used for health care in the study area were diverse. Local healers were skilled at using medicinal plants to treat various diseases. Their treatment methods were convenient and unique, exhibiting distinctive regional characteristics. However, the inheritance of their traditional medicinal knowledge and protection of wild medicinal plant resources are facing serious challenges, including the decreasing number of local healers, aging of healers, lack of successors, and excessive harvesting of medicinal plant resources. This ethnobotanical survey provides a useful reference for the sustainable utilization and protection of medicinal plant resources in Mile and the inheritance of traditional medicinal knowledge of the Yi people.

Nectar Characteristics and Honey Production Potential of Five Rapeseed Cultivars and Two Wildflower Species in South Korea

The growing beekeeping industry in South Korea has led to the establishment of new honey plant complexes. However, studies on honey production from each species are limited. This study aimed to assess the honey production potential of various Brassica napus cultivars and two wildflower species. The nectar characteristics of B. napus varied significantly among the cultivars. Absolute sugar concentrations differed among the cultivars, but sugar composition ratios were similar. In contrast, the amino acid content remained relatively uniform regarding percentage values, irrespective of the absolute concentrations. Estimations of honey potential production per hectare (kg/ha) resulted in the following ranking among cultivars: 'JM7003' (107.1) > 'YS' (73.0) > 'JM7001' (63.7) > 'TL' (52.7) > 'TM' (42.4). The nectar volume of Pseudolysimachion rotundum var. subintegrum and Leonurus japonicus increased during the flowering stage. P. rotundum var. subintegrum was sucrose-rich and L. japonicus was sucrose-dominant. Both species predominantly contained phenylalanine, P. rotundum var. subintegrum had glutamine as the second most abundant amino acid, and L. japonicus had tyrosine. The honey production potential was 152.4 kg/ha for P. rotundum var. subintegrum and 151.3 kg/ha for L. japonicus. These findings provide a basis for identifying food resources for pollinators and selecting plant species to establish honey plant complexes.

De novo chromosome-level genome assembly of Chinese motherwort (Leonurus japonicus)

Chinese motherwort (Leonurus japonicus), a member of Lamiaceae family, is a commonly used medicinal herb for treating obstetrical and gynecological diseases, producing over 280 officinal natural products. Due to limited genomic resources, little progress has been made in deciphering the biosynthetic pathway of valuable natural products in L. japonicus. Here, we de novo assembled the L. japonicus genome using high-coverage ONT long reads and Hi-C reads. The chromosome-level genome assembly contained ten chromosomes representing 99.29% of 489.34 Mb genomic sequence with a contig and scaffold N50 of 7.27 Mb and 50.86 Mb, respectively. Genome validations revealed BUSCO and LAI score of 99.2% and 21.99, respectively, suggesting high quality of genome assembly. Using transcriptomic data from various tissues, 22,531 protein-coding genes were annotated. Phylogenomic analysis of 13 angiosperm plants suggested L. japonicus had 58 expanded gene families functionally enriched in specialized metabolism such as diterpenoid biosynthesis. The genome assembly, annotation, and sequencing data provide resources for the elucidation of biosynthetic pathways behind natural products of pharmaceutical applications in L. japonicus.

Total Synthesis of Terpenes and Their Biological Significance: A Critical Review

Terpenes are a group of natural products made up of molecules with the formula (C5H8)n that are typically found in plants. They are widely employed in the medicinal, flavor, and fragrance industries. The total synthesis of terpenes as well as their origin and biological potential are discussed in this review.

Curcumanes E and F, two rare sesquiterpenoids with a dicyclo[3.3.1]nonane moiety, from Curcuma longa and their vasorelaxant activities

Two new sesquiterpenoids, curcumanes E (1) and F (2), were isolated from the rhizome of Curcuma longa, and their structures and absolute configurations were examined using extensive spectroscopic analyses and ECD calculations. Interestingly, compounds 1 and 2 are diastereoisomers possessing a rare sesquiterpenoid skeleton that has been reported only once before. Both curcumanes E and F exhibit significant vasorelaxant effects against KCl-induced contraction of rat aortic rings, with EC50 values of 5.10 ± 0.79 and 5.58 ± 1.77 μM, respectively. These findings enrich the data concerning this rare type of sesquiterpenoids and further indicate that these rare sesquiterpenoids can effectively reduce blood pressure.

Vasorelaxant effect of curcubisabolanin A isolated from Curcuma longa through the PI3K/Akt/eNOS signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Curcuma longa L. (Zingiberaceae) is a known blood-activating and stasis-removing traditional Chinese medicine and has relevant pharmacological properties. The rhizomes of C. longa have been used for the treatment of cardiovascular disease (CVD) in China. Previous studies have shown that sesquiterpenoids from C. longa have significant vasorelaxant effects, which are closely associated with the prevention and treatment of CVD.

AIM OF THE STUDY

To explore the sesquiterpenoids with vasorelaxant effects from C. longa and investigate the underlying mechanisms.

MATERIALS AND METHODS

The compound was isolated from C. longa by multiple chromatography technologies. Its structure was determined by extensive spectroscopic analyses, nuclear magnetic resonance (NMR) data calculations, electronic circular dichroism (ECD) data calculations, and optical rotation (OR) data calculations. The vasorelaxant effect of the isolated compound was evaluated by KCl- or phenylephrine (PHE)-inducing contraction of the rat thoracic aortic rings. Endothelial removal and L-NAME pretreatment experiments were used to verify the endothelium-dependent vasorelaxant effect of the isolated compound in rat thoracic aortic rings. NO production was monitored in human umbilical vein endothelial cells (HUVECs). Western blot was carried out in HUVECs to elucidate the potential mechanisms.

RESULTS

A new bisabolane-type sesquiterpenoid, curcubisabolanin A [(+)-(1S,7S,9E)-bisabola-2(3),4(15),9(10)-trien-11-ol], was isolated from the rhizomes of C. longa. curcubisabolanin A exhibited endothelium-dependent relaxation on rat thoracic aortic rings, while pre-treatment of intact aortic rings with an eNOS inhibitor (L-NAME) attenuated the vasorelaxant response of curcubisabolanin A. In addition, curcubisabolanin A induced intracellular NO production and significantly increased the levels of phosphorylated PI3K (p-PI3K), phosphorylated Akt (p-Akt), and phosphorylated eNOS (p-eNOS) in HUVECs. LY294002 (a blocker of PI3K) and MK-2206 (a highly selective inhibitor of Akt) significantly decreased these effects of curcubisabolanin A.

CONCLUSIONS

These findings demonstrated that the vasorelaxant effect of curcubisabolanin A was partially endothelium-dependent and was related to regulation of NO production in vascular endothelial cells through the PI3K/Akt/eNOS signaling pathway.

New lignans from the fruits of Leonurus japonicus and their hepatoprotective activities

Twelve tetrahydrofuran lignans (1-12), including six new compounds (1-6), were isolated from the 70% EtOH extract of the fruits of Leonurus japonicus. Spectroscopic analyses and ECD and OR calculations were used to determine their structures. Compounds 5 and 6 were unusual alkaloidal lignans with a butyrolactam unit. Based on the beneficial effects of the fruits of L. japonicus (Chongweizi in Chinese) on the liver in traditional Chinese medicine (TCM), the hepatocyte protective activities of the isolates were studied by MTT, Hoechst 33,342 staining, and western blotting. The MTT results revealed that compounds 1, 2, 7, and 8 significantly increased the survival rates of HL-7702 cells injured by acetaminophen, with EC₅₀ values of 10.41 ± 0.90 μM, 19.86 ± 3.13 μM, 9.68 ± 1.93 μM, and 21.35 ± 3.58 μM, respectively. In the Hoechst 33,342 fluorescence staining, compounds 1 and 7 suppressed the apoptosis of the injured HL-7702 cells. Furthermore, the western blot analysis showed that compounds 1 and 7 increased the Bcl-2/Bax protein expression ratio and procaspase-3 protein expression, indicating that compounds 1 and 7 may exert hepatoprotective activity by regulating the mitochondrial apoptotic pathway.

Leonurine Ameliorates Oxidative Stress and Insufficient Angiogenesis by Regulating the PI3K/Akt-eNOS Signaling Pathway in H2O2-Induced HUVECs

Thrombus is considered to be the pathological source of morbidity and mortality of cardiovascular disease and thrombotic complications, while oxidative stress is regarded as an important factor in vascular endothelial injury and thrombus formation. Therefore, antioxidative stress and maintaining the normal function of vascular endothelial cells are greatly significant in regulating vascular tension and maintaining a nonthrombotic environment. Leonurine (LEO) is a unique alkaloid isolated from Leonurus japonicus Houtt (a traditional Chinese medicine (TCM)), which has shown a good effect on promoting blood circulation and removing blood stasis. In this study, we explored the protective effect and action mechanism of LEO on human umbilical vein endothelial cells (HUVECs) after damage by hydrogen peroxide (H₂O₂). The protective effects of LEO on H₂O₂-induced HUVECs were determined by measuring the cell viability, cell migration, tube formation, and oxidative biomarkers. The underlying mechanism of antioxidation of LEO was investigated by RT-qPCR and western blotting. Our results showed that LEO treatment promoted cell viability; remarkably downregulated the intracellular generation of reactive oxygen species (ROS), malondialdehyde (MDA) production, and lactate dehydrogenase (LDH); and upregulated the nitric oxide (NO) and superoxide dismutase (SOD) activity in H₂O₂-induced HUVECs. At the same time, LEO treatment significantly promoted the phosphorylation level of angiogenic protein PI3K, Akt, and eNOS and the expression level of survival factor Bcl2 and decreased the expression level of death factor Bax and caspase3. In conclusion, our findings suggested that LEO can ameliorate the oxidative stress damage and insufficient angiogenesis of HUVECs induced by H₂O₂ through activating the PI3K/Akt-eNOS signaling pathway.

seco-Labdanes: A Study of Terpenoid Structural Diversity Resulting from Biosynthetic C-C Bond Cleavage

The cleavage of a C-C bond is a complexity generating process, which complements oxidation and cyclisation events in the biosynthesis of terpenoids. This process leads to increased structural diversity in a cluster of related secondary metabolites by modification of the parent carbocyclic core. In this review, we highlight the diversifying effect of C-C bond cleavage by examining the literature related to seco-labdanes-a class of diterpenoids arising from such C-C bond cleavage events.

Total Synthesis of (±)-Leonuketal

Leonuketal is an 8,9-seco-labdane terpenoid with a unique tetracyclic structure, owing to a diversity-generating biosynthetic C-C bond cleavage event. The first total synthesis of leonuketal is reported, featuring a Ti(III)-mediated reductive cyclization of an epoxy nitrile ether, an unusual ring-opening alkyne formation as part of an auxiliary ring strategy, and the previously undescribed Au(I)-catalyzed cyclization of a β-keto(enol)lactone to assemble the core spiroketal motif.

Structurally Diverse Labdane Diterpenoids from Leonurus japonicus and Their Anti-inflammatory Properties in LPS-Induced RAW264.7 Cells

A phytochemical study on the aerial parts of Leonurus japonicus led to the isolation and identification of 38 labdane diterpenoids, including 18 new (1, 2, 11, 12, 16-21, 24, 30-34, 37, 38) and 20 known (3-10, 13-15, 22, 23, 25-29, 35, 36) analogues. Their structures were elucidated based on physical data analysis, including 1D and 2D NMR, HRMS, UV, IR, and X-ray diffraction. The structure of the known compound 4 was confirmed by single-crystal X-ray diffraction data. These compounds can be divided into furanolabdane (1-10), tetrahydrofuranolabdane (11-15), lactonelabdane (16-23), labdane (24-29), and seco-labdane (30-38) type diterpenoids. All compounds were screened by lipopolysaccharide (LPS)-induced nitric acid (NO) production in RAW264.7 cells to evaluate anti-inflammatory effects. Compounds 1, 5, 10-13, 16-19, 31-33, and 38 inhibited NO production with IC₅₀ values lower than 50 μM, with compound 30 being the most active, with an IC₅₀ value of 3.9 ± 1.7 μM. Further studies show that compound 30 inhibits pro-inflammatory cytokine production and IKK α/β phosphorylation and restores the IκB expression levels in the NF-κB signaling pathway.

Halimane and labdane diterpenoids from Leonurus japonicus and their anti-inflammatory activity

Ten highly oxygenated diterpenoids (nine undescribed ones) were isolated from the aerial parts of Leonurus japonicus Houtt. 14,15-Dinor-labd-5,8-dien-3,13-dione was a 14,15-dinor-labdane diterpenoid possessing a C₁₈ skeleton. 7β,9α-Dihydroxy-6-oxo-labd-13-en-15,16-amide represented a rare example of labdane diterpenoid featuring an α,β-unsaturated-γ-lactam moiety. The structures of all compounds were elucidated using spectroscopic data analyses and comparisons. The effects of these obtained compounds on nitric oxide (NO) production induced by lipopolysaccharide (LPS) in RAW 264.7 cells were evaluated.(10R*,13R*,15R*)-15,16-Epoxy-6,13-dihydroxy-15-methoxy-labda-5,8-dien-7-one inhibited NO production with an IC₅₀ value of 40.1 μM.

Asymmetric Synthesis of [2.2.2]-Bicyclic Lactones via All-Carbon Inverse-Electron-Demand Diels-Alder Reaction

In this paper, a new cycloaddition between α,β-unsaturated aldehydes and coumalates realized under dienamine activation has been described. The reaction proceeds regioselectively with the distal double bond of the dienamine system acting as electron-rich dienophile. It leads to the formation of biologically relevant [2.2.2]-bicyclic lactones. Their functionalization potential has been confirmed in selected, diastereoselective transformations.

Curcumane C and (±)-curcumane D, an unusual seco-cadinane sesquiterpenoid and a pair of unusual nor-bisabolane enantiomers with significant vasorelaxant activity from Curcuma longa

A new seco-cadinane sesquiterpenoid (curcumane C, 1) and a pair of new nor-bisabolene enantiomers [(+)- and (-)-curcumane D, 2a and 2b] were isolated from C. longa. Compound 1 possesses an unusual 4,5-seco-cadinane skeleton with a tetrahydrophthalide moiety, while 2a and 2b contain an unusual 15-nor-bisabolene skeleton with a chromone core. All compounds exhibited significant vasorelaxant effects against KCl-induced contraction of rat aortic rings. Compound 1 also exhibited a vasorelaxant effect against phenylephrine-induced contraction of rat aortic rings. Meanwhile, compound 1 showed a stronger vasorelaxant effect in endothelium-intact rat aortic rings compared with endothelium-denuded rat aortic rings, indicating that vasodilation by 1 involved both endothelium-dependent and endothelium-independent pathways. Furthermore, compound 1 increased the NO content in human umbilical vein endothelial cells and its vasorelaxant effect could be attenuated by treatment with L-NAME, an endothelium NO synthase inhibitor. Thus, the underlying vasodilatory mechanisms of 1 may be mediated via abrogation of extracellular Ca²⁺ influx and regulation of NO release in vascular endothelial cells.

Comparative analysis of the main active constituents from different parts of Leonurus japonicus Houtt. and from different regions in China by ultra-high performance liquid chromatography with triple quadrupole tandem mass spectrometry

A rapid, sensitive and convenient analytical method of ultra-performance liquid chromatography coupled with triple-quadrupole linear ion-trap tandem mass spectrometry (UPLC-QTRAP®/MS²) was proposed for the simultaneous determination of characteristic alkaline and acidic components covering many structure types including alkaloids, phenolic acids, phenylpropanoids and flavonoids in Leonurus japonicus Houtt. (LJ). The proposed method was first reported and validated by assessing the matrix effects, linearity, limit of detections, limit of quantifications, precision, repeatability, stability and recovery of target components. The developed UPLC-QTRAP®/MS² was successfully applied to simultaneously determine all target compounds in 38 batches of LJ from 11 different producing regions in China and five organs (including root, caulis, branch, flower and leaf) of LJ from the same stand planting base in Jiangsu Province (China). The result showed that LJ in different regions with different geographical position would affect the accumulation of different compounds, and the significant discrepancies of some target compounds were also observed in different organs of LJ due to different biosynthetic pathway and enzymes in different organs. Furthermore, both hierarchical clustering analysis and principal components analysis were performed to classify the 38 batches of LJ samples from different producing regions on the basis of target compounds. As a result, the samples could be mainly clustered into different groups, which were similar with areas classification. Overall, the presented method would be helpful for the comprehensive utilization and development of LJ resources.

A new labdane-type diterpenoid from Leonurus japonicus

Five fractions prepared from the crude extract of Leonurus japonicus were examined in order to determine their cytotoxic potential. Under the bioassay guidance, a new labdane-type diterpenoid (1), and nine known ones (2-10) along with a seco-labdane (11) were isolated from the aerial parts of Leonurus japonicus. The structure elucidation was primarily based on comprehensive spectroscopic analyses, including HRESIMS, IR, and 1D and 2D NMR methods. Compound 4 (6β-hydroxy-15,16-epoxylabda-8,13(16),14-trien-7-one) exhibited potential cytotoxicity against HeLa cell line (IC₅₀ = 23.75 μM).

Absolute Configurations and Bioactivities of Guaiane-Type Sesquiterpenoids Isolated from Pogostemon cablin

Seven novel guaiane sesquiterpenoids (1-7) and three known seco-guaianes were isolated from the volatile oil of Pogostemon cablin. Their structures including absolute configurations were determined by spectroscopic analyses, a modified Mosher's method, and X-ray diffraction and ECD data. The results indicated that the ECD Cotton effects arising from one or two nonconjugated olefinic chromophores could be applied to define the absolute configurations of guaiane sesquiterpenoids. Compounds 3 and 6 exhibited significant vasorelaxant activity against phenylephrine-induced and KCl-induced contractions of rat aorta rings [half-maximal effective concentration (EC₅₀) of 3 against PHE-induced contraction, 5.4 μM; EC₅₀ of 6 against PHE- and KCl-induced contractions, 1.6 and 24.2 μM, respectively]. They also showed antifungal activity against Candida albicans (minimum inhibitory concentrations, 500 and 300 μM, respectively). In addition, 2 and 7-9 displayed a neuroprotective effect against glutamate-induced injury in PC12 cells.

Synthesis of the Bicyclic Lactone Core of Leonuketal, Enabled by a Telescoped Diels-Alder Reaction Sequence

The Diels-Alder cycloaddition reaction has become established as a fundamental approach for the preparation of complex natural products; however, successful application of the intermolecular Diels-Alder cycloaddition reaction to the synthesis of particularly congested scaffolds remains surprisingly problematic. Inspired by the terpenoid spiroketal natural product leonuketal, a challenging telescoped reaction sequence has been realized to access the core [2.2.2]-bicyclic lactone ring system and its [3.2.1] isomer. Our four-step, protecting-group-free process required detailed investigation to circumvent the problems of adduct fragmentation and intermediate instability. Successful solution of these practical issues, along with unambiguous structural determination of the target structures, provide useful insights that will facilitate future applications of the Diels-Alder cycloaddition reaction to challenging, highly congested molecular scaffolds and ongoing synthetic efforts towards this natural product.

Natural Products Research in China From 2015 to 2016

This review covers the literature published by chemists from China during the 2015-2016 on natural products (NPs), with 1,985 citations referring to 6,944 new compounds isolated from marine or terrestrial microorganisms, plants, and animals. The emphasis is on 730 new compounds with a novel skeleton or/and significant bioactivity, together with their source organism and country of origin.

Discovery of Leonuri and therapeutical applications: From bench to bedside

Despite several advances in percutaneous coronary intervention and the discovery of new drugs, the incidence of myocardial infarction and deaths due to cardiovascular diseases (CVD) has not decreased markedly in China. The quality of life is affected seriously, which further results in great social and family burden. Many drugs, from the century-old aspirin to the newly FDA-approved Byvalson, have been proven to be effective in the treatment and prevention of CVD. As clinically reported, those life-saving drugs still have their side effects in regards to the narrow therapeutic indexes influenced by individual genetic variations. Herba Leonuri, also known as Chinese Motherwort, which are naturally present in plants and traditionally are used for the uterotonic action, postpartum blood stasis, breast pain as well as other gynecological disorders in China for thousands of years. Since the last two decades, our group has reported leonurine, a unique alkaloid found in Herba Leonuri, exhibits various bioactivities such as antioxidant, anti-apoptotic effects, free radical scavenging and anti-inflammatory effects, in addition to improving micro-circulation. These bioactivities are related to the underlying mechanisms of ischemic heart diseases and cardiac fibrosis. Pharmacological studies have proven leonurine to be effective in treating CVD in various ways, particularly ischemic heart diseases. Besides the cardio protective effects, which are similar in the central nervous system, more specifically, inhibited mitochondrial reactive oxygen species production together with the restored mitochondrial function and redox state were observed in middle cerebral artery occlusion rats by leonurine treatment, which strongly reveals its neuroprotective effects and carries a therapeutic potential for recovery and prevention of stroke. Based on their mode of action, we propose that leonurine can be developed as drugs to treat ischemic heart diseases. Taking advantage of the most recent findings in pharmacological research including the effects of low toxicity and good pharmacokinetics characteristics, leonurine has a very attractive prospect of clinical application. Our recent promising pharmacological results may be able to eradicate the barrier hindering its sale on market. In sum, from bench to bedside is no longer a long way for leonurine.

Phytochemistry and pharmacology of the genus Leonurus: The herb to benefit the mothers and more

Plants belonging to the genus Leonurus, also named motherwort, are traditionally used for anti-gynecological disorder in East Asia, and for sedative in Europe. Chemical investigation of the genus Leonurus not only enriched the natural products library, but also enlarged the pharmacological application of this traditional herb. In this review, we systematically summarized the structures of 259 compounds isolated from the genus Leonurus, featured with 147 labdane diterpenoids. The reported bioactivity studies up to 2017 are presented in the second part, with the main focus on the isolated compounds and also concerning the extracts. In addition to the traditional uterine contraction and sedative activity, recently the cardiovascular protection effect of leonurine has drawn most attention. Other than that, neuroprotection, anti-inflammation, anti-cancer, anti-platelet aggregation and many other activities have been assigned to various compounds from the genus Leonurus. Among 70 bioactivity references cited in this review, 57% of them were concentrated on two alkaloids (leonurine and stachydrine), whereas only 20% are about the 147 diterpenoids. Anti-inflammation is the major bioactivity discovered so far for the labdane diterpenoids from the genus Leonurus, whose further therapeutic potential still remains for exploration.

New diterpenoids isolated from Leonurus japonicus and their acetylcholinesterase inhibitory activity

Three new labdane diterpenoids, leojaponicone A (1), isoleojaponicone A (2) and methylisoleojaponicone A (3), were isolated from the herb of Leonurus japonicus. The chemical structures of these secondary metabolites were elucidated on the basis of 1D and 2D NMR, including HMQC, and HMBC spectroscopic techniques. All the new compounds were tested in vitro for their acetylcholinesterase and α-glucosidase inhibitory activity. Compounds 1-3 exhibited low inhibitory effects on α-glucosidase with respect to acarbose and exhibited high inhibitory effects on acetylcholinesterase with respect to huperzine A.

A Tri-O-Bridged Diels-Alder Adduct from Cortex Mori Radicis

Sanggenon X, an unusual tri-O-bridged Diels-Alder adduct, was isolated from Cortex Mori Radicis. Its structure was established by spectroscopic analysis, including NMR and HR-MS (High Resolution Mass Spectrometry). Sanggenon X contained three O-bridged rings, where the oxygenated bridgeheads were all quaternary carbons. Chemical methylation was carried out to deduce the linkages of the three O-bridges. The absolute configuration was determined by calculating the ECD (Electronic Circular Dichroism) using the TDDFT (Time-Dependent Density Functional Theory) method. Sanggenon X showed significant antioxidant activity against Fe²⁺-Cys-induced lipid peroxidation in rat liver microsomes, and was as effective as the positive control, curcumin.

Recent progress in the isolation, bioactivity, biosynthesis, and total synthesis of natural spiroketals

The isolation, bioactivity, biosynthesis, and total synthesis of natural spiroketals from 2011 to July 2017 have been summarized in this review.

Alkaloids and flavonoid glycosides from the aerial parts of Leonurus japonicus and their opposite effects on uterine smooth muscle

The crude extract and some Chinese patented medicines of Leonurus japonicus Houtt. have been proven to affect the uterine smooth muscle. L. japonicus injection is widely used in obstetric departments in China for treating postpartum hemorrhage caused by uterine inertia. Bioassay-guided isolation of the 95% EtOH extract of L. japonicus yielded four cyclopeptides, nine alkaloids, and three flavonoid glycosides, including two previously undescribed cyclopeptides, namely, cycloleonuripeptide G and cycloleonuripeptide H. The structures of the cyclopeptides were elucidated to be cyclo-(L-Phe-L-Phe-Gly-L-Pro-Gly-L-Pro) and cyclo-(L-Phe-L-Ala-L-Pro-L-Ile-L-His-Gly-L-Ala-L-Pro), respectively, via spectroscopic and chemical methods. Cyclopeptides (cycloleonuripeptides C and D) and alkaloids (imperialine-3β-D-glucoside and leonurine) promoted contraction of uterine smooth muscle strips isolated from normal rats. However, it was observed that flavonoid glycosides (spinosin, linarin, and apigenin-7-O-β-D-glucopyranoside) significantly inhibited contraction of the uterine smooth muscle strips.

Pocahemiketals A and B, two new hemiketals with unprecedented sesquiterpenoid skeletons from Pogostemon cablin

Pocahemiketals A and B (1 and 2), two novel hemiketal sesquiterpenoids with unprecedented skeletons, were isolated from the essential oil of the aerial parts of Pogostemon cablin. In addition to a bicyclo[3.2.1]-carbon core, 1 and 2 possessed a hemiketal α,β-unsaturated-γ-lactone moiety. Their structures were determined by extensive spectroscopic analysis, electronic circular dichroism calculation, and single-crystal X-ray diffraction. Compound 2 exhibited significant vasorelaxant activity against phenylephrine-induced contraction of a rat aorta ring with the EC₅₀ value of 16.32μM.

Hot off the press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as guajavadimer A 7 from leaves of Psidium guajava.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes labdanes, clerodanes, pimaranes, abietanes, kauranes, cembranes and their cyclization products. The literature from January to December, 2015 is reviewed.