Antifungal compounds from turmeric and nutmeg with activity against plant pathogens

The antifungal activity of twenty-two common spices was evaluated against plant pathogens using direct-bioautography coupled Colletotrichum bioassays. Turmeric, nutmeg, ginger, clove, oregano, cinnamon, anise, fennel, basil, black cumin, and black pepper showed antifungal activity against the plant pathogens Colletotrichum acutatum, Colletotrichum fragariae, and Colletotrichum gloeosporioides. Among the active extracts, turmeric and nutmeg were the most active and were chosen for further investigation. The bioassay-guided fractionation led to the isolation of three compounds from turmeric (1–3) and three compounds from nutmeg (4–6). Their chemical structures were elucidated by spectroscopic analysis including HR-MS, 1D, and 2D NMR as curcumin (1), demethoxycurcumin (2) and bisdemethoxy-curcumin (3), erythro-(7R,8R)-Δ^8′-4,7-dihydroxy-3,3′,5′-trimethoxy-8-O-4′-neolignan (4), erythro-(7R,8R)-Δ8′-7-acetoxy-3,4,3′,5′-tetra-methoxy-8-O-4′-neolignan (5), and 5-hydroxy-eugenol (6). The isolated compounds were subsequently evaluated using a 96-well microbioassay against plant pathogens. At 30 μM, compounds 2 and 3 possessed the most antifungal activity against Phomopsis obscurans and Phomopsis viticola, respectively.     

Three new phenolic compounds from the roots of Glycyrrhiza yunnanensis

Three new phenolic compounds (1–3), together with 16 known compounds (4–19), were isolated from the roots of Glycyrrhiza yunnanensis Cheng f. et L. K. Dai. On the basis of 1D and 2D NMR, HR-ESI-MS, and circular dichroism (CD) spectroscopic analysis, structures of the new compounds were elucidated as 2-(2′-methoxy-4′-hydroxy)-aryl-3-methy-6-hydroxy-benzofuran (1), (2S)-6,7-(2,2-dimethyldihydropyrano)-8-prenyl-4′-hydroxyflavanone (2), and 6-prenyl-7,3′,4′-trihydroxyflavone (3). Compounds 1, 3, 5, 12, 14, 15 and 16 showed antioxidant activity by an ABTS-based assay.     

Alkyl and phenolic glycosides from Saussurea stella

One alkyl glycoside, saussurostelloside A (1), two phenolic glycosides, saussurostellosides B1 (2) and B2 (3), and 27 known compounds, including eleven flavonoids, seven phenolics, six lignans, one neolignan, one phenethyl glucoside and one fatty acid, were isolated from an ethanol extract of Saussurea stella (Asteraceae). Their structures were elucidated by NMR, MS, UV, and IR spectroscopic analysis. Of the known compounds, (+)-medioresinol-di-O-β-d-glucoside (7), picraquassioside C (10), and diosmetin-3′-O-β-d-glucoside (27) were isolated from the Asteraceae family for the first time, while (+)-pinoresinol-di-O-β-d-glucoside (6), di-O-methylcrenatin (11), protocatechuic acid (14), 1,5-di-O-caffeoylquinic acid (17), formononetin (28), and phenethyl glucoside (29) were isolated from the Saussurea genus for the first time. The anti-inflammatory activities of three new compounds (1–3), five lignans ((−)-arctiin (4), (+)-pinoresinol-4-O-β-d-glucoside (5), (+)-pinoresinol-di-O-β-d-glucoside (6), (+)-medioresinol-di-O-β-d-glucoside (7) and (+)-syringaresinol-4-O-β-d-glucoside (8)), one neolignan (picraquassioside C (10)), and one phenolic glycoside (di-O-methylcrenatin (11)) were evaluated by testing their inhibition of the release of β-glucuronidase from PAF-stimulated neutrophils. Only compound 5 showed moderate inhibition of the release of β-glucuronidase, with an inhibition ratio of 39.1%.     

Rigenolide A,a new secoiridoid glucoside with a cyclobutane skeleton,and three new acylated secoiridoid glucosides from Gentiana rigescens Franch

Rigenolide A (1), a new secoiridoid glucoside with a cyclobutane skeleton and three new acylated secoiridoid glucosides, 2′-(2,3-dihydroxybenzoyl)-gentiopicroside (2), 2′-(2,3-dihydroxybenzoyl)-swertiamarin (3), 3′-(2,3-dihydroxybenzoyl)-sweroside (4), along with two noriridoids (7 and 8) and two known secoiridoid glucosides (5 and 6), were isolated from Gentiana rigescens Franch. The structures of new compounds were elucidated by extensive spectroscopic analyses. The isolated compounds were evaluated for DPPH free-radical scavenging activity.     

Flavonoids and stilbenoids from Derris eriocarpa

One new resveratrol analogue, 1-(3′,4′,5′-trimethoxyphenyl)-2-methoxy-2-(4″-methoxyphenyl)-ethane-1-ol (1), and two new prenylisoflavones, 4′-hydroxy-5,7-dimethoxy-6-(3-methyl-2-butenyl)-isoflavone (2), and derrubon 5-methyl ether (3), together with 17 known compounds including one new natural product, 5,7-dihydroxy-3-[4′-O-(3-methyl-2-butenyl)-phenyl]-isoflavone (4), were isolated from the stems of ethnomedicinal plant Derris eriocarpa How. (Leguminosae). Their structures were elucidated based on chemical evidence and spectroscopic techniques including two-dimensional NMR methods. All compounds are reported from this species for the first time. Antimicrobial activities of the new compounds were evaluated. Compound 2 exhibited good inhibitory activities against Candida guilliermondii, C. albicans and Microsporium gypseum with the minimal inhibitory concentration (MIC) values of 12.5 μg/ml.     

Dihydrochalcones and homoisoflavanes from the red resin of Dracaena cochinchinensis (Chinese dragon's blood)

Two new dihydrochalcones, 4-hydroxy-2,4′-dimethoxydihydrochalcone (1) and 3,4′-dihydroxy-2,4,6-trimethoxydihydrochalcone (2), and a new homoisoflavane, 7,3′-dihydroxy-8,4′-dimethoxyhomoisoflavane (3), along with 12 known compounds (4–15), were isolated from the red resin of Dracaena cochinchinensis (Chinese dragon's blood). Their structures were assigned by a variety of spectroscopic techniques. Diversity of cleavage pathways were proposed for dihydrochalcones and homoisoflavanes based on the mass spectroscopic behaviors of those identified compounds using hybrid ion trap-time of flight mass spectrometry. All the compounds were evaluated for their inhibitory effects on nitric oxide production in lipopolysaccharide-induced RAW 264.7 macrophages, and compound 9 exhibited mild inhibition of NO production in this assay with IC₅₀ value of 50.3 μM.     

The antifungal constituents from the seeds of Itoa orientalis

Three new phenolic constituents, itolide A (1), itolide B (2), itoside P (3), and 1D-3-deoxy-3-hydroxymethyl-myo-inositol (4), which is described herein for the first time as a natural product, were isolated along with four other known compounds (5 to 8) from the methanol extract of the seeds of Itoa orientalis Hemsl by the activity-guided fractionation. Their structures were determined by spectroscopic means. Compounds 1 to 8 exhibited antifungal activities against Sclerotium rolfsii with IC₅₀ values ranging from 60.12 to 240.00 μM and against Rhizoctonia solani with IC₅₀ values ranging from 45.34 to 233.14 μM, respectively, and compounds 1, 2, 5 exhibited cytotoxic activity against Tn5B1-4 insect cell line with EC₅₀ values of 203.68, 93.41 and 40.37 μM, respectively.     

Three pairs of variecolortide enantiomers from Eurotium sp. with caspase-3 inhibitory activity

7-O-methylvariecolortide A (1), variecolortide B (2), and variecolortide C (3), the rare variecolortides existing in racemic manner, were isolated from an endolichenic fungal strain Eurotium sp. (No. 17-11-8-1). With the chiral HPLC technology, (−)-(S)-7-O-methylvariecolortide A (1a), (+)-(R)-7-O-methylvariecolortide A (1b), (−)-(S)-variecolortide B (2a), (+)-(R)-variecolortide B (2b), (−)-(S)-variecolortide C (3a), and (+)-(R)-variecolortide C (3b) were successfully separated and obtained. Their absolute configurations were firstly assigned by ECD experiment and ECD calculation. According to the relation of isolated compounds, a plausible biosynthetic pathway for variecolortides was proposed. In caspase-3 enzymatic assay, compounds 1–3 showed inhibitory activity, with IC₅₀ values of 1.7, 0.8 and 15.7 μM, respectively.     

Antibacterial anthranilic acid derivatives from Geijera parviflora

Five anthranilic acid derivatives, a mixture I of three new compounds 11′-hexadecenoylanthranilic acid (1), 9′-hexadecenoylanthranilic acid (2), and 7′-hexadecenoylanthranilic acid (3), as well as a new compound 9,12,15-octadecatrienoylanthranilic acid (4) together with a new natural product, hexadecanoylanthranilic acid (5), were isolated from Geijera parviflora Lindl. (Rutaceae). Their structures were elucidated by extensive spectroscopic measurements, and the positions of the double bonds in compounds 1–3 of the mixture I were determined by tandem mass spectrometry employing ozone-induced dissociation. The mixture I and compound 5 showed good antibacterial activity against several Gram-positive strains.     

Cytotoxic prenylated bibenzyls and flavonoids from Macaranga kurzii

One unique prenylated bibenzyl, kurzphenol A (1), two new prenylated flavonoids, kurzphenols B and C (2 and 3), as well as fourteen known compounds (4–17) were isolated from the twigs of Macaranga kurzii. Compound 1 was the first example of prenylated bibenzyl which possesses a benzofuran ring. All the known compounds were isolated from M. kurzii for the first time. Their structures were elucidated on the basis of extensive spectroscopic interpretation. Compounds 1–17 were tested for their cytotoxicity against A-549 and Hep G2 cancer cell lines and showed IC₅₀ values in the range of 9.76–30.14 μg/mL.     

Iridoid and bis-iridoid glucosides from the fruit of Gardenia jasminoides

Three new iridoid glucosides, 6″-O-trans-feruloylgenipin gentiobioside (1), 2′-O-trans-caffeoylgardoside (2), jasmigeniposide A (3), and one new bis-iridoid glucoside, jasmigeniposide B (4), along with six known analogues (5–10), were isolated from the fruit of Gardenia jasminoides. Their structures were established on the basis of spectroscopic analyses and chemical methods. Anti-virus activity of isolated compounds were evaluated in vitro and only compound 9 showed moderate inhibitory activity against H1N1 with 50% effective concentration (EC₅₀) value of 104.36 μM, and selective index (SI) value greater than 4.79.     

Four new sesquiterpene lactones from the stem bark of Illicium burmanicum

Four new sesquiterpene lactones (1), (2), (3), and (4), along with three known sesquiterene, namely, 6,7,10-trihydoxyisodaucane (5), 4β,10β-dihydroxyaromadendrane (6), and sescrassidiol (7) were isolated from the stem bark of Illicium burmanicum. The structures of the new compounds were determined using 1D and 2D NMR, and HRESIMS. The anti-inflammatory activities of these compounds were evaluated by measuring the enzymatic activity of luciferase in NF-κB reporters in a (Luc)-HEK 293 cell line treated with lipopolysaccharide (LPS).     

Caffeoylquinic acid derivatives isolated from the aerial parts of Gynura divaricata and their yeast α-glucosidase and PTP1B inhibitory activity

The phytochemical investigation of natural products of Gynura divaricata led to the isolation of eleven caffeoylquinic acid derivatives. They were characterized by spectrometric methods as 5-O-caffeoylquinic acid (1), 5-O-p-coumaroylquinic acid (2), 5-O-feruloylquinic acid (3), methyl 5-O-caffeoylquinate (4), 3,4-dicaffeoylquinic acid (5), 3,5-dicaffeoylquinic acid (6), 4,5-dicaffeoylquinic acid (7), methyl 3,4-dicaffeoylquinate (8), methyl 3,5-dicaffeoylquinate (9), methyl 4,5-dicaffeoylquinate (10) and ethyl 4,5-dicaffeoylquinate (11). The individual compounds were screened for the inhibition of yeast α-glucosidase and Protein Tyrosine Phosphatase 1B (PTP1B) using in vitro assays. Among the isolated compounds, 3,4-dicaffeoylquinic acid (5), 4,5-dicaffeoylquinic acid (7), methyl 3,4-dicaffeoylquinate (8) and methyl 4,5-dicaffeoylquinate (10) exhibited significant inhibitory activities against α-glucosidase. In addition, 5-O-p-coumaroylquinic acid (2), 3,5-dicaffeoylquinic acid (6) and 4,5-dicaffeoylquinic acid (7) had considerable inhibitory effect against PTP1B. Based on these findings, the caffeoylquinic acid derivatives were deduced to be potentially responsible for the anti-diabetic activity of G. divaricata. The preliminary structure–activity relationship study suggests that the number and positioning of caffeoyl groups in the quinic acid derivatives are important for both α-glucosidase and PTP1B inhibitory potency. Moreover, the corresponding methyl esters of some dicaffeoylquinic acids have enhanced inhibitory activity against yeast α-glucosidase.     

Cytotoxic effect of triterpenoids from the root bark of Hibiscus syriacus

In this study, 4 new triterpenoids—3β- acetoxy-olean-11-en,28,13β-olide (1), 3β- acetoxy-11α,12α-epoxy-olean-28,13β-olide (2), 19α-epi-betulin (3), and 20, 28-epoxy-17β,19β-lupan-3β-ol (4)—and 12 known compounds, were isolated from the root bark of Hibiscus syriacus L. by using acetone extraction. Their structures were characterized by extensive spectroscopic analysis. To investigate cytotoxicity, A549 human lung cancer cells were exposed to the extract and the compounds identified from it. Significantly reduced cell viability was observed with betulin-3-caffeate (12) (IC₅₀, 4.3 μM). The results of this study indicate that betulin-3-caffeate (12) identified from H. syriacus L. may warrant further investigation for potential as anticancer therapies.     

Mangostanaxanthones I and II,new xanthones from the pericarp of Garcinia mangostana

Two new xanthones: mangostanaxanthones I (3) and II (5) were isolated from the pericarp of Garcinia mangostana, along with four known xanthones: 9-hydroxycalabaxanthone (1), parvifolixanthone C (2), α-mangostin (4), and rubraxanthone (6). Their structures were elucidated on the basis of IR, UV, 1D, 2D NMR, and MS spectroscopic data, in addition to comparison with literature data. The isolated compounds were evaluated for their antioxidant, antimicrobial, and quorum-sensing inhibitory activities. Compounds 3 and 5 displayed promising antioxidant activity with IC₅₀ 12.07 and 14.12 μM, respectively using DPPH assay. Compounds 4–6 had weak to moderate activity against Escherichia coli and Staphylococcus aureus, while demonstrated promising action against Bacillus cereus with MICs 0.25, 1.0, and 1.0 mg/mL, respectively. The tested compounds were inactive against Candida albicans. However, they showed selective antifungal potential toward Aspergillus fumigatus. Compounds 3 and 4 possessed quorum-sensing inhibitory activity against Chromobacterium violaceum ATCC 12472.     

Pregnane alkaloids from Sarcococca hookeriana var. digyna

Fourteen pregnane-type steroidal alkaloids were isolated from the ethanolic extracts of whole Sarcococca hookeriana var. digyna plants. Their structures were elucidated on the basis of spectral data. Three of them were identified as new steroidal alkaloids: (S)-20-(N,N-dimethylamino)-16α,17α-epoxy-3β-methoxy-pregn-5-ene (1), (20S)-20-(N,N-dimethylamino)-3β-tigloylamino-5α-pregn-11β-ol (2), and (20S)-2α,4β-bis(acetoxy)-20-(N,N-dimethylamino)-3β-tigloylamino-5α-pregnane (3). Some of the isolated compounds showed estrogen biosynthesis-promoting effects in human ovarian granulosa-like KGN cells. The EC₅₀ values for the most effective compounds, vagnine B (6) and funtumafrine C (12), were 71 μM and 67 μM, respectively.     

Phenylethanoid glycosides from the stems of Callicarpa peii (hemostatic drug)

Two new trisaccharide intermediates of phenylethanoid glycosides, peiioside A₁/A₂ (1a/1b) and peiioside B (2), were isolated from the n-BuOH fraction of MeOH extract of the stems of Callicarpa peii H.T. Chang, together with five biogenetic relevant known compounds 3–7. The structures of compounds 1 and 2 were elucidated by extensive spectroscopic methods (especially 2D-NMR techniques) and acid-catalyzed hydrolysis as O-α-l-rhamnopyranosyl-(1″ → 3′)-O-[β-d-apiofuranosyl-(1‴ → 6′)] -4′-O-[(E)-caffeoyl]-d-glucopyranoside] (1a/1b), 3,4-dihydroxy-β-phenylethoxy-O-[β-d-apiofuranosyl-(1‴ → 6′)-α-l-rhamnopyranosyl-(1″ → 3′)-O-β-d-glucopyranoside] (2), respectively. On the basis of the isolated compounds, a presumable biogenetic pathway of the biologically interesting phenylethanoid glycosides about forsythoside B (3) and acteoside (4) isolated from this species was proposed. Isolation of five related intermediates (1–2, 5–7) provided further support for the biogenetic path. This is the first report about phytochemical research on C. peii and the biogenetic hypothesis of forsythoside B and acteoside.     

Isolation of new flavan-3-ol and lignan glucoside from Loropetalum chinense and their antimicrobial activities

Phytochemical and antimicrobial activity study on the ethanol extract of the leaves and stems of Loropetalum chinense led to the isolation of a new flavan-3-ol compounds, 8-[1-(3,4-dihydroxyphenyl)-3-methoxy-3-oxopropyl]-catechin (loropetaliside A) (1) and a new lignan glucoside, 1-(5-hydroxy-3-methoxyphenyl)-2-(2-β-glucopyranosyl-4-hydroxy-5-(1-(E)propen-3-ol)-phenyl)-propane-3-ol (loropetaliside B) (3) and several known compounds manglieside D (2), quercetin (4), kaempferol-3-O-D-glucopyranoside (5), quercetin-3-O-β-L-rhamnoside (6) and tiliroside (7). Their structures were elucidated on the basis of extensive spectroscopic analysis.     

Four new bis-iridoids isolated from the traditional Tibetan herb Pterocephalus hookeri

Pterocenoids A–E (1–4), which Pterocenoids A(1) is one novel dimer containing a pyridine monoterpene alkaloid; and Pterocenoids B–E (2–4) are rare arranged non-glycosidic bis-iridoids were isolated from Pterocephlus hookeri. The structures of the compounds were established by 1D and 2D NMR spectroscopy and mass spectrometry. All bis-iridoids isolated from P. hookeri were found to possess secoiridoid/iridoid subtype skeletons. Hence, bis-iridoids can be regarded as the chemotaxonomic markers of P. hookeri. The origins of the new bis-iridoids (1–4) were postulated and their activities of inhibition of the NF-κB pathway were assayed and compounds 1–3 showed moderate activity in inhibiting NF-κB.     

Chemical constituents of Aloe barbadensis Miller and their inhibitory effects on phosphodiesterase-4D

Aloe barbadensis Mill has been used as food and medicine for a long time. In order to investigate the chemical constituents of A. barbadensis and their inhibitory activities towards phosphodiesterase-4D (PDE4D), 70% methanol extract of the dried A. barbadensis powder was employed. Phytochemical investigation has led to the isolation of three new chromones, 5-(hydroxymethyl)-7-methoxy-2-methylchromone (4), 5-((4E)-2′-oxo-pentenyl)-2-hydroxymethylchromone (6), and 7-hydroxy-5-(hydroxymethyl)-2-methylchromone (7), together with eighteen known compounds. Their chemical structures were determined based on spectroscopic methods including UV, IR, 1D and 2D NMR, and HRMS spectrometry. In addition, their inhibition against PDE4D was evaluated using tritium-labeled adenosine 3′,5′-cyclic monophosphate (³H-cAMP) as the substrate. Inhibition was calculated by the variation of radioactivity after the reaction, and compounds 1–4, 10, and 21 exhibited certain inhibitory activities towards PDE4D, which can provide an explanation why A. barbadensis can serve as anti-inflammatory agents.