Muurolane sesquiterpenes from illicium tsangii

Cadinane sesquiterpenes from the stems and branches of Illicium ternstroemioides

Three new cadinane sesquiterpenes (1-3) and three known sesquiterpenes were isolated from the stems and branches of Illicium ternstroemioides A. C. Smith. The structures of the new compounds were elucidated by extensive analysis of spectroscopic and HRESIMS data. The structures of illiternins A-C (1-3) were confirmed by single crystal X-ray diffraction, allowing for the determination of their absolute configurations. Compounds 3 and 6 exhibited antiviral activity against Coxsackievirus B3 with IC50 values of 33.3 and 57.7 μM, respectively.

Bergamotane-type sesquiterpenes from the leaves and twigs of Illicium oligandrum and their anti-inflammatory activities

Eight undescribed β-bergamotene-type sesquiterpene oliganins A-H (1-8) and one known α-bergamotene-type sesquiterpene (9) were isolated from the leaves and twigs of Illicium oligandrum Merr. & Chun. The structures of compounds 1-8 were elucidated by extensive spectroscopic data, and the absolute configurations were determined by using a modified Mosher's method and electronic circular dichroism calculations. The isolates were further evaluated in terms of their anti-inflammatory potential on nitric oxide (NO) generation in lipopolysaccharide-stimulated RAW264.7 and BV2 cells. Compounds 2 and 8 exhibited potent inhibitory effects on the production of NO with IC₅₀ values ranging from 21.65 to 49.28 μM, which were greater than or comparable to those of dexamethasone (positive control).

seco-Sesquiterpenes and acorane-type sesquiterpenes with antiviral activity from the twigs and leaves of Illicium henryi Diels

Chemical investigation of an alcohol extract from the twigs and leaves of Illicium henryi Diels resulted in the isolation of two new acorane-related seco-sesquiterpenes (1 and 3), two new acorane-related seco-norsesquiterpenes (2 and 4), one new 2-epi-cedrane sesquiterpene (5), eight new acorane-type sesquiterpenes (6-13), and a known major constituent of acorenone B (14). Their structures were established by interpreting extensive spectroscopic data, including HRESIMS, NMR (¹H and ¹³C NMR, ¹H-¹H COSY, HSQC, and HMBC), and NOE difference spectra analysis. The absolute configurations of 1, 2, 4-7, 9, 10, and 14 were determined by X-ray crystallography, while chemical transformation methods were performed with compound 14 as the starting material to elegantly solve the absolute configuration issue of compounds 8 and 11-13. Notably, 1 and 2 are seco-sesquiterpenes that are related to acorane and possess an unusual ketal-linked hemiacetal in a 6,8-dioxabicyclo[3.2.1]octan-7-ol scaffold ring system. Plausible biosynthetic pathways for compounds 1-14, which were derived from the acorane skeleton, were proposed. All the isolated compounds (1-14) were evaluated for their antiviral and cytotoxic activities.

Anti-inflammatory aromadendrane- and cadinane-type sesquiterpenoids from the South China Sea sponge Acanthella cavernosa

One new aromadendrane-type sesquiterpenoid, namely ximaocavernosin P [(+)-1], and three new cadinane-type sesquiterpenoids, namely (+)-maninsigin D [(+)-4], (+)- and (−)-ximaocavernosin Q [(+)- and (−)-5], together with five related known ones [2, 3, (−)-4, 6, and 7], were isolated from the Hainan sponge Acanthella cavernosa. Compounds 4 and 5 were isolated as racemic forms, which were further separated to the corresponding enantiomers [(+)-4/(−)-4 and (+)-5/(−)-5], respectively, by using chiral-phase HPLC. The structures of new compounds were elucidated by extensive spectroscopic analysis and comparison with the reported data. In addition, the absolute configuration of optically pure (+)-1 and 2 were determined by time-dependent density functional theory/electronic circular dichroism (TDDFT-ECD) calculations or X-ray diffraction analysis. A plausible biosynthetic pathway of these sesquiterpenoids and their internal correlation were proposed and discussed. In an in vitro bioassay, (+)-aristolone (3) exhibited promising anti-inflammatory activity by the inhibition of LPS-induced TNF-α and CCL2 release in RAW 264.7 macrophages.

Antiprotozoal and Antitumor Activity of Natural Polycyclic Endoperoxides: Origin, Structures and Biological Activity

Polycyclic endoperoxides are rare natural metabolites found and isolated in plants, fungi, and marine invertebrates. The purpose of this review is a comparative analysis of the pharmacological potential of these natural products. According to PASS (Prediction of Activity Spectra for Substances) estimates, they are more likely to exhibit antiprotozoal and antitumor properties. Some of them are now widely used in clinical medicine. All polycyclic endoperoxides presented in this article demonstrate antiprotozoal activity and can be divided into three groups. The third group includes endoperoxides, which show weak antiprotozoal activity with a reliability of up to 70%, and this group includes only 1.1% of metabolites. The second group includes the largest number of endoperoxides, which are 65% and show average antiprotozoal activity with a confidence level of 70 to 90%. Lastly, the third group includes endoperoxides, which are 33.9% and show strong antiprotozoal activity with a confidence level of 90 to 99.6%. Interestingly, artemisinin and its analogs show strong antiprotozoal activity with 79 to 99.6% confidence against obligate intracellular parasites which belong to the genera Plasmodium, Toxoplasma, Leishmania, and Coccidia. In addition to antiprotozoal activities, polycyclic endoperoxides show antitumor activity in the proportion: 4.6% show weak activity with a reliability of up to 70%, 65.6% show an average activity with a reliability of 70 to 90%, and 29.8% show strong activity with a reliability of 90 to 98.3%. It should also be noted that some polycyclic endoperoxides, in addition to antiprotozoal and antitumor properties, show other strong activities with a confidence level of 90 to 97%. These include antifungal activity against the genera Aspergillus, Candida, and Cryptococcus, as well as anti-inflammatory activity. This review provides insights on further utilization of polycyclic endoperoxides by medicinal chemists, pharmacologists, and the pharmaceutical industry.

Sesquiterpenoids of diverse types from the rhizomes of Acorus calamus

Six new and fourteen known sesquiterpenoids of diverse types were isolated from the rhizomes of Acorus calamus.

Hydrogen peroxide derived from marine peroxy sesquiterpenoids induces apoptosis in HCT116 human colon cancer cells

In this study, the isolates of the peroxy sesquiterpenoids (1-3) from the Okinawan soft coral, Sinularia sp., indicated cytotoxicity in HCT116 colon cancer cells. The apoptotic cells with a nuclear condensation were detected in the presence of these compounds, then the caspase 3/7 activity was induced, indicating that the compounds have a potential antitumor activity by apoptosis-induction. The cells treated with these compounds were generated reactive oxygen species (ROS), indicating that the ROS is related to the induction of apoptosis. The ROS production reduced in the presence of catalase or trolox, indicating that hydrogen peroxide (H2O2) is generated through a certain free radical reaction derived from the compound. In fact, the accumulation of intracellular H2O2 was also confirmed in the presence of these compounds. Based on all the results, this study proposed the apoptosis-inducing mechanism due to the compounds that the H2O2 produced involving free radical reactions derived from cleavage of the end or hydro-peroxide in the molecule induced cell death.

Endoperoxy and hydroperoxy cadinane-type sesquiterpenoids from an Okinawan soft coral, Sinularia sp

Three cadinane-type sesquiterpenoids, endoperoxide (1) and hydroperoxides (2, 3) together with three known sesquiterpenoids (4-6) were isolated from an Okinawan soft coral, Sinularia species. Structures of these isolates were elucidated by spectroscopic analyses (NMR, IR and MS) and molecular modeling. In addition, the isolates 1-3 as new compounds were examined for biological activities, resulting that they have antibacterial activity and weak cytotoxicity against HCT116 cells as well as anti-inflammatory effect on LPS/IFN-γ-stimulated RAW 264.7 macrophage cells.

Muurolane-type sesquiterpenes from marine sponge Dysidea cinerea

Seven new muurolane-type sesquiterpenes, (4R,5R)-muurol-1(6),10(14)-diene-4,5-diol (1), (4R,5R)-muurol-1(6)-ene-4,5-diol (2), (4R,5R,10R)-10-methoxymuurol-1(6)-ene-4,5-diol (3), (4S)-4-hydroxy-1,10-seco-muurol-5-ene-1,10-dione (4), (4R)-4-hydroxy-1,10-seco-muurol-5-ene-1,10-dione (5), (6S,10S)-6,10-dihydroxy-7,8-seco-2,8-cyclo-muurol-4(5),7(11)-diene-12-oic acid (6), and (6R,10S)-6,10-dihydroxy-7,8-seco-2,8-cyclo-muurol-4(5),7(11)-diene-12-oic acid (7) were isolated from the marine sponge Dysidea cinerea. Their structures were determined by the combination of spectroscopic and chemical methods, including 1D-NMR, 2D-NMR, and CD spectra as well as by comparing the NMR data with those reported in the literature.

Diterpenoids and sesquiterpenoids from the roots of Illicium majus

Five new diterpenoids (1-5), five new sesquiterpenoids (6-10), and three known compounds (11-13) were isolated from the roots of Illicium majus. Their structures were elucidated by extensive spectroscopic analysis. The absolute configuration of 1 was assigned by X-ray crystallography, whereas those of the 1,2-diol moieties in 3 and 4 were determined using Snatzke's method. The abietane acids 1, 2, 11, 12, and 13 displayed antiviral activity against the Coxsackie B3 virus, with IC50 values of 3.3-51.7 μM/mL.

Peroxy natural products

This review covers the structures and biological activities of peroxy natural products from a wide variety of terrestrial fungi, higher plants, and marine organisms. Syntheses that confirm or revise structures or stereochemistries have also been included, and 406 references are cited.

Prenylated C6-C3 compounds from the roots of Illicium henryi

Eleven prenylated C(6)-C(3) compounds, illihenryifunones A, B (1, 2), illihenryifunol A (3), illihenryipyranol A (4), illihenryiones A-G (5-11), and three known prenylated C(6)-C(3) compounds (12-14), were isolated from the roots of Illicium henryi. Structures of 1-11 were elucidated by spectroscopic methods including NMR, HRESIMS, and CD. The absolute configuration of the 11,12-diol moiety in 5 was determined by observing its induced circular dichroism after addition of Mo(2)(OAc)(4) in DMSO. The absolute configuration of C-11 in 4 was determined as S based on the Rh(2)(OCOCF(3))(4)-induced CD data; the absolute configuration of 3 was determined as R by comparison of its experimental and calculated electronic circular dichroism (ECD). The antioxidant activities of compounds 1-14 were also evaluated. Compound 4 exhibited strong antioxidant activity with an IC(50) value of 2.97±1.30 μM, whereas compounds 3 and 8 showed antioxidant activities with IC(50) values of 44.36±0.30 and 48.00±2.01 μM, respectively.

Prenylated C6-C3 compounds with molecular diversity from the roots of Illicium oligandrum

Eleven prenylated C(6)-C(3) compounds, illioliganpyranone A (1), illioliganfunone A-D (2-5), and illioliganone D-I (6-11), together with five known prenylated C(6)-C(3) compounds (12-16), were isolated from roots of Illicium oligandrum. The structures of 1-11 were elucidated by spectroscopic methods including 1D and 2D NMR, HRESIMS, and CD experiments. Possible biosynthetic pathways to compounds 1-16 derived from a common precursor of 5-allylbenzene-1,2,4-triol were postulated. All compounds were evaluated for cytotoxic activities against five human cancer cell lines (HCT-8, Bel-7402, BGC-823, A549 and A2780). Compound 15 exhibited significant cytotoxicity against HCT-8, BGC-823, A549, and A2780 cell lines with IC(50) values of 0.30-2.57 μM. Compound 16 showed moderate selective cytotoxicity against sensitive A2780 cells with IC(50) value of 1.38 μM.

Rearranged prenylated C6-C3 compounds and a highly oxygenated seco-prezizaane-type sesquiterpene from the stem bark of Illicium oligandrum

Three new rearranged prenylated C(6)-C(3) compounds, named illioliganones A, B, and C (1-3), and a new highly oxygenated seco-prezizaane-type sesquiterpene, oligandriortholactone (7), together with three known prenylated C(6)-C(3) compounds (4-6) and a known sesquiterpene lactone (8), have been isolated from the stem bark of Illicium oligandrum. The structures of 1-3 and 7 were elucidated by spectroscopic methods including 1D and 2D NMR, HRMS, and CD experiments. The absolute configuration of the 11,12-diol moiety in 2 and 3 was determined on the basis of observing the induced circular dichroism after addition of Mo(2)(OAc)(4) in DMSO solution. The anti-inflammatory and cytotoxic activities of 1-8 were evaluated.

Mechanistic and structural requirements for active site labeling of phosphoglycerate mutase by spiroepoxides

We recently reported the pharmacological screening of a natural products-inspired library of spiroepoxide probes, resulting in the discovery of an agent MJE3 that displayed anti-proliferative effects in human breast cancer cells. MJE3 was found to covalently inactivate phosphoglycerate mutase-1 (PGAM1), a glycolytic enzyme with postulated roles in cancer cell metabolism and proliferation. Considering that MJE3 is one of the first examples of a cell-permeable, small-molecule inhibitor for PGAM1, we pursued a detailed examination of its mechanism and structural requirements for covalent inactivation. MJE3 was found to label PGAM1 on lysine-100, a conserved active site residue implicated in substrate recognition. Structural features of MJE3 important for PGAM1 labeling included two key recognition elements (an indole ring and carboxylic acid), the stereochemical orientation of the spiroepoxide, and presentation of these various binding/reactive groups on a rigid cyclohexane scaffold. Modeling studies of the docked MJE3-PGAM1 complex provide a structural rationale for these stringent requirements. Overall, these studies indicate that a special combination of binding and reactive elements are united in the MJE3 structure to inactivate PGAM1. More generally, our findings provide further evidence that useful pharmacological tools can emerge from screening structurally diverse libraries of protein-reactive probes.

High-level production of amorpha-4,11-diene in a two-phase partitioning bioreactor of metabolically engineered Escherichia coli

Reconstructing synthetic metabolic pathways in microbes holds great promise for the production of pharmaceuticals in large-scale fermentations. By recreating biosynthetic pathways in bacteria, complex molecules traditionally harvested from scarce natural resources can be produced in microbial cultures. Here we report on a strain of Escherichia coli containing a heterologous, nine-gene biosynthetic pathway for the production of the terpene amorpha-4,11-diene, a precursor to the anti-malarial drug artemisinin. Previous reports have underestimated the productivity of this strain due to the volatility of amorphadiene. Here we show that amorphadiene evaporates from a fermentor with a half-life of about 50 min. Using a condenser, we take advantage of this volatility by trapping the amorphadiene in the off-gas. Amorphadiene was positively identified using nuclear magnetic resonance spectroscopy and determined to be 89% pure as collected. We captured amorphadiene as it was produced in situ by employing a two-phase partitioning bioreactor with a dodecane organic phase. Using a previously characterized caryophyllene standard to calibrate amorphadiene production and capture, the concentration of amorphadiene produced was determined to be 0.5 g/L of culture medium. A standard of amorphadiene collected from the off-gas showed that the caryophyllene standard overestimated amorphadiene production by approximately 30%.

Sesqui- and diterpenoids from two Japanese and three European liverworts

A new peroxy muurolane-type sesquiterpenoid was isolated from the ether extract of the Belgium liverwort Scapania undulata, together with three known ent-muurolanes. A new lepidozane-type sesquiterpenoid was isolated from the Japanese Porella subobtusa together with a known santalane- and two africane-type sesquiterpenoids. All structures were determined by means of NMR spectroscopic techniques. The chemosystematics of each species are discussed.