•Three new terpenoids were isolated from Trigonostemon howii.•The structures were elucidated by NMR data and ECD calculations.•Compounds 2 and 3 possess a rare 3,4-seco-cleistanthane diterpenoid skeleton.•All of the compounds showed NO inhibitory effects.•Molecular docking revealed strong interactions of bioactive compounds with the iNOS protein.A phytochemical investigation to obtain new NO inhibitors led to the isolation of nine compounds including one new guaiane-type sesquiterpenoid (1) and two new cleistanthane diterpenoids (2 and 3) from the stems of Trigonostemon howii. Their structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analysis, and the absolute configurations of new compounds 1–3 were established via comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Compounds 2 and 3 possess a rare 3,4-seco-cleistanthane diterpenoid skeleton. All of the compounds showed inhibitory effects on lipopolysaccharide-induced NO production in murine microglial BV-2 cells. The further molecular docking studies indicated the strong interactions between some bioactive compounds with the iNOS protein, which revealed the possible and potential mechanism of NO inhibition of bioactive compounds.Download high-res image (124KB)Download full-size image

•Four new daphnane diterpenoid orthoesters were isolated from Trigonostemon thyrsoideus.•The structures were elucidated by NMR data and ECD calculations.•Compound 4 features a rare and complex macroring diterpenoid structure.•All of the compounds showed anti-inflammatory effects.•Molecular docking revealed strong affinities of bioactive compounds with iNOS.The extensive pathology studies revealed that Alzheimer’s disease (AD) is closely related to neuroinflammation and anti-neuroinflammatory agents may be potentially useful for the treatment of AD. A continuous search for new nitric oxide (NO) inhibitory compounds as anti-neuroinflammatory agents for AD resulted in the isolation of four new (1−4) and eight known (5−12) daphnane diterpenoids from the twigs of Trigonostemon thyrsoideus. Their structures were elucidated on the basis of extensive nuclear magnetic resonance (NMR) spectroscopic data analysis and the time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. Compounds 1–4 represent new examples of daphnane diterpenoid orthoesters and 4 features a rare and complex macroring diterpenoid structure. The anti-neuroinflammatory effects were examined by inhibiting NO release in lipopolysaccharide (LPS)-induced murine microglial BV-2 cells. The possible mechanism of NO inhibition of some bioactive compounds was also investigated using molecular docking, which revealed the interactions of bioactive compounds with the inducible nitric oxide synthase (iNOS) protein.Download high-res image (141KB)Download full-size image

•Four new phloroglucinols were isolated from Hypericum longistylum.•The structures were elucidated by NMR data and ECD calculations.•Compounds 1–4 possess a rare polycyclic phloroglucinol skeleton.•All of the compounds showed PTP1B inhibitory effects.•Molecular docking revealed strong interactions of bioactive compounds with PTP1B.Protein tyrosine phosphatase 1B (PTP1B) has been regarded as a target for the research and development of new drugs to treat type II diabetes and PTP1B inhibitors are potential lead compounds for this type of new drugs. A phytochemical investigation to obtain new PTP1B inhibitors resulted in the isolation of four new phloroglucinols, longistyliones A–D (1–4) from the aerial parts of Hypericum longistylum. The structures of 1–4 were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analysis, and the absolute configurations of these compounds were established by comparing their experimental electronic circular dichroism (ECD) spectra with those calculated by the time-dependent density functional theory method. Compounds 1–4 possess a rare polycyclic phloroglucinol skeleton. The following biological evaluation revealed that all of the compounds showed PTP1B inhibitory effects. The further molecular docking studies indicated the strong interactions between these bioactive compounds with the PTP1B protein, which revealed the possible mechanism of PTP1B inhibition of bioactive compounds. All of the results implied that these compounds are potentially useful for the treatment of type II diabetes.Download high-res image (251KB)Download full-size image

•Thirteen compounds were isolated from the stems of Melicope pteleifolia.•Their structures were elucidated by analysis of NMR and MS spectroscopic data.•Four compounds are new chroman derivatives.•Eleven compounds showed promoting effects on neurite outgrowth of PC12 cells.Bioactive substances that promote neurite outgrowth and prevent neuronal degeneration are potentially useful for the medical treatment of Alzheimer's disease (AD). This study aimed to obtain bioactive compounds from the stems of the medicinal and edible plant Melicope pteleifolia that promote neurite outgrowth. A bioassay-guided phytochemical investigation led to the isolation of four new chroman derivatives, pteleifolones A–D (1–4), and nine known components, acronyculatin B (5), acronylin (6), marmesin (7), 5-methoxymarmesin (8), (+)-peucedanol (9), atanine (10), N-methylatanine (11), dictamnine (12), and evolitrine (13). Their structures were established by extensive nuclear magnetic resonance (NMR) spectroscopic data analysis. Most of these compounds promoted nerve growth factor (NGF)-mediated neurite outgrowth in PC12 cells. These chemical and biological results provide a basis for the further development and utilization of M. pteleifolia as a functional food.

•Nineteen sesquiterpenoids were isolated and characterized from Petasites japonicus.•The absolute configurations of new compounds were determined by ECD calculations.•Compound 1 contains a chlorine atom and 2 possesses an unusual carbon skeleton.•Fourteen compounds showed promoting effects on neurite outgrowth from PC12 cells.Petasites japonicus (Sieb. & Zucc.) Maxim., belonging to the Compositae family, is a perennial herb and has been consumed as a wild vegetable. Our survey on the chemical composition of P. japonicus resulted in the isolation of two new and seventeen known sesquiterpenoids. Their structures were elucidated on the basis of nuclear magnetic resonance (NMR) spectroscopic data analysis, and the absolute configurations of the new compounds were established by comparison of the calculated and experimental electronic circular dichroism (ECD) spectra. Among these isolates, compound 1 was a sesquiterpene carrying a chlorine atom, 2 processed a rare 7,9-secobakkenolide skeleton, and compounds 4, 11–13, 15, 18, and 19 were obtained from this species for the first time. Most of these compounds showed promoting effects on neurite outgrowth from PC12 cells. These chemical and biological results provide a basis for further development and utilization of P. japonicus as a functional food.

A phytochemical investigation to obtain new NO inhibitors resulted in the identification of six new (1–6) and four known (7–10) terpenoids from Salvia plebeia. Compounds 1 and 2 are new diterpenoids, 3–5 are new meroditerpenoids, 6–9 are sesquiterpenoids, and 10 is a known meroditerpenoid. The structures of these isolates were determined by routine NMR experiments and X-ray diffraction, as well as the electronic circular dichroism spectra. Compounds 1–4 are diterpenoids carrying an oxygen bridge, and 6 is a rare copane-type sesquiterpenoid with a bridged tricyclic framework. The isolates inhibited NO generation induced by lipopolysaccharide in BV-2 cells. The possible mechanism of NO inhibition of some bioactive compounds was also investigated using molecular docking, which revealed interactions of bioactive compounds with the iNOS protein.

A bioassay-guided phytochemical investigation of the leaves of Casearia balansae led to the isolation of six new cucurbitane-type triterpenoid derivatives (balanterpenes A–F, 1–6) and four new clerdoane-type diterpenoids (balanterpenes G–J, 7–10). The structures of 1–10 were established on the basis of extensive analysis of NMR spectroscopic data, X-ray crystallography, and experimental and calculated electronic circular dichroism spectra. Compound 1 features a ring-expanded triterpenoid skeleton with the C-19 methyl involved in the ring formation, compound 6 possesses a rare hexanortriterpenoid scaffold, and compounds 7–10 may be four new diterpenoid artifacts presumably formed during the extraction and purification processes. Compounds 3 and 7–10 showed promoting effects on neurite outgrowth of PC12 cells with EC50 values in the range 2.9–10.0 μM.

A phytochemical investigation to obtain new NO inhibitors led to the isolation of two new (1 and 2) and four known (3–6) diterpenoids from Trigonostemon chinensis. Their structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analyses, and the absolute configurations of new compounds were established by experimental and calculated ECD spectra. The inhibitory activities on lipopolysaccharide-induced NO production in murine microglial BV-2 cells of these diterpenoids were evaluated, and all of the compounds showed inhibitory effects. The interactions of bioactive compounds with iNOS protein were also studied by molecular docking.

Two new ent-pimarane (1 and 2), eight new ent-abietane (3–10) diterpenoids, and eight known analogues (11–18) were isolated from the whole plants of Chloranthus henryi. The absolute configuration of 1 was determined on the basis of single-crystal X-ray diffraction data. Compound 8 represents a class of rare naturally occurring C-14 norabietanes, and compounds 9 and 10 feature rare 13,14-seco-abietane skeletons. Compounds 5, 12, 13, and 15 inhibited the yeast-to-hyphae transition of Candida albicans with IC50 values between 97.3 and 738.7 μM.

Biologically active substances that promote the neurite outgrowth of nerve cells against neuron degeneration may be useful for the treatment of Alzheimer’s disease. In a continuing search for bioactive compounds from plants, an ethyl acetate-soluble extract of the twigs of Casearia graveolens showed moderate stimulatory activity of neurite outgrowth from PC12 cells. Further investigation to obtain bioactive compounds led to the isolation of 10 new clerodane diterpenoids, graveopenes A–J (1–10). Their structures including absolute configurations were elucidated based on analysis of their NMR spectroscopic data and experimental and calculated ECD spectra. Compounds 3–6 and 8 were shown to stimulate NGF-mediated neurite outgrowth from PC12 cells.

Inula japonica belongs to the family Asteraceae, and its flowers have been used as dietary supplements and health tea in China. The study aimed to identify the bioactive components with the antiproliferative property. Ten 1,10-seco-eudesmanolide derivatives, including four new compounds (1–4), were isolated from the flowers of I. japonica. Their structures were established on the basis of the interpretation of spectroscopic data and electronic circular dichroism (ECD) calculations. All of these isolates were evaluated for their antiproliferative activities against MCF-7 and MDA-MB-231 human breast cancer cells. Compound 4 possessed the most potent effects, with the IC50 values of 0.20 ± 0.04 and 6.22 ± 1.30 μM against MCF-7 and MDA-MB-231 cells, respectively. The present investigation indicated that eudesmanolide derivatives from the flowers of I. japonica, especially compound 4, might be used as potential antitumor chemotherapy agent candidates.

Curcuma longa L., belonging to the Zingiberaceae family, is a perennial herb and has been used as a spice and a pigment in the food industry. In the ongoing search for inhibitory reagents of NO production and survey of the chemical composition of natural vegetable foods, the chemical constituents of C. longa used as spice were investigated. This investigation resulted in the isolation of 2 new terpenoids and 14 known analogues. Their structures were established on the basis of the extensive analyses of 1D and 2D NMR spectroscopic data, and the absolute configurations of 1–4 were elucidated by comparison of the calculated and experimental ECD spectra. Among them, compound 1 is a rare norditerpene with an ent-labdane skeleton, and 2 is a skeletally novel sesquiterpene having an eight-membered ring. All of the compounds were found to possess NO inhibitory activities in murine microglial BV-2 cells. The discovery of two new compounds in this chemical investigation further disclosed the chemical composition of C. longa used a food spice, and the bioassay implied that the natural food spice C. longa, containing terpenoids with NO inhibitory activities, may be potentially promotive to human health.

Euphorbia prolifera is a poisonous plant belonging to the Euphorbiaceae family. In this survey on plant secondary metabolites to obtain bioactive substances for the development of new antifungal agents for agriculture, the chemical constituents of the plant E. prolifera were investigated. This procedure led to the isolation of six new and two known diterpenes. Their structures, including absolute configurations, were elucidated on the basis of extensive NMR spectroscopic data analyses and time-dependent density functional theory ECD calculations. Biological screenings revealed that these diterpenes possessed antifungal activities against three phytopathogenic fungi. The results of the phytochemical investigation further revealed the chemical components of the poisonous plant E. prolifera, and biological screenings implied the extract or bioactive diterpenes from this plant may be regarded as candidate agents of antifungal agrochemicals for crop protection products.

Eight new clerodane diterpenes, balanspenes A–H (1–8), along with two known analogues (9 and 10), were isolated from the twigs of Casearia balansae. The structures of 1–8 were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analysis, and the absolute configurations of compounds 1, 4, and 7 were confirmed by comparing their experimental CD spectra with those calculated by the time-dependent density functional theory method. Compounds 4–7, 9, and 10 were found to possess the property of being able to stimulate NGF-mediated neurite outgrowth from PC12 cells.

The inhibitory reagents to inhibit the activation of microglial cells may be potentially useful for the treatment of neurodegenerative diseases. The leaves of the plant Laurus nobilis belonging to the family Lauraceae, namely, bay leaves, have been used as a popular spice, and their extract showed moderate inhibition on microglial activation. A further phytochemical investigation of the leaves led to the isolation of two new (1, 2) and eight known (3–10) sesquiterpenes. Their structures were elucidated on the basis of extensive 1D and 2D NMR (HMQC, HMBC, 1H–1H COSY, and NOESY) spectroscopic data analyses and Chem3D modeling. The following biological studies disclosed that these isolated compounds showed inhibitory activities on LPS-induced microglial activation. The results of our phytochemical investigation, including two new sesquiterpenes (1 and 2) and the first report of two compounds (3 and 4) from this species, further revealed the chemical composition of bay leaves as a popular spice, and the biological studies implied that bay leaves, containing bioactive substances with the inhibition of microglial activation, were potentially beneficial to human health.

Petasites tatewakianus is an edible plant belonging to the family Compositae. In our continuous search for NO inhibitors, which may be useful for the development of anti-inflammatory agents, the chemical constituents of the leaves of the edible plant P. tatewakianus were investigated. This phytochemical investigation led to the isolation of 3 new (1–3) and 10 known (4–13) sesquiterpenes and 2 other types of known compounds (14 and 15). Their structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analyses, and the absolute configurations of compounds 1 and 3 were confirmed by comparing their experimental CD spectra with those calculated by the time-dependent density functional theory (TDDFT) method. The following biological studies disclosed that these isolated compounds showed inhibitory activities on LPS-induced NO production in murine microglial BV-2 cells. The results of our phytochemical investigation, including two new bakkenolide sesquiterpenes (1 and 2), one new sesquiterpene with an unusual carbon skeleton (3), and the first report of compounds 5–7 and 10–15 from this species, further revealed the chemical composition of P. tatewakianus as an edible plant, and the biological studies implied that P. tatewakianus, containing bioactive substances with the inhibitory activities of NO production, was potentially beneficial to human health.

•Petasites japonicus has been consumed as a vegetable and used as a medicine.•Eight new and two known sesquiterpenes have been isolated and characterised.•The neuroprotective activities of these sesquiterpenes were evaluated.•Five compounds showed a neuroprotective activity.Neuroprotective reagents to protect the nerve cells against oxidative stress and other damages are potentially effective for the medical treatment of Parkinson’s disease. Petasites japonicus, a wild vegetable, belongs to the family Compositae and its extract has shown the neuroprotective effects. A further phytochemical investigation of P. japonicus for neuroprotective substances led to the isolation of eight new (1–8) and two known (9 and 10) sesquiterpenes. Their structures were elucidated on the basis of extensive 1D and 2D NMR (HMQC, HMBC, 1H–1H COSY, and NOESY) spectroscopic data analyses, and the structure of 1 was confirmed by X-ray crystallography. The neuroprotective activities of these sesquiterpenes were evaluated against cobalt chloride (CoCl2)-induced neuronal cell death in human dopaminergic SH-SY5Y cells. Five compounds showed a neuroprotective activity.

Blumea balsamifera belongs to the family Compositae, and its leaves have been used as a flavoring ingredient and a tea. A phytochemical investigation of the aerial parts of B. balsamifera led to the isolation of 10 new (1–10) and 1 known (11) sesquiterpenes. Their structures were elucidated on the basis of extensive one- and two-dimensional nuclear magnetic resonance (heteronuclear multiple-quantum coherence, heteronuclear multiple-bond correlation, 1H–1H correlation spectroscopy, and nuclear Overhauser effect spectrometry) spectroscopic data analyses, and the structure of compound 1 was confirmed by X-ray crystallography. The inhibitory activities on lipopolysaccharide-induced NO production in murine microglial BV-2 cells of these sesquiterpenes were evaluated, and all of the compounds showed inhibitory effects.

Ten new neo-clerodane diterpenes, ajugaciliatins A–J (1–5, 8–12), along with 17 known analogues (6, 7, 13–27) were isolated from the whole plants of Ajuga ciliata Bunge. Their structures were elucidated by spectroscopic data analysis (IR, ESIMS, HRESIMS, 1D and 2D NMR), and the configuration of 1 was confirmed by X-ray crystallography. All of the compounds were assessed for neuroprotective effects against MPP+-induced neuronal cell death in dopaminergic neuroblastoma SH-SY5Y cells. Compounds 2, 6, 7, 9, 10, 15–17, 19, and 20 exhibited moderate neuroprotective effects.

Ten myrsinol diterpenes, euphorbiaproliferins A–J (1–10), along with nine known analogues (11–19) were isolated from the roots of Euphorbia prolifera. Their structures were elucidated by spectroscopic data analysis (IR, ESIMS, HRESIMS, 1D and 2D NMR), and the structure of 1 was confirmed by X-ray crystallography. The diterpenes showed neuroprotective effects against MPP+-induced neuronal cell death in SH-SY5Y cells.

A new heterocyclic compound, named 5,5′-diisobutoxy-2,2′-bifuran (1), and four known compounds (2–5) were isolated from the roots of Cyathula officinalis Kuan. Their structures were elucidated by spectroscopic methods. Among these compounds, 5,5′-dibutoxy-2,2′-bifuran (2) was isolated for the first time from this plant.

Caesalpinia decapetala is a versatile medicinal plant belonging to the Fabaceae plant family. In our survey on plant secondary metabolites to obtain bioactive substances for the development of new agricultural anti-TMV agents, the chemical constituents of C. decapetala were investigated. This investigation led to the isolation of three new and ten known diterpenoids. Their structures including absolute configurations were elucidated based on the extensive NMR spectroscopic data analyses and the time-dependent density functional theory calculations. The following biological screenings revealed that most of these diterpenoids possessed anti-TMV activities.Download high-res image (262KB)Download full-size image

•Four new and ten known compounds were isolated from Tussilago farfara.•Their structures were elucidated by NMR spectroscopic data analyses.•Compound 1 is a new sesquiterpene carrying a chlorine atom.•All of the isolates showed NO inhibitory effects.•Bioactive compounds showed strong binding with iNOS protein.Tussilago farfara L. is a well-known herb plant and used widely in China, North Africa, and Europe. A phytochemical investigation to obtain new NO inhibitors resulted in the isolation of three new sesquiterpenes, one new phenolic derivative, and ten known compounds from the flower buds of T. farfara. Their structures were established on the basis of extensive analyses of nuclear magnetic resonance (NMR) spectroscopic data. All of the isolates exhibited inhibitory effects on LPS-induced NO production in BV-2 cells. The possible mechanism of NO inhibition was also investigated using molecular docking, which revealed the interactions of bioactive compounds with iNOS protein. The present study disclosed that flower buds of T. farfara have the potential to be developed into a functional food.

A phytochemical investigation to obtain new NO inhibitors resulted in the isolation of a new diterpenoid with a rare 9,10-seco-abietane skeleton (1) and twelve known terpenoids (2–13) from Callicarpa kwangtungensis. Their structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analyses, and the absolute configuration of compound 1 was established by comparison of the calculated and experimental electronic circular dichroism (ECD) spectra. The inhibitory activities on lipopolysaccharide-induced NO production in murine microglial BV-2 cells of these terpenoids were evaluated, and all of the compounds showed inhibitory effects. The following molecular docking studies showed interactions of the bioactive compounds with the iNOS protein.

A phytochemical investigation of the leaves of Callicarpa macrophylla led to the isolation of five new diterpenoids (1–5), macrophypenes A–E, and nine known analogues (6–14). The structures of 1–5 were established on the basis of extensive analysis of NMR spectroscopic data, X-ray diffraction data, and experimental and calculated electronic circular dichroism spectra. Compound 1 is a spiroditerpenoid with a novel skeleton, and compound 5 is a rare ent-abietane diterpenoid possessing a peroxide bridge. Compounds 1, 5–7, and 11–14 stimulate nerve growth factor mediated neurite outgrowth from PC12 cells.