Comparative characterization of degraded and non-degradative hemicelluloses from barley straw and maize stems: Composition, structure, and thermal properties

Three organic solvents and one aqueous alkaline solution for fully fractional dissolving hemicelluloses from mild ball-milled cell wall of lignified barley straw and maize stems are described: 90% neutral dioxane, 80% dioxane containing 0.05 M HCl, dimethyl sulfoxide (DMSO), and 8% aqueous KOH. The four successive extractions resulted in dissolution of 94.6% and 96.4% of the original hemicelluloses and 93.7% and 95.3% of the original lignin from barley straw and maize stems, respectively. The structures of the hemicellulosic fractions released during the treatment with the neutral solvents of 90% dioxane and DMSO was found to remain intact, while the extractions with 80% acidic dioxane and 8% KOH under the conditions used resulted in a partial depolymerization of dissolved polysaccharides by cleavage of the glycosidic bonds and saponification of the ester groups in the polymers. The 90% neutral dioxane-soluble hemicellulosic fractions consisted mainly of the more branched arabinoxylans and mixed-linkage glucans such as β-glucans, whereas the hemicellulosic fractions solubilized during the sequential treatments with 80% acidic dioxane, DMSO, and 8% KOH are composed of arabino-(4-O-methyl-d-glucurono) xylans as the major hemicellulosic materials. In addition, the hemicellulosic polymers contained small amounts of ferulic and p-coumaric acids and lignins, revealing that the hemicelluloses removed are mostly unbound to the lignins in the cell walls of cereal straws. This non-degradative cell wall dissolution offers the potential to analyze polysaccharide components for the first time, and improve current hemicellulosic isolation method by using high concentration of aqueous alkali from the delignified cell walls.     

New Thymoquinol Glycosides and Neuroprotective Dibenzocyclooctane Lignans from the Rattan Stems of Schisandra chinensis

Three new lignans ( 1 – 3 ), together with four new thymoquinol glycosides ( 4 – 7 ), were isolated from 70%‐EtOH extract of the rattan stems of Schisandra chinensis. The structures of 1 – 7 were elucidated by detailed spectroscopic analyses, and these new compounds were identified as pinobatol‐9‐O‐β‐d ‐glucopyranoside ( 1 ), 1,2,13,14‐tetramethoxydibenzocyclooctadiene 3,12‐O‐β‐d ‐diglucopyranoside ( 2 ), 3,7‐dihydroxy‐1,2,13,14‐tetramethoxydibenzocyclooctadiene 12‐O‐β‐d ‐glucopyranoside ( 3 ), thymoquinol 2‐O‐β‐d ‐apiofuranosyl‐(1→6)‐β‐d ‐glucopyranoside ( 4 ), thymoquinol 2‐O‐α‐d ‐arabinofuranosyl‐(1→6)‐β‐d ‐glucopyranoside ( 5 ), thymoquinol 5‐O‐β‐d ‐apiofuranosyl‐(1→6)‐β‐d ‐glucopyranoside ( 6 ), and thymoquinol 5‐O‐α‐d ‐arabinofuranosyl‐(1→6)‐β‐d ‐glucopyranoside ( 7 ). The neuroprotective activity of 1 – 7 was evaluated on PC12 cells with neurotoxicity induced by amyloid‐beta 1 – 42 (Aβ_{1 – 42}). Compounds 2 and 3 showed protecting activity against Aβ‐induced toxicity in PC12 cells.     

Triterpene Saponins from the Roots of Ilex asprella

Six new triterpene saponins, ilexasprellanosides A–F ( 1 – 6 , resp.), together with eleven known compounds were isolated from the roots of Ilex asprella. The new saponins were characterized as ursa‐12,18‐dien‐28‐oic acid 3‐O‐β‐D ‐xylopyranoside ( 1 ), 19α‐hydroxyursolic acid 3‐O‐β‐D ‐(2′‐O‐acetylxylopyranoside) ( 2 ), 19α‐hydroxyursolic acid 3‐O‐β‐D ‐glucuronopyranoside ( 3 ), 3β,19α‐dihydroxyolean‐12‐en‐23,28‐dioic acid 28‐O‐β‐D ‐glucopyranoside ( 4 ), 19α‐hydroxyoleanolic acid 3‐O‐β‐D ‐(2′‐O‐acetylxylopyranoside) ( 5 ), 19α‐hydroxyoleanolic acid 3‐O‐β‐D ‐glucuronopyranoside ( 6 ). The structures of the new compounds were elucidated by analysis of their spectroscopic data and chemical degradation. Compounds 2, 4 , oleanolic acid 3‐O‐β‐D ‐glucuronopyranoside, 3‐β‐acetoxy‐28‐hydroxyurs‐12‐ene, and pomolic acid showed significant cytotoxic activities against human tumor cell line A549 (IC₅₀ values of 1.87, 2.51, 1.41, 3.24, and 5.63 μM , resp.).     

Inhibition of NO Production by Grindelia argentina and Isolation of Three New Cytotoxic Saponins

A bioassay‐guided phytochemical analysis of the ethanolic extract of Grindelia argentina Deble & Oliveira ‐Deble (Asteraceae) allowed the isolation of a known flavone, hispidulin, and three new oleanane‐type saponins, 3‐O‐β‐D ‐xylopyranosyl‐(1→3)‐β‐D ‐glucopyranosyl‐2β,3β,16α,23‐tetrahydroxyolean‐12‐en‐28‐oic acid 28‐O‐β‐D ‐xylopyranosyl‐(1→2)‐β‐D ‐apiofuranosyl‐(1→3)‐β‐D ‐xylopyranosyl‐(1→3)‐α‐L ‐rhamnopyranosyl‐(1→2)‐α‐L ‐arabinopyranosyl ester ( 2 ), 3‐O‐β‐D ‐glucopyranosyl‐2β,3β,23‐trihydroxyolean‐12‐en‐28‐oic acid 28‐O‐β‐D ‐xylopyranosyl‐(1→2)‐β‐D ‐apiofuranosyl‐(1→3)‐β‐D ‐xylopyranosyl‐(1→3)‐α‐L ‐rhamnopyranosyl‐(1→2)‐α‐L ‐arabinopyranosyl ester, ( 3 ) and 3‐O‐β‐D ‐xylopyranosyl‐(1→3)‐β‐D ‐glucopyranosyl‐2β,3β,23‐trihydroxyolean‐12‐en‐28‐oic acid 28‐O‐β‐D ‐xylopyranosyl‐(1→2)‐β‐D ‐apiofuranosyl‐(1→3)‐β‐D ‐xylopyranosyl‐(1→3)‐α‐L ‐rhamnopyranosyl‐(1→2)‐α‐L ‐arabinopyranosyl ester ( 4 ), named grindeliosides A–C, respectively. Their structures were determined by extensive 1D‐ and 2D‐NMR experiments along with mass spectrometry and chemical evidence. The isolated compounds were evaluated for their inhibitory activities against LPS/IFN‐γ‐induced NO production in RAW 264.7 macrophages and for their cytotoxic activities against the human leukemic cell line CCRF‐CEM and MRC‐5 lung fibroblasts. Hispidulin markedly reduced LPS/IFN‐γ‐induced NO production (IC₅₀ 51.4 μM ), while grindeliosides A–C were found to be cytotoxic, with grindelioside C being the most active against both CCRF‐CEM (IC₅₀ 4.2±0.1 μM ) and MRC‐5 (IC₅₀ 4.5±0.1 μM ) cell lines.     

Phenolic compounds from the whole plants of Gentiana rhodantha (Gentianaceae)

Gentiana rhodantha Franch. ex Hemsl. (Gentianaceae), an annual herb widely distributed in the southwest of China, has been medicinally used for the treatment of inflammation, cholecystitis, and tuberculosis by the local people of its growing areas. Chemical investigation on the whole plants led to the identification of eight new phenolic compounds, rhodanthenones A–D ( 1 – 4 , resp.), apigenin 7‐O‐glucopyranosyl‐(1→3)‐glucopyranosyl‐(1→3)‐glucopyranoside ( 5 ), 1,2‐dihydroxy‐4‐methoxybenzene 1‐O‐α‐L ‐rhamnopyranosyl‐(1→6)‐β‐D ‐glucopyranoside ( 6 ), 1,2‐dihydroxy‐4,6‐dimethoxybenzene 1‐O‐α‐L ‐rhamnopyranosyl‐(1→6)‐β‐D ‐glucopyranoside ( 7 ), and methyl 2‐O‐β‐D ‐glucopyranosyl‐2,4,6‐trihydroxybenzoate ( 8 ), together with eleven known compounds, 9 – 19 . Their structures were determined on the basis of detailed spectroscopic analyses and chemical methods. Acetylcholinesterase (AChE) inhibition and cytotoxicity tests against five human cancer cell lines showed that only rhodanthenone D ( 4 ) and mangiferin ( 12 ) exhibited 18.4 and 13.4% of AChE inhibitory effects at a concentration of 10⁻⁴ M , respectively, while compounds 1 – 5 and the known xanthones lancerin ( 11 ), mangiferin ( 12 ), and neomangiferin ( 13 ) displayed no cytotoxicity at a concentration of 40 μM .     

Melanogenesis‐Inhibitory and Cytotoxic Activities of Diarylheptanoids from Acer nikoense Bark and Their Derivatives

Nine cyclic diarylheptanoids, 1 – 9 , including two new compounds, i.e., 9‐oxoacerogenin A ( 8 ) and 9‐O‐β‐D ‐glucopyranosylacerogenin K ( 9 ), along with three acyclic diarylheptanoids, 10 – 12 , and four phenolic compounds, 13 – 16 , were isolated from a MeOH extract of the bark of Acer nikoense (Aceraceae). Acid hydrolysis of 9 yielded acerogenin K ( 17 ) and D ‐glucose. Two of the cyclic diarylheptanoids, acerogenin A ( 1 ) and (R)‐acerogenin B ( 5 ), were converted to their ether and ester derivatives, 18 – 24 and 27 – 33 , respectively, and to the dehydrated derivatives, 25, 26, 34 , and 35 . Upon evaluation of compounds 1 – 16 and 18 – 35 for their inhibitory activities against melanogenesis in B16 melanoma cells, induced with α‐melanocyte‐stimulating hormone (α‐MSH), eight natural glycosides, i.e., six diarylheptanoid glycosides, 2 – 4, 6, 9 , and 12 , and two phenolic glycosides, 15 and 16 , exhibited inhibitory activities with 24–61% reduction of melanin content at 100 μM concentration with no or almost no toxicity to the cells (88–106% of cell viability at 100 μM ). In addition, when compounds 1 – 16 and 18 – 35 were evaluated for cytotoxic activity against human cancer cell lines, two natural acyclic diarylheptanoids, 10 and 11 , ten ether and ester derivatives, 18 – 22 and 27 – 31 , and two dehydrated derivatives, 34 and 35 , exhibited potent cytotoxicities against HL60 human leukemia cell line (IC₅₀ 8.1–19.3 μM ), and five compounds, 10, 11, 20, 29 , and 30 , against CRL1579 human melanoma cell line (IC₅₀ 10.1–18.4 μM ).     

Four New Steroidal Glycosides,Protolinckiosides A – D,from the Starfish Protoreaster lincki

Four new steroidal glycosides, protolinckiosides A – D ( 1 – 4 , resp.), were isolated along with four previously known glycosides, 5 – 8 , from the MeOH/EtOH extract of the starfish Protoreaster lincki. The structures of 1 – 4 were elucidated by extensive NMR and ESI‐MS techniques as (3β,4β,5α,6β,7α,15α,16β,25S)‐4,6,7,8,15,16,26‐heptahydroxycholestan‐3‐yl 2‐O‐methyl‐β‐d ‐xylopyranoside ( 1 ), (3β,5α,6β,15α,24S)‐3,5,6,8,15‐pentahydroxycholestan‐24‐yl α‐l ‐arabinofuranoside ( 2 ), sodium (3β,6β,15α,16β,24R)‐29‐(β‐d ‐galactofuranosyloxy)‐6,8,16‐trihydroxy‐3‐[(2‐O‐methyl‐β‐d ‐xylopyranosyl)oxy]stigmast‐4‐en‐15‐yl sulfate ( 3 ), and sodium (3β,6β,15α,16β,22E,24R)‐28‐(β‐d ‐galactofuranosyloxy)‐6,8,16‐trihydroxy‐3‐[(2‐O‐methyl‐β‐d ‐xylopyranosyl)oxy]ergosta‐4,22‐dien‐15‐yl sulfate ( 4 ). The unsubstituted β‐d ‐galactofuranose residue at C(28) or C(29) of the side chains was found in starfish steroidal glycosides for the first time. Compounds 1 – 4 significantly decreased the intracellular reactive oxygen species (ROS) content in RAW 264.7 murine macrophages at induction by proinflammatory endotoxic lipopolysaccharide (LPS) from E. coli.     

Two New Chromone Glycosides from the Roots of Saposhnikovia divaricata

Five chromone glycosides were isolated from the water‐soluble portions of 70% EtOH extract of the roots of Saposhnikovia divaricata, including two new chromone glycosides 1 and 2 . The structures of the chromone glycosides were identified as (3′S)‐3′‐O‐β‐d ‐apiofuranosyl‐(1 → 6)‐β‐d ‐glucopyranosylhamaudol ( 1 ), (2′S)‐4′‐O‐β‐d ‐apiofuranosyl‐(1 → 6)‐β‐d ‐glucopyranosylvisamminol ( 2 ), 3′‐O‐glucopyranosylhamaudol ( 3 ), 4′‐O‐β‐d ‐glucopyranosylvisamminol ( 4 ), and 4′‐O‐β‐d ‐glucopyranosyl‐5‐O‐methylvisamminol ( 5 ) on the basis of extensive spectroscopic methods, and the absolute configurations of the new compounds were elucidated by the electronic circular dichroism (ECD) calculation and acid hydrolysis. The cytotoxic activities of the glycosides 1 – 5 against three human cancer cell lines (PC‐3, SK‐OV‐3, and H460) were evaluated. The result showed that compounds 1 – 5 had weak cytotoxic activities against the human cancer cell lines with IC₅₀ values in the range of 48.54 ± 0.80 – 94.25 ± 1.45 μm .     

Two new lignans and anti-HBV constituents from Illicium henryi

Two new lignans, dihydrodehydrodiconiferyl alcohol 9‐O‐β‐D ‐(3″‐O‐acetyl)‐xylopyranoside ( 1 ) and threo‐4,9,9′‐trihydroxy‐3,3′‐dimethoxy‐8‐O‐4′‐neolignan 7‐O‐α‐rhamnopyranoside ( 2 ) were isolated from Illicium henryi, together with ten known compounds, 3 – 12 . Their structures were elucidated by extensive spectroscopic analyses. The anti‐hepatitis B virus (anti‐HBV) activity of compounds 1 – 12 inhibiting HBV surface antigen (HBsAg) and HBV e antigen (HBeAg) secretion on Hep G2.2.15 cell line was evaluated. (−)‐Dihydrodehydrodiconiferyl alcohol ( 4 ) showed moderate inhibitory activity on both HBsAg and HBeAg secretion with IC₅₀ values of 0.06 and 0.53 mM , respectively.     

Piptadenin,a Novel 3,4‐Secooleanane Triterpene and Piptadenamide,a New Ceramide from the Stem Bark of Piptadeniastrum africanum (Hook.f.) Brenan

Piptadenin ( 1 ), a new triterpene along with piptadenamide ( 10 ), a new ceramide, have been isolated from the AcOEt‐soluble fraction of the MeOH extract of the stem bark of Piptadeniastrum africanum along with nine known compounds, 1‐O‐[(3β,22β)‐3,22‐dihydroxy‐28‐oxoolean‐12‐en‐28‐yl]‐β‐d ‐glucopyranose ( 2 ), 22β‐hydroxyoleanic acid ( 3 ), oleanic acid ( 4 ), lupeol ( 5 ), betulinic acid ( 6 ), 5α‐stigmasta‐7,22‐dien‐3β‐ol ( 7 ), 5α‐stigmasta‐7,22‐dien‐3‐one ( 8 ), (3β)‐stigmast‐5‐en‐3‐yl β‐d ‐glucopyranoside ( 9 ) and 2,3‐dihydroxypropyl hexacosanoate ( 11 ). Except for compound 11 , all the isolated compounds are reported for the first time from this plant. The structures of the isolated compounds were elucidated by spectroscopic data including 1D and 2D NMR. The pure compounds 1 – 11 were subjected to the pharmacological screening and compounds 2 , 5 – 7 and 9 exhibited potent urease inhibitory activity with IC₅₀ value of 25.8, 28.9, 30.1, 31.8 and 32.7 μm , respectively, whereas compound 1 showed moderate activity (IC₅₀ = 98.7 μm ). The potent urease inhibitory activity supplemented the previous literature reports and medicinal uses of this plant.     

Altered matrix polysaccharides in cell walls of pocket galls formed by an aphid on Distylium racemosum leaves

The present work reports the results of a study on the isolation and characterization of matrix polysaccharides in the cell walls of galls formed by an aphid (Neothoracaphis yanonis) on Distylium racemosum leaves. Cell walls were isolated from both healthy Distylium leaf and gall tissues and then extracted sequentially with cyclohexane‐trans‐1,2‐diaminetetra‐acetate (CDTA), Na₂CO₃, 1 m KOH, and 4 m KOH. The amount of pectin solubilized from gall cell walls was approximately 2.6‐fold higher than the pectin solubilized from leaf cell walls, whereas the amount of hemicellulose solubilized from gall cell walls was 1.4‐fold higher than that from normal leaf cell walls. When the polysaccharides were fractionated by anion‐exchange chromatography, considerable increases in arabinose and galactose were observed in CDTA‐soluble pectic polymer (fraction PI‐1) from gall cell walls, whereas the gall cell walls had less xylose in 1 m KOH‐soluble hemicellulosic polymers (fractions HI‐2, HI‐3, and HI‐4) than did the cell walls from the healthy leaf. The hemicellulosic polymers of the gall cell walls exhibited distinctly different patterns of molecular mass, compared with the healthy leaf cell walls. These results suggest that an extensive change occurs in the matrix polysaccharide structure of the cell walls of Distylium galls formed by an aphid. In addition, many glycosylhydrolase activities were detected in the protein fraction solubilized with strong saline solution from the gall cell walls, and the activities of β‐galactosidase, β‐xylosidase and α‐l ‐arabinofuranosidase were considerably increased under gall formation.     

Simenoside A,a New Triterpenoid Saponin from Gypsophila simonii Hub.‐Mor.

Saponins are amphiphilic glycoconjugates which give soap‐like foams in H₂O. A new triterpenoid saponin, simenoside A ( 1 ), based on gypsogenin aglycone, and the known saponin 2 were isolated from Gypsophila simonii Hub.‐Mor. The structure of the new saponin was elucidated as 3‐O‐β‐D ‐galactopyranosyl‐(1→2)‐[β‐D ‐xylopyranosyl‐(1→3)]‐β‐D ‐glucuronopyranosylgypsogenin 28‐O‐β‐D ‐glucopyranosyl‐(1→3)‐[β‐D ‐glucopyranosyl‐(1→2)‐β‐D ‐xylopyranosyl‐(1→4)]‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐fucopyranosyl ester on the basis of extensive spectral analyses and chemical evidence. Saponins 1 and 2 were isolated from G. simonii for the first time.     

Cytotoxic Mannopyranosides of Indole Alkaloids from Zanthoxylum nitidum

Three new mannopyranosides of indole alkaloids, methyl 7‐(β‐D ‐mannopyranosyloxy)‐1H‐indole‐2‐carboxylate ( 1 ), methyl 7‐[(3‐O‐acetyl‐β‐D ‐mannopyranosyl)oxy]‐1H‐indole‐2‐carboxylate ( 2 ), and 2‐methyl‐1H‐indol‐7‐yl β‐D ‐mannopyranoside ( 3 ), were isolated from an EtOH extract of the roots of Zanthoxylum nitidum. Their structures were identified as new compounds on the basis of the spectroscopic analyses. Bioactivity evaluation revealed that these alkaloids possess significant cytotoxicities against all the tested tumor cell lines with IC₅₀ values of less than 30 μM .     

N‐acetyl‐L‐cysteine inhibits bleomycin induced apoptosis in malignant testicular germ cell tumors

Antioxidants may prevent apoptosis of cancer cells via inhibiting reactive oxygen species (ROS). However, to date no study has been carried out to elucidate the effects of strong antioxidant N‐acetylcysteine (NAC) on Bleomycin induced apoptosis in human testicular cancer (NTERA‐2, NT2) cells. For this reason, we studied the effects of Bleomycin and NAC alone and in combination on apoptotic signaling pathways in NT2 cell line. We determined the cytotoxic effect of bleomycin on NT2 cells and measured apoptosis markers such as Caspase‐3, ‐8, ‐9 activities and Bcl‐2, Bax, Cyt‐c, Annexin V‐FTIC and PI levels in NT2 cells incubated with different agents for 24 h. Early apoptosis was determined using FACS assay. We found half of the lethal dose (LD₅₀) of Bleomycin on NT2 cell viability as 400, 100, and 20 µg/ml after incubations for 24, 48, and 72 h, respectively. Incubation with bleomycin (LD₅₀) and H₂O₂ for 24 h increased Caspase‐3, ‐8, ‐9 activities, Cyt‐c and Bax levels and decreased Bcl‐2 levels. The concurrent incubation of NT2 cells with bleomycin/H₂O₂ and NAC (5 mM) for 24 h abolished bleomycin/H₂O₂‐dependent increases in Caspase‐3, ‐8, ‐9 activities, Bax and Cyt‐c levels and bleomycin/H₂O₂‐dependent decrease in Bcl‐2 level. Our results indicate that bleomycin/H₂O₂ induce apoptosis in NT2 cells by activating mitochondrial pathway of apoptosis, while NAC diminishes bleomycin/H₂O₂ induced apoptosis. We conclude that NAC has antagonistic effects on Bleomycin‐induced apoptosis in NT2 cells and causes resistance to apoptosis which is not a desired effect in eliminating cancer cells. J. Cell. Biochem. 114: 1685–1694, 2013. © 2013 Wiley Periodicals, Inc.     

Dodecyl α‐L‐Rhamnopyranosyl‐(1→2)‐β‐D‐fucopyranoside Derivatives from the Glandular Trichome Exudate of Erodium pelargoniflorum

Chemical investigation of the glandular trichome exudate of Erodium pelargoniflorum (Geraniaceae) led to the isolation of two dodecyl disaccharide derivatives, named pelargoside A1 and pelargoside B1 ( 1 and 2 , resp.). The structures of 1 and 2 were determined as dodecyl 4‐O‐acetyl‐α‐L ‐rhamnopyranosyl‐(1→2)‐4‐O‐acetyl‐β‐D ‐fucopyranoside and dodecyl 3,4‐di‐O‐acetyl‐α‐L ‐rhamnopyranosyl‐(1→2)‐4‐O‐acetyl‐β‐D ‐fucopyranoside, respectively, by spectroscopic studies, including 2D‐NMR, and chemical transformations. In addition, undecyl, tridecyl, and tetradecyl homologs of 1 and 2 , named pelargosides A2–A4 and pelargosides B2–B4, were also characterized as minor constituents of the exudate.     

Cytotoxic Oleanane‐Type Saponins from the Leaves of Albizia anthelmintica Brongn.

Two new oleanane‐type saponins: β‐d ‐xylopyranosyl‐(1 → 4)‐6‐deoxy‐α‐l ‐mannopyranosyl‐(1 → 2)‐1‐O‐{(3β)‐28‐oxo‐3‐[(2‐O‐β‐d ‐xylopyranosyl‐β‐d ‐glucopyranosyl)oxy]olean‐12‐en‐28‐yl}‐β‐d ‐glucopyranose ( 1 ) and 1‐O‐[(3β)‐28‐oxo‐3‐{[β‐d ‐xylopyranosyl‐(1 → 2)‐α‐l ‐arabinopyranosyl‐(1 → 6)‐2‐acetamido‐2‐deoxy‐β‐d ‐glucopyranosyl]oxy}olean‐12‐en‐28‐yl]β‐d ‐glucopyranose ( 2 ), along with two known saponins: (3β)‐3‐[(β‐d ‐Glucopyranosyl‐(1 → 2)‐β‐d ‐glucopyranosyl)oxy]olean‐12‐en‐28‐oic acid ( 3 ) and (3β)‐3‐{[α‐l ‐arabinopyranosyl‐(1 → 6)‐[β‐d ‐glucopyranosyl‐(1 → 2)]‐β‐d ‐glucopyranosyl]oxy}olean‐12‐en‐28‐oic acid ( 4 ) were isolated from the acetone‐insoluble fraction obtained from the 80% aqueous MeOH extract of Albizia anthelmintica Brongn . leaves. Their structures were identified using different NMR experiments including: ¹H‐ and ¹³C‐NMR, HSQC, HMBC and ¹H,¹H‐COSY, together with HR‐ESI‐MS/MS, as well as by acid hydrolysis. The four isolated saponins and the fractions of the extract exhibited cytotoxic activity against HepG‐2 and HCT‐116 cell lines. Compound 2 showed the most potent cytotoxic activity among the other tested compounds against the HepG2 cell line with an IC₅₀ value of 3.60μm . Whereas, compound 1 showed the most potent cytotoxic effect with an IC₅₀ value of 4.75μm on HCT‐116 cells.     

Crystallographic and mutational analyses of cystathionine β‐synthase in the H2S‐synthetic gene cluster in Lactobacillus plantarum

Cystathionine β‐synthase (CBS) catalyzes the formation of l ‐cystathionine from l ‐serine and l ‐homocysteine. The resulting l ‐cystathionine is decomposed into l ‐cysteine, ammonia, and α‐ketobutylic acid by cystathionine γ‐lyase (CGL). This reverse transsulfuration pathway, which is catalyzed by both enzymes, mainly occurs in eukaryotic cells. The eukaryotic CBS and CGL have recently been recognized as major physiological enzymes for the generation of hydrogen sulfide (H₂S). In some bacteria, including the plant‐derived lactic acid bacterium Lactobacillus plantarum, the CBS‐ and CGL‐encoding genes form a cluster in their genomes. Inactivation of these enzymes has been reported to suppress H₂S production in bacteria; interestingly, it has been shown that H₂S suppression increases their susceptibility to various antibiotics. In the present study, we characterized the enzymatic properties of the L. plantarum CBS, whose amino acid sequence displays a similarity with those of O‐acetyl‐l ‐serine sulfhydrylase (OASS) that catalyzes the generation of l ‐cysteine from O‐acetyl‐l ‐serine (l ‐OAS) and H₂S. The L. plantarum CBS shows l ‐OAS‐ and l ‐cysteine‐dependent CBS activities together with OASS activity. Especially, it catalyzes the formation of H₂S in the presence of l ‐cysteine and l ‐homocysteine, together with the formation of l ‐cystathionine. The high affinity toward l ‐cysteine as a first substrate and tendency to use l ‐homocysteine as a second substrate might be associated with its enzymatic ability to generate H₂S. Crystallographic and mutational analyses of CBS indicate that the Ala70 and Glu223 residues at the substrate binding pocket are important for the H₂S‐generating activity.     

Phytochemical Analysis,Biological Activity,and Secretory Structures of Stachys annua (L.) L. subsp. annua (Lamiaceae) from Central Italy

Stachys annua subsp. annua, well‐known in central Italy as ‘stregona annuale’, is an annual, small, slightly‐scented herb, commonly found in fields and uncultivated areas in almost all regions of Italy. In folk medicine, its aerial parts were used as anti‐catarrhal, febrifuge, tonic, and vulnerary. In the present work, the chemical composition of the flowering aerial parts was studied. The hydrodistilled volatile oil, analysed by GC/MS, showed sesquiterpenoids as the major fraction (42.5%); phytol (9.8%), germacrene D (9.2%), and spathulenol (8.5%) were the most abundant constituents. The volatile oil was assayed for antioxidant and cytotoxic activity by DPPH, ABTS, FRAP, and MTT methods. The cytotoxicity results against HCT116, A375, and MDA‐MB 231 human tumor cell lines were significant, with IC₅₀ values of 23.5, 37.2, and 41.5 μg/ml, respectively, whereas the antioxidant power was negligible. The EtOH extract was composed mainly of three glycosidic flavonoids, namely 7‐{[2‐O‐(6‐O‐acetyl‐β‐D ‐allopyranosyl)‐β‐D ‐glucopyranosyl]oxy}‐5,8‐dihydroxy‐2‐(4‐methoxyphenyl)‐4H‐1‐benzopyran‐4‐one ( 1 ), 7‐{[6‐O‐acetyl‐2‐O‐(6‐O‐acetyl‐β‐D ‐allopyranosyl)‐β‐D ‐glucopyranosyl]oxy}‐2‐(3,4‐dihydroxyphenyl)‐5,8‐dihydroxy‐4H‐1‐benzopyran‐4‐one ( 2 ), and 7‐{[6‐O‐acetyl‐2‐O‐(β‐D ‐allopyranosyl)‐β‐D ‐glucopyranosyl]oxy}‐2‐(3‐hydroxy‐4‐methoxyphenyl)‐5,8‐dihydroxy‐4H‐1‐benzopyran‐4‐one ( 3 ). On the contrary, iridoids, considered chemotaxonomic markers of the genus Stachys, were absent in this species. Finally, the morphological and histochemical survey showed that glandular trichomes were composed of two main types, i.e. peltate type A and capitate types B and C giving positive response for both lipids and polyphenols.     

Triterpene Glucosides from the Leaves of Aralia elata and Their Cytotoxic Activities

Three new triterpene glucosides, named congmuyenosides C–E ( 1 – 3 , resp.), along with four known ones, were isolated from an EtOH extract of Aralia elata (Miq .) Seem . leaves. The structures of the new compounds were identified as 3‐O‐{β‐D ‐glucopyranosyl‐(1→3)‐β‐D ‐glucopyranosyl‐(1→3)‐[β‐D ‐glucopyranosyl‐(1→2)]‐β‐D ‐glucopyranosyl}caulophyllogenin ( 1 ), 3‐O‐{β‐D ‐glucopyranosyl‐(1→3)‐β‐D ‐glucopyranosyl‐(1→3)‐[β‐D ‐glucopyranosyl‐(1→2)]‐β‐D ‐glucopyranosyl}hederagenin 28‐O‐β‐D ‐glucopyranosyl ester ( 2 ), 3‐O‐{β‐D ‐glucopyranosyl‐(1→3)‐β‐D ‐glucopyranosyl‐(1→3)‐[β‐D ‐glucopyranosyl‐(1→2)]‐β‐D ‐glucopyranosyl}echinocystic acid 28‐O‐β‐D ‐glucopyranosyl ester ( 3 ) on the basis of spectral analyses, including MS, ¹H‐NMR, ¹³C‐NMR, DEPT, HSQC, HMBC, NOESY, and HSQC‐TOCSY experiments. All isolates obtained were evaluated for their cytotoxic activities against three human tumor cell lines (HepG2, SKOV3, and A549). Compound 3 showed significant cytotoxicity against A549 cell line (IC₅₀ 9.9±1.5 μM ).