Lactarane sesquiterpenoids from Lactarius subvellereus and their cytotoxicity

Subvellerolactones B (1), D (2), and E (3), structurally unusual lactarane sesquiterpenoids, were isolated from the fruiting bodies of Lactarius subvellereus together with four known lactarane sesquiterpenes (4–7). The chemical structures and stereochemistries of compounds 1–3 were determined on the basis of spectroscopic analyses, including 1D and 2D NMR experiments and a convenient Mosher ester procedure. Subvellerolactone B (1) exhibited cytotoxicity against the A549, SK-MEL-2, and HCT-15 cell lines with IC₅₀ values of 26.5, 18.3, and 14.2 μM, respectively, and subvellerolactones D (2) and E (3) showed cytotoxicity against the A549 and HCT-15 cell lines (IC₅₀ (2): 25.1 and 17.8 μM, and IC₅₀ (3): 19.6 and 28.7 μM, respectively).     

Three new benzophenone glycosides with MAO-A inhibitory activity from Hypericum thasium Griseb.

Purification of n-BuOH fraction from 80% ethanol extract of Hypericum thasium Griseb. resulted in the isolation of three new compounds 3′,4,5′-trihydroxy-6-methoxy-2-O-α-l-arabinosylbenzophenone (1), 3′,4,5′,6-tetrahydroxy-2-O-α-l-arabinosylbenzophenone (2), and 3′,4-dihydroxy-5′-methoxy-2-O-α-l-arabinosyl-6-O-β-d-xylosylbenzophenone (3) along with a known flavonoid glycoside quercetin-3-O-α-l-arabinofuranoside (4). The structures of the new compounds were elucidated by 1D and 2D NMR analysis as well as HRESIMS. The isolated compounds (1–4), as well as quercetin, and kaempferol previously isolated from EtOAc fraction were screened against MAO-A inhibitory activity. When tested against the MAO-A quercetin and kaempferol displayed IC₅₀ values of 19.6, and 17.5 μM, respectively. The IC₅₀ values for MAO-A inhibition by compounds (1–4) were 310.3, 111.2, 726.0, and 534.1 μM, respectively. Standard inhibitor (clorgyline) exhibited MAO-A inhibition with an IC₅₀ value of 0.5 μM.     

Two new lignans from Gymnotheca chinensis Decne

Two new lignans, gymnothelignans V (1) and W (2), were isolated from a methanol extraction of Gymnotheca chinensis Decne. Their structures were established on the basis of extensive 1D and 2D NMR spectroscopy. Compound 1 exhibited moderate cytotoxicity against the HCT116, HCT15, A549, MCF-7 and HepG2 cancer cell lines with IC₅₀ values of 45.1 μM, 26.9 μM, 49.6 μM, 30.0 μM and 49.7 μM, respectively. Compound 2 exhibited weak cytotoxicity against the A549 cancer cell line with an IC₅₀ value of 41.3 μM.     

Triterpenes from the roots of Lantana montevidensis with antiprotozoal activity

Bioassay guided fractionation of the roots of Lantana montevidensis (Verbenaceae) has resulted in the isolation and identification of three new triterpenoids; 13β-hydroxy-3-oxo-olean-11-en-28-oic acid (1), 12β,13β-dihydroxyolean-3-oxo-28-oic acid (2) and 12β,13β,22β-trihydroxyolean-3-oxo-28-oic acid (3) in addition to nine known compounds: oleanonic acid (4), oleanolic acid (5), 3β,25β-dihydroxy-olean-12-en-28-oic acid (6), lantadene A (7), 19α-hydroxy-3-oxo-olean-12-en-28-oic acid (8) pomolic acid (9), camaric acid (10) together with β-sitosterol (11) and β-sitosterol-3-O-β-d-glucoside (12). The structures of the isolated metabolites were elucidated based on comprehensive 1D and 2D NMR spectroscopic data as well as HR-ESI–MS. The extracts and the isolated metabolites were evaluated for their antiprotozoal and antimicrobial activities. Compound 2 showed antibacterial activity against Staphylococcus aureus and methicillin resistant S. aureus with IC₅₀ values against both organisms of 2.1 μM and compound 10 showed activity against same organisms with IC₅₀ values 8.74 and 8.09 μM, respectively, compared to the positive control ciprofloxacin (IC₅₀ = 0.3 μM against S. aureus and MRSA). Compounds 1, 4, 5, 6, and 10 showed moderate antileishmanial activity with IC₅₀ values ranging between (2.54–14.95 μM) and IC₉₀ values ranging between (11.90–19.47 μM), using pentamidine as a control (IC₅₀ values 2.09 ≥ 16.8 μM) and IC₉₀ values ranging between (4.72 ≥ 16.8 μM). These compounds also showed highly potent antitrypanosomal activity with IC₅₀ values ranging between (0.39–7.12 μM) and IC₉₀ values ranging between (1.91–10.51 μM), which are more efficient than the DFMO, the antitrypanosomal drug employed as positive control (IC₅₀ and IC₉₀values 11.82 and 30.82 μM).     

A biphenyl derivative from the twigs of Chaenomeles speciosa

In our continuing search for bioactive constituents of Korean medicinal sources, we investigated an 80% MeOH extract of the twigs of Chaenomeles speciosa. Column chromatographic purification of the CHCl₃ fraction resulted in the isolation of a new biphenyl derivative (1), along with four known biphenyl compounds (2–5) and six triterpenes (6–11). The chemical structure of the new compound was determined on the basis of spectroscopic analyses including 1D and 2D NMR data. Among isolates, compound 3 exhibited potent cytotoxic activities against SK-OV-3, SK-MEL-2, and XF498 cell lines (IC₅₀ = 5.91, 4.22, and 6.28 μM, respectively). Also, Compounds 9 and 10 showed strong anti-neuroinflammatory activities (IC₅₀ 2.38, and 6.70 μM, respectively).     

Xanthine oxidase inhibitors isolated from Piper nudibaccatum

Two new hydroxychavicol analogs nudibaccatumin A (1) and B (2), together with twenty known compounds were isolated from the methanol extract of Piper nudibaccatum. Their structures were elucidated by extensive spectroscopic analyses (1D and 2D NMR, HRESIMS, UV, IR and polarimetry). Hydroxychavicol is a known inhibitor of xanthine oxidase (XO). In the present study, hydroxychavicol and 5 natural analogs (1–5) were evaluated for their XO inhibitory activity. Neotaiwanensol B (3) (IC₅₀ = 0.28 μM) showed a greater inhibitory effect than hydroxychavicol and allopurinol (the positive control). Two new compounds 1 and 2 showed a moderate inhibition activity with an IC₅₀ value of 62.94 μM and 70.67 μM, respectively.     

Cytotoxic acridone and indoloquinazoline alkaloids from Zanthoxylum poggei

Two new alkaloids, poggeicridone (1) and 2-methoxy-7,8- dehydroruteacarpine (6), together with nine known compounds, were isolated from the dichloromethane (DCM) extract of the bark of Zanthoxylum poggei (Engl.) P. G. Waterman. The structures of all compounds were determined by comprehensive spectroscopic analyses (1D and 2D NMR and EI- and ESI⿿MS). Compounds 5-9 exhibited strong suppressive effects on the phagocytosis response upon activation with serum opsonized zymosan in the in vitro oxidative burst studies using whole blood. The IC₅₀ values were in the range of 12.0⿿25.9 μM. These compounds displayed a moderate level of cytotoxic activity against the human Caucasian prostate adenocarcinoma cell line PC-3, with IC₅₀ values of 15.8 and 22.1 μM (the IC₅₀ value of the positive control standard doxorubicin was IC₅₀ 0.9 μM). All isolated compounds were also tested against plant pathogenic bacteria, fungi and oomycetes using the paper disk agar diffusion assay, resulting in no significant activities (MICs > 1 mg/mL).     

Aspernolides F and G,new butyrolactones from the endophytic fungus Aspergillus terreus

Two new butyrolactones: aspernolides F (6) and G (7), together with three stigmasterol derivatives: (22E,24R)-stigmasta-5,7,22-trien-3-β-ol (1), stigmast-4-ene-3-one (2), and stigmasta-4,6,8(14), 22-tetraen-3-one (3), two meroterpenoids: terretonin A (4) and terretonin (5), and a butyrolactone derivative: butyrolactone VI (8) have been isolated from the endophytic fungus Aspergillus terreus isolated from the roots of Carthamus lanatus (Asteraceae). Their structures were determined by spectroscopic means (1D, 2D NMR, and HRESIMS), as well as optical rotation measurement and comparison with literature data. The isolated compounds were evaluated for their anti-microbial, anti-malarial, anti-leishmanial, and cytotoxic activities. Compound 1 displayed a potent activity against MRSA and C. neoformans with IC₅₀ values of 0.96 μg/mL and 4.38 μg/mL, respectively compared to ciprofloxacin (IC₅₀ 0.07 μg/mL) and amphotericin B (IC₅₀ 0.34 μg/mL), respectively. While, 6 showed good activity against C. neoformans (IC₅₀ 5.19 μg/mL) and mild activity against MRSA (IC₅₀ 6.39 μg/mL). Moreover, 1 and 2 exhibited very good anti-leishmanial activity towards L. donovani with IC₅₀ values of 4.61 and 6.31 μg/mL, respectively and IC₉₀ values of 6.02 and 16.71 μg/mL, respectively.     

Tirucallane triterpenoids from the stem bark of Araliopsis synopsis

Two new tirucallane triterpenoids, 21-methoxy-21,23-epoxy-tirucalla-7,24-dien-3α-ol (1) and 21-methoxy-21,23-epoxy-tirucalla-7,24-diene-1α,3α-diol (2), together with thirteen known compounds were isolated from the CH₂Cl₂ extract of the stem bark of Araliopsis synopsis. The structures of the compounds were determined by comprehensive analyses of their 1D and 2D NMR, mass spectral (EI and ESI) data and comparison with previously known analogs. Compounds 1–10 were tested against bacteria, fungi and plant pathogen oomycetes by the paper disk agar diffusion assay resulting in missing to low activities corresponding with MICs > 1 mg/mL. However, compounds 5–10 exhibited high cytotoxic activity against the human Caucasian prostate adenocarcinoma cell PC-3 line, with IC₅₀ 8.5–12.5 μM compared to the standard Doxorubicin with IC₅₀ = 0.9 μM, while compounds 1, 3 and 4 showed low activity.     

Chemical constituents of Ligularia alticola Worosch. leaves and their biological activities

Seven eremophilane-type sesquiterpenes (1–7), six cycloartane derivatives (8–13) and α-amyrin acetate (14) were isolated from the leaves of the far-eastern plant Ligularia alticola Worosch. (Family Asteraceae). (4S,5R,8S,10R)-8-Ethoxyeremophil-7(11)-en-12(8)-olide (1), 8α,11-epidioxy-8β-methoxyeremophil-6-ene (2) and 29-norcycloartan-3α-ol (8) have not been previously reported. Fukinone α-epoxide (3) was isolated for the first time from a natural source. The structures of all the compounds were established by the extensive analysis of their 1D and 2D NMR spectra and HR ESI mass spectrometry. The absolute stereochemistry of 1 was determined by comparison of theoretical and experimental ECD spectra with the application of B3LYP-TDDFT and B3LYP-GIAO calculations as well as by NMR spectroscopy. Compound 1 showed cytotoxic action against human cancer HL-60, Raji, and THP-1 cell lines (IC₅₀ 12.6, 6.0 and 6.9 μM, respectively). Compounds 2 and 4 demonstrated significant cytotoxic activities against HL-60 (IC₅₀ 2.8 and 5.8 μM, respectively) and Raji cells (IC₅₀ 2.9 and 4.2 μM, respectively). Compound 6 was cytotoxic against Raji cells (IC₅₀ 4.6 μM). None of tested compounds were cytotoxic against RAW 264.7 cells. Compounds 1 and 4–7 significantly decreased intracellular ROS levels, induced by endotoxic LPS from Escherichia coli in RAW 264.7 murine macrophages.     

Isolation of antiplasmodial anthraquinones from Kniphofia ensifolia,and synthesis and structure–activity relationships of related compounds

Bioassay-guided separation of the South African plant Kniphofia ensifolia for antiplasmodial activity led to the isolation of two new anthraquinones, named kniphofiones A and B (3 and 4), together with three known bioactive anthraquinone monomers (1, 2 and 5), and four known bisanthraquinones (6–9). The structures of the two new compounds were elucidated based on analyses of their 1D and 2D NMR spectra and mass spectrometric data. The dimeric compounds 6 and 7 displayed the strongest antiplasmodial activity among all the isolated compounds, with IC₅₀ values of 0.4 ± 0.1 and 0.2 ± 0.1 μM, respectively. The two new compounds displayed modest activities, with IC₅₀ values of 26 ± 4 and 9 ± 1 μM, respectively. Due to the synthetic accessibility of the new compounds and the increased activity shown by the dimeric compounds, a structure–activity relationship study was conducted. As a result, one analogue of kniphofione B (4), the caffeic acid derivative of aloe-emodin, was found to have the highest activity among all the aloe-emodin derivatives, with an IC₅₀ value of 1.3 ± 0.2 μM.     

Daphnane-type diterpenes with inhibitory activities against human cancer cell lines from Daphne genkwa

Four new daphnane-type diterpenes, genkwadanes A–D (1–4), together with 19 known ones, were isolated from ethanol extract of the flower buds of Daphne genkwa. Their structures were determined on the basis of extensive spectroscopic data. Among them, daphnane-type diterpene with a 1,10-double bond (1) was isolated from this plant for the first time. The cytotoxicity of all compounds 1–23 against the 10 selected human cancer cell lines was assayed. A number of compounds exhibited significant activities against the 10 cancer cell lines (IC₅₀ < 9.56 μM). and most interestingly, all the compounds revealed preferred cytotoxicities on the HT-1080 cell line and displayed much stronger inhibitory activities (IC₅₀ < 29.94 μM) compared with positive control 5-fluorouracil (IC₅₀ = 35.62 μM), particularly, compounds 9–11, 13, 16 and 19 exhibited the strongest cytotoxicity activities against the HT-1080 cell line (IC₅₀ < 0.1 μM).     

Acridone alkaloids from Vepris verdoorniana (Excell & Mendonça) Mziray (Rutaceae)

Two new acridone alkaloids, verdoocridone A (1) and B (4), together with fifteen known compounds were isolated from methanol extracts of the roots and leaves of Vepris verdoorniana. The structures of all compounds were determined by comprehensive spectroscopic analyses (1D and 2D NMR, EI- and ESI–MS). The ¹³C NMR values of 1,2,3,5-tetramethoxy-N-methylacridone (2) and 5-methoxyaborinine (3) are also reported. The crude extracts and compounds (1-6) were tested for their antimicrobial activity. The test delivered moderate activities for crude extracts and compounds 1, 5 and 6 against the bacterium Staphylococcus aureus and the fungi Mucor meihei and Candida albicans with MIC values between 115 and 180 μg/mL for extracts and between 21.3 and 29.4 μM for compounds, compared to gentamycin with 0.2 μM and nystatin with 5.2 μM against both fungi. The determination of the radical scanvenging activity using 1,1-dephenyl-2-picrylhydrazyl (DPPH) assay gave moderate antioxidant values for all tested compounds, with IC₅₀ between 0.29 and 0.41 μM, compared to the standard 3-t-butyl-4-hydroxyanisole (BHA) displaying 0.03 μM.     

Synthesis of novel pyrazole–thiadiazole hybrid as potential potent and selective cyclooxygenase-2 (COX-2) inhibitors

A series of 1,3,4-trisubstituted pyrazole derivatives (3a–f), (4a–f), and (5a–f) have been synthesized and evaluated for their cyclooxygenase (COX-1 and COX-2) inhibitory activity. The structures of newly synthesized compounds were characterized by IR, ¹H NMR, and mass spectral analysis. All of the compounds showed good inhibition of COX-2 with IC₅₀ of 1.33–17.5 μM. Among these derivatives, compound (5c) was the most potent and selective COX-2 inhibitor (IC₅₀ = 1.33 μM), with a significant selectivity index (SI >60). Molecular docking studies were carried out in order to predict the hypothetical binding mode of these compounds to the COX-2 isoenzyme. The result of present study suggests that pyrazole–thiadiazole hybrid could be an interesting approach for the design of new selective COX-2 inhibitory agents.     

Antiviral anthraquinones from the roots of Knoxia valerianoides

Three new anthraquinones, (2S)-8-carboxy-9-hydroxy-2-(2-hydroxypropan-2-yl)-1,2-dihydroanthra[2,1-b]furan-6,11-dione (1), 1,2,3,6-tetrahydroxy-9,10-anthraquinone (2), and 1,2,3,5,6-pentahydroxy-9,10-anthraquinone (3), as well as four known 9,10-anthraquinones (4–7) and five known triterpenes (8–12), were isolated from the roots of Knoxia valerianoides. Their structures and the absolute configuration of 1 were determined through interpretation of spectroscopic data, including UV, IR, NMR and CD spectra. The isolates were evaluated for their antiviral activities, and compounds 1 and 4 showed inhibitory effects on Coxsackie virus B3 replication with IC₅₀ values of 19.24 μM and 11.11 μM, respectively. Compound 4 showed activity against influenza virus A/Hanfang/359/95 with an IC₅₀ value of 11.11 μM.     

Two new 1,4-naphthoquinone derivatives from Impatiens balsamina L. flowers

Two new 1,4-naphthoquinone derivatives, balsaminone D (1), balsaminone E (2) along with two known compounds (3 and 4) were discovered from Impatiens balsamina L. flowers. Their structures were identified with spectroscopic methods including HR–EI–MS, 1D and 2D NMR, as well as the absolute configuration was determined by ECD calculation. In addition, new compounds 1 and 2 with IC₅₀ value of 30.54 and 40.67 μg/mL exhibited better activities against activated t-HSC/Cl-6 cells than positive control Silymarin and Fufang Biejia Ruangan Pian, of which the IC₅₀ value were 202.34 and 231.56 μg/mL, respectively.     

Melanogenesis inhibitory activity of a 7-O-9′-linked neolignan from Alpinia galanga fruit

An aqueous acetone extract from the fruit of Alpinia galanga (Zingiberaceae) demonstrated inhibitory effects on melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells (IC₅₀ = 7.3 μg/mL). Through bioassay-guided separation of the extract, a new 7-O-9′-linked neolignan, named galanganol D diacetate (1), was isolated along with 16 known compounds including 14 phenylpropanoids (2–15). The structure of 1, including its absolute stereochemistry in the C-7 position, was elucidated by means of extensive NMR analysis and total synthesis. Among the isolates, 1 (IC₅₀ = 2.5 μM), 1′S-1′-acetoxychavicol acetate (2, 5.0 μM), and 1′S-1′-acetoxyeugenol acetate (3, 5.6 μM) exhibited a relatively potent inhibitory effect without notable cytotoxicity at effective concentrations. The following structural requirements were suggested to enhance the inhibitory activity of phenylpropanoids on melanogenesis: (i) compounds with 4-acetoxy group exhibit higher activity than those with 4-hydroxy group; (ii) 3-methoxy group dose not affect the activity; (iii) acetylation of the 1′-hydroxy moiety enhances the activity; and (iv) phenylpropanoid dimers with the 7-O-9′-linked neolignan skeleton exhibited higher activity than those with the corresponding monomer. Their respective enantiomers [1′ (IC₅₀ = 1.9 μM) and 2′ (4.5 μM)] and racemic mixtures [(±)-1 (2.2 μM) and (±)-2 (4.4 μM)] were found to exhibit melanogenesis inhibitory activities equivalent to those of the naturally occurring optical active compounds (1 and 2). Furthermore, the active compounds 1–3 inhibited tyrosinase, tyrosine-related protein (TRP)-1, and TRP-2 mRNA expressions, which could be the mechanism of melanogenesis inhibitory activity.     

Voulkensin C–E,new 11-oxocassane-type diterpenoids and a steroid glycoside from Caesalpinia volkensii stem bark and their antiplasmodial activities

A bioassay guided isolation of potential antimalarial molecules from the stem bark of Caesalpinia volkensii Harms (Fabaceae) achieved three new 11-oxocassane-type diterpenoids named voulkensin C (1), D (2) and E (3) together with one steroid glycoside named 3-O-[β-glucopyranosyl(1→2)-O-β-xylopyranosyl]-stigmasterol (4) and seven other known compounds including stigmasterol (5), β-sitosterol (6), oleanolic acid (7), 3-β-acetoxyolean-12-en-28-methyl ester (8), voucap-5-ol (9), caesadekarin C (10), deoxycaesaldekarin C (11). The structures of the new compounds were determined on the basis of extensive spectroscopic data (IR, MS, ¹H and ¹³C NMR and 2D NMR) analyses. The polar extracts revealed moderate to good antiplasmodial activities against chloquine-sensitive (D6) and -resistant strains (W2) of Plasmodium falciparum. Whereas the pure isolates exhibited limited to moderate antiplasmodial activities with compound 4 showing the highest antiplasmodial activities (IC₅₀ values of 4.44 ± 0.88 and 2.74 ± 1.10 μM against D6 and W2 strains, respectively). These results suggest a possible contribution of phytochemicals from C. volkensii stem bark towards inhibition of plasmodial parasites’ growth hence potential antimalarial.     

New prenylated isoflavonoids as protein tyrosine phosphatase 1B (PTP1B) inhibitors from Erythrina addisoniae

Bioassay-guided fractionation of the EtOAc extract of the root of Erythrina addisoniae (Leguminosae) resulted in the isolation of four new (1–4), along with 2 known prenylated isoflavonoids (5–6). The structures of the isolates were assigned on the basis of spectroscopic data analysis, focusing on interpretation of 1D and 2D NMR, and MS data. All the isolates were evaluated for their inhibitory effects on protein tyrosine phosphatase 1B (PTP1B), as well as their growth inhibition on MCF7, adriamycin-resistant MCF7 (MCF7/ADR), and MDA-MB-231 breast cancer cell lines. Compounds which exhibited PTP1B inhibitory activity (IC₅₀ values ranging from 4.6 ± 0.3 to 24.2 ± 2.1 μM) showed potential cytotoxic activity (IC₅₀ values ranging from 3.97 ± 0.17 to 11.4 ± 1.9 μM). Taken together, our data suggest that prenylated isoflavonoids, especially the isoflavone-type skeleton could be considered as new lead compounds against breast cancer via PTP1B inhibition.     

Hirtellanines A and B,a pair of isomeric isoflavonoid derivatives from Campylotropis hirtella and their immunosuppressive activities

A pair of isomeric isoflavonoid derivatives, Hirtellanines A (1) and B (2), has been isolated from the roots of Campylotropis hirtella (Franch.) Schindl. and their structures were elucidated on the basis of spectroscopic methods, with special emphasis on 1D and 2D NMR techniques. The in vitro assay showed that Hirtellanine A had strong B lymphocyte suppression activity (IC₅₀: 0.06 μM) and T lymphocyte suppression activity (IC₅₀: 0.92 μM). Hirtellanine B showed moderate B lymphocyte suppression activity (IC₅₀: 3.00 μM) and T lymphocyte suppression activity (IC₅₀: 9.55 μM). Due to the potent immunosuppressive activities and lower cytotoxicity, Hirtellanine A could be a promising lead towards novel immunosuppressive agents.