Acetylated allose-containing flavonoid glucosides from Stachys anisochila

In continuation of our chemosystematic study of Stachys (Labiatae) we have isolated the previously reported isoscutellarein 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-β-D-glucopyranoside] (1) and 3′-hydroxy-4′-O-methylisoscutellarein 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-β-D-glucopyranoside] (4) and four new allose-containing flavonoid glycosides from S. anisochila. The new glycosides are hypolaetin 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-β-D-glucopyranside] (6) as well as the three corresponding diacetyl analogues of 1, 4 and 6, isoscutellarein 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-6″-O-acetyl-β-D-glucopyranoside], 3′-hydroxy-4′-O-methylisoscutellarein 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-6″-O-acetyl-β-D-glucopyranoside] and hypolaetin 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-6″-O-acetyl-β-D-glucopyranoside]. Extensive two-dimensional NMR studies (proton-carbon correlations, COSY experiments) allowed assignment of all ¹H NMR sugar signals and a correction of the ¹³C NMR signal assignments for C-2 and C-3 of the allose.     

(2S)-Prenylflavanones and taraxerane triterpenoids from Mallotus mollissimus

Three prenylflavanones, (2S)-5,7-dihydroxy-4′-methoxy-8-(3″,3″-dimethylallyl)flavanone (3), (2S)-5,4′-dihydroxy-7-methoxy-6-(3″,3″-dimethylallyl)flavanone (6), 8-prenylnaringenin (11), and a new epimeric pair (2″S/2″R)-(2S)-5,7-dihydroxy-4′-methoxy-6-(2″-hydroxy-3″-methylbut-3″-enyl)flavanones (4a/4b) were isolated together with taraxerone, taraxerol, epitaraxerol, β-sitosterol, oleanolic acid, 1-O-docosanoyl glycerol, apigenin, and apigenin 7-O-β-D-glucopyranoside from the MeOH extract of the leaves of Mallotus mollissimus. The structures of the isolated compounds were determined on the basis of 1D/2D NMR and HR-MS spectroscopic data; the 2S configuration of the prenylflavanones 3, 4, and 6 was deduced from CD spectroscopic data. The presence of three taraxerane triterpenoids reinforces the inclusion of M. mollissimus (syn. Croton mollissimus) in Mallotus genus. Among species of Mallotus the occurrence of the (2S)-prenylflavanones 3, 4, and 6 is confined to M. mollissimus.     

New aromatic compounds from the rhizomes of Homalomena occulta

Three new aromatic compounds, identified as 1-(3′,4′-methylenedioxy-phenyl)-10-(3″-hydroxyphenyl)-decane (1), 1-(3′,4′-methylenedioxy-phenyl)-12-(3″-hydroxyphenyl)-dodecane (2), and 1-(3′,4′-methylenedioxy-phenyl)-12-(3″-hydroxyphenyl)-6Z-dodecylene (3), along with six known compounds (4–9) were isolated from the 95% EtOH extract of Homalomena occulta. Their structures were elucidated by chemical and spectral methods Compounds 4–9 were isolated for the first time from this plant. Compounds 1–3 exhibited inhibitory activity against BACE1, with IC₅₀ values of 0.82–1.09 μmol/L.     

New prenylated isoflavones and a prenylated dihydroflavonol from Millettia pachycarpa

Extraction of Millettia pachycarpa Benth. gave 5,7,4′-trihydroxy-6,8-diprenylisoflavone (1a), 5,7,4′-trihydroxy-6,3′-diprenylisoflavone (2a), 5,7,3′,4′-tetrahydroxy-6,8-diprenylisoflavone (3a) and (2R, 3R)-5,4′-dihydroxy-8-prenyl-6″,6″-dimethylpyrano[2″,3″: 7,6]-dihydroflavonol (4a) whose structures were established by chemical transformations and spectroscopic means. Pectolinarigenin and salvigenin were isolated from Buddleia macrostachya Benth.     

Two new diphenyl ethers from Acanthopanax senticosus (Rupr. & Maxim.) Harms with PTP1B inhibitory activity

Bioassay-guided fractionation of an EtOAc-soluble extract of Acanthopanax senticosus (Rupr. & Maxim.) Harms yielded two new diphenyl ethers, 3-[3′-methoxy-4′-(4″-formyl-2″,6″-dimethoxy-phenoxy)-phenyl]-propenal (1) and 3-[3′,5′-dihydroxy-4′-(4″-hydroxymethyl-3″,5″-dimethoxy-phenoxy)-phenyl]-propenal (2), along with eight other known compounds (3–10). The structures of these new ethers were elucidated with spectroscopic and physico-chemical analyses. All of the isolates were evaluated for their in vitro inhibitory activity against PTP1B, VHR and PP1. The new compounds (1 and 2) inhibited PTP1B with IC₅₀ values ranging from 9.2 ± 1.4 to 12.6 ± 1.2 μM.     

Flavonoid diversification in different leaf compartments of Primula auricula (Primulaceae)

Populations of Primula auricula L. subsp. auricula from Austrian Alps were studied for flavonoid composition of both farinose exudates and tissue of leaves. The leaf exudate yielded Primula-type flavones, such as unsubstituted flavone and its derivatives, while tissue flavonoids largely consisted of flavonol 3-O-glycosides, based upon kaempferol (3, 4) and isorhamnetin (5–7). Kaempferol 3-O-(2″-O-β-xylopyranosyl-[6″-O-β-xylopyranosyl]-β-glucopyranoside) (3) and isorhamnetin 3-O-(2″-O-β-xylopyranosyl-[6″-O-β-xylopyranosyl]-β-glucopyranoside) (6) are newly reported as natural compounds. Remarkably, two Primula type flavones were also detected in tissues, namely 3′-hydroxyflavone 3′-O-β-glucoside (1) and 3′,4′-dihydroxyflavone 4′-O-β-glucoside (2), of which (1) is reported here for the first time as natural product. All structures were unambiguously identified by NMR and MS data. Earlier reports on the occurrence of 7,2′-dihydroxyflavone 7-O-glucoside (macrophylloside) in this species could not be confirmed. This structure was now shown to correspond to 3′,4′-dihydroxyflavone 4′-O-glucoside (2) by comparison of NMR data. Observed exudate variations might be specific for geographically separated populations. The structural diversification between tissue and exudate flavonoids is assumed to be indicative for different ecological roles in planta.     

Chemical modification of the nonreducing,terminal group of maltotriose

O-α-d-Galactopyranosyl-(1→4)-O-α-d-glucopyranosyl-(1→4)-d-glucopyranose (12) was prepared by inversion of configuration at C-4″ of 2,3,2′,3′,6′,2″,3″-hepta-O-acetyl-1,6-anhydro-4″,6″-di-O-methylsulfonyl-β-maltotriose (7), followed by O-deacylation, acetylation, acetolysis, and de-O-acetylation. The intermediate 7 was obtained by treatment of 1,6-anhydro-β-maltotriose (2) with benzal chloride in pyridine, followed by acetylation, removal of the benzylidene group, and methane-sulfonylation. Selective tritylation of 2 and subsequent acetylation afforded 2,3,2′,3′,6′,2″,3″,4″-octa-O-acetyl-1,6-anhydro-6″-O-trityl-β-maltotriose (6), which was O-detritylated and p-toluenesulfonylated to give 2,3,2′,3′,6′,2″,3″,4″-octa-O-acetyl-1,6-anhydro-6″-O-p-tolylsulfonyl-β-maltotriose (13). Nucleophilic displacement of 13 with thioacetate, iodide, bromide, chloride, and azide ions gave 6″-S-acetyl- (14), 6″-iodo- (15), 6″-bromo- (16), 6″-chloro- (19), and 6″-azido- (20) 1,6-anhydro-β-maltotriose octaacetates, respectively. 6″Deoxy- (18) and 6″-acetamido-6″-deoxy (21) derivatives of 1,6-anhydro-β-maltotriose decaacetates were also prepared from 15 and 16, and 20, respectively. Acetolysis of 14, 15, 16, 18, 19, and 21 afforded 1,2,3,6,2′,3′,6′,2″,3″,4″-deca-O-acetyl-6″-S-acetyl (22), -6″-iodo (23), -6″-bromo (24), -6″-deoxy (25), -6″-chloro (26), and -6″-acetamido-6′-deoxy (27) derivatives of α-maltotriose, respectively. O-Deacetylation of 24, 25, and 26 furnished 6″-bromo-(28), 6″-deoxy- (29), and 6″-chloro- (30) maltotrioses, respectively, which on acetylation gave the corresponding β-decaacetates.     

2-[(4″-Hydroxy-3′-methoxy)-phenoxy]-4-(4″-hydroxy-3″-methoxy-phenyl)-8-hydroxy-6-oxo-3-oxabicylo[3.3.0]-7-octene: unusual product of the soybean lipoxygenase-catalyzed oxygenation of curcumin

Racemic (1SR,2SR,4SR,5SR)-2-[(4′-hydroxy-3′-methoxy)-phenoxy]-4-(4″-hydroxy-3″-methoxy-phenyl)-8-hydroxy-6-oxo-3-oxabicyclo[3.3.0]-7-octene (2, C₂₁H₂₀O₈) was isolated as major product of soybean lipoxygenase action on curcumin (1, C₂₁H₂₀O₆). The structure of 2 was elucidated by HPLC-APCI-MS and tandem MS, ¹H, ¹³C, DEPT, H,H-COSY, H,C-HMQC, H,C-HMBC and phase sensitive 2D NOESY NMR techniques. For kinetic studies the rate of substrate degradation was followed spectrophotometrically at 430 nm, and the rate of oxygen consumption was measured polarographically. As evaluated by both methods, K_m for 1 was about four times higher than that obtained for linoleic acid (as the best substrate for soybean lipoxygenase); V_max was reduced five-fold. Lipoxygenase-mediated oxygenation of 1 was confirmed by the following criteria: (i) curcumin did not react with inactivated lipoxygenase; (ii) the enzymatic reaction was strongly inhibited by inhibitors such as BHA, deferoxamine and HgCl₂; (iii) oxygen consumption (measured polarographically) and curcumin degradation (measured photometrically) were shown to occur simultaneously at a ratio of 0.8 to 1, suggesting insertion of oxygen into 1 by lipoxygenase; (iv) molecular mass estimation by APCI-MS showed a shift of 32 in molecular mass from 1 (M_r 368) to 2 (M_r 400) being equivalent to an insertion of dioxygen. Curcumin meets none of the common features for lipoxygenase substrates and, therefore, may represent a new type of substrates for this enzyme.     

Distribution of acetylenic thiophenes in the pectidinae

The distribution and quantitative significance of biosynthetically related di- and ter-thiophenes from 27 species representing seven genera of the Pectidinae (Heliantheae) was investigated by reverse-phase HPLC. Adenophyllum, Chrysactinia and Nicolletia, three previously unstudied genera, were found to contain thiophenes for the first time. Four derivatives, 5-(4-hydroxy-1-butenyl)-2,2′-bithiophene (1), 5-(4-acetoxy-1-butenyl)-2,2′-bithiophene (2), 5-(3-buten-1-ynyl)-2,2′-bithiophene (3) and 2,2′:5′,2″-terthiophene (4) were common constituents in most species of Adenophyllum, Chrysactinia, Dyssodia, Hymenatherum, Nicolletia and Porophyllum. One additional compound, 5-methyl-2,2′:5′,2″-terthiophene (5), was also present in extracts of Adenophyllum, Dyssodia and Hymenatherum, but was not detected in any other genus. Acetylenic thiophenes were not found in any of the 18 species of Pectis examined.     

Two new anti-HBV lignans from Herpetospermum caudigerum

Two new lignans, named (+)-(7′S, 7″S, 8′R, 8″R)-4, 4′, 4″-trihydroxy-3, 5′, 3″-trimethoxy-7-oxo-8-ene [8-3′, 7′-O-9″, 8′-8″, 9′-O-7″] lignoid (1) and (1S)-4-Hydroxy-3-[2-(4-hydroxy-3-methoxy-phenyl)-1-hydroxymethyl-2-oxo-ethyl]-5-methoxy-benzaldehyde (2), along with five known (3–7) ones, have been isolated from the 95% ethanol extract of the seeds of Herpetospermum caudigerum Wall. The structures of the new compounds, including the absolute configurations, were elucidated by spectroscopic and CD analysis. Compounds 1, 2, and 7 displayed inhibitory activities on HBsAg secretion with IC₅₀ values of 20.5, 0.34, and 4.89 μM, while 1, 2, and 7 displayed inhibitory activities on HBeAg secretion with IC₅₀ values of 3.54, 4.83 × 10⁻⁴, and 8.02 μM, and cytotoxicity on HepG 2.2.15 cells with CC₅₀ values of 12.7, 2.96 × 10⁵, and 11.4 μM, respectively.     

Microbial metabolism of cannflavin A and B isolated from Cannabis sativa

Microbial metabolism of cannflavin A (1) and B (2), two biologically active flavonoids isolated from Cannabis sativa L., produced five metabolites (3–7). Incubation of 1 and 2 with Mucor ramannianus (ATCC 9628) and Beauveria bassiana (ATCC 13144), respectively, yielded 6″S,7″-dihydroxycannflavin A (3), 6″S,7″-dihydroxycannflavin A 7-sulfate (4) and 6″S,7″-dihydroxycannflavin A 4′-O-α-l-rhamnopyranoside (5), and cannflavin B 7-O-β-d-4?-O-methylglucopyranoside (6) and cannflavin B 7-sulfate (7), respectively. All compounds were evaluated for antimicrobial and antiprotozoal activity.     

Xanthonolignoids from Kielmeyera and Caraipa species—13C NMR spectroscopy of xanthones

Kielcorin and the cadensins A and B, isolated respectively from Kielmeyera coriacea and Caraipa densiflora (Guttiferae), were shown to be xanthonolignoids. The structure of (5S,6S)-6(or 5)-hydroxymethyl-5(or 6)-(4″-hydroxy-3″-methoxyphenyl)-2,3:3′,4′-(2′-methoxyxanthono)-1,4-dioxane was proposed for kielcorin by analysis of high resolution MS and PMR spectra. The carbon shifts of xanthone were assigned and used in the ¹³C NMR spectral confirmation of the proposed structure.     

Sesquiterpenoids and lignans from the fruits of Illicium simonsii Maxim

Twenty-two known compounds were isolated from the 95% alcohol extract of the fruits of Illicium simonsii Maxim, including seven sesquiterpenoids (16–22) and fifteen lignans (1–15). In the present research, compounds 3 ((7S,8R,8′S)-3,3′-dimethoxy-4,4′,9-trihydroxy-7,9′-epoxylignan-7′-one), 4 ((−)-(7′S,8S,8′R)-4,4′-dihydroxy-3,3′,5,5′-tetramethoxy-7′,9-epoxylignan-9′-ol-7-one), 5 ((+)-8-hydroxypinoresinol), 6 ((+)-8-hydroxymedioresinol), 8 ((2R,3R)-2β-(4″-hydroxy-3″-methoxybenzyl)-3α-(4′-hydroxy-3′-methoxybenzyl)-γ-butyrolactone 2-O-(β-D-glucopyranoside), 12 ((+)-8-methoxyisolariciresinol), 13 (α-conidendrin), 14 (boehmenan) and 15 (7R,8R,7′E-7′,8′-didehydro-4,7,9,9′- tetrahydroxy-3-methoxy-8-O-4′-neolignan) were reported from the Illicium genus for the first time, and compounds 1 (simulanol), 7 ((+)-secoisolariciresinol monoglucoside), 10 ((+)-9-O-β-D-glucopyranosyl lyoniresinol), 11 ((+)-isolariciresinol), 18 (neoanisatin), 19 (veranisatin A), 20 (4,5-d₂-8′-oxo-dihydrophaseic acid) and 22 (Oligandrumin A) were firstly isolated from the plant. Their structures were elucidated on the basis of NMR spectroscopic and mass spectrometric data. Moreover, the chemotaxonomic significance of the isolated compounds is discussed.     

Toddasin,a new dimeric coumarin from Toddalia asiatica

A new dimeric coumarin, named toddasin and possessing a cyclohexene ring with a vinylic side-chain interposed between the two coumarin moieties has been isolated from the roots of Toddalia asiatica. It has been characterized as (E)-8,8′-[1″,4″-dimethyl-3″ -cyclohexen-1″,2″-ylene vinylene]-bis-[5,7-dimethoxycoumarin] (1). The proposed structure is supported by the mass fragmentation of its dihydro derivative (2).     

Unusual lipids and acylglucosylsterols from the roots of Livistona chinensis

A 70% ethanol extract from the roots of Livistona chinensis has been investigated, led to the isolation of 18 compounds, including two new 6′-O-acyl-β-d-glucosyl-β-sitosterols, 6′-O-(2″-hydroxyheptadecanoyl)-β-d-glucosyl-β-sitosterol (1) and 6′-O-(icosa-9″Z,12″Z-dienoyl)-β-d-glucosyl-β-sitosterol (2), two new keto esters, ethyl 16-(dodeca-4″′Z,7″′Z-dienyl)-29-oxo-15-(tetradeca-5″Z,8″Z,11″Z-trienyl) triacontanoate (7), and 16-hydroxy-8-oxohexadecyl tetradecanoate (9), a new unsaturated fatty acid, tetracosa-(11Z,14Z,18Z)-trienoic acid (8), as well as a new fatty alcohol, 10-decylnonadecane-1,19-diol (10). The structures of new compounds were elucidated, based on spectroscopic and chemical methods. The antiproliferative activity against four human tumor cell lines (K562, HL-60, HepG2, and CNE-1) was evaluated. Four compounds (1–3, 5) showed potent antiproliferative effects with the IC₅₀ of 10–100 μM. To our knowledge, this is the first report of the occurrence of 6′-O-acyl-β-d-glucosyl-β-sitosterol and 3-O-acyl-β-sitosterol in the genus Livistona. Keto fatty acids and their esters are also rare in higher plant.     

Dihydrochalcone glucosides and antioxidant activity from the roots of Anneslea fragrans var. lanceolata

Bioassay-guided fractionation of the roots of Anneslea fragrans var. lanceolata led to the isolation of four dihydrochalcone glucosides, davidigenin-2′-O-(6″-O-4″′-hydroxybenzoyl)-β-glucoside (1), davidigenin-2′-O-(2″-O-4″′-hydroxybenzoyl)-β-glucoside (2), davidigenin-2′-O-(3″-O-4″′-hydroxybenzoyl)-β-glucoside (3), and davidigenin-2′-O-(6″-O-syringoyl)-β-glucoside (4), and 13 known compounds. The structures were identified by means of spectroscopic analysis. Davidigenin-2′-O-(6″-O-syringoyl)-β-glucoside (4), 1-O-3,4-dimethoxy-5-hydroxyphenyl-6-O-(3,5-di-O-methylgalloyl)-β-glucopyranoside (5), lyoniresinol (10), and syringic acid (13) showed ABTS [2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)] cation radical scavenging activity, with SC₅₀ values of 52.6 ± 5.5, 26.0 ± 0.7, 6.0 ± 0.2, and 27.5 ± 0.6 μg/mL in 20 min, respectively. Lyoniresinol (10), isofraxidin (12), and syringic acid (13) also showed DPPH [1,1-diphenyl-2-picrylhydrazyl] radical scavenging activity, with SC₅₀ values of 8.4 ± 1.8, 51.6 ± 2.2, and 4.3 ± 0.7 μg/mL in 30 min, respectively.     

Four new coumarins from the roots of Peucedanum arenarium

The roots of Peucedanum arenarium var. arenarium revealed the presence of 4 new natural coumarins. By spectral data their structures were elucidated as follows: peuarin, 3′-angeloyl-4′-methylisokhellactone; peuchlorin, 3′-angeloyl-4′-(2″-hydroxy-2″-methyl-3″-chloro)-butyroylisokhellactone; peuchlorinin, 3′-(2″-methylepoxy)-butyroyl-4′-(2″-hydroxy-2″-methyl-3″-chloro)-butyroylisokhellactone; peucloridin 3′,4′-di-(2″-hydroxy-2″-methyl-3″-chloro)-butyroylisokhellactone.     

Neolignans of Virola carinata bark

Four neolignans, dehydrodieugenol, its monomethylether, carinatone and carinatin have been isolated from the hexane fraction of the bark of Virola carinata. Three new neolignans were separated from the chloroform fraction and examined by spectroscopy and chemical reactions. Their structures were determined as (2S, 3S)-5-allyl- 7-methoxy-3-hydroxymethyl-2-(3′,4′-dimethoxyphenyl)-2,3-dihydrobenzofuran, (2S)- 1-(3′,4′-dimethoxyphenyl)-2-(3″-allyl-5″-methoxy-6″-hydroxyphenyl)propanone(1) ol(3), (1S,2S)-1-(3′,4′-dimethoxyphenyl)-2-(3″-allyl-5″-methoxy-6″-hydroxyphenyl) propanol(1) and called dihydrocarinatinol, carinatonol and carinatol, respectively.     

The promiscuous ectonucleotidase NPP1: molecular insights into substrate binding and hydrolysis

Nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) represents the main subtype of the NPP family of nucleotide hydrolyzing enzymes. The ecto-enzyme hydrolyzes structurally diverse substrates and has recently been proposed as a drug target for immuno-oncology. To get more insights into the nature of the promiscuity of NPP1, we investigated its substrate preferences employing a broad range of natural nucleotides including ATP, UTP, diadenosine tetraphosphate (AP₄A), cAMP, and cyclic guanosine-(2′,5′)-monophosphate-adenosine-(3″,5″)-monophosphate (2′,3″-cGAMP), as well as the artificial substrate p-nitrophenyl 5′-thymidine monophosphate (p-Nph-5′-TMP). Despite their diverse structures, all substrates were converted to nucleoside 5′-monophosphates; 2′,3″-cGAMP yielded exclusively the nucleoside 5′-monophosphates AMP and GMP. In contrast, 3′,3″-bridged cyclic dinucleotides were not hydrolyzed. ATP was the most efficiently hydrolyzed substrate of NPP1, followed by AP₄A and 2′,3″-cGAMP. UTP, cAMP and p-Nph-5′-TMP were much poorer substrates. A homology model of the human NPP1 was built based on the X-ray structure of its mouse orthologue. Docking studies were performed based on previously published mutagenesis data to rationalize the interactions of the different substrates and to explain the enzyme's preferences. The results provide an improved understanding of the interactions of NPP1 with its diverse substrates and will contribute to the validation of NPP1 as a drug target.     

Studies on synthesis and activation mechanism of mitomycin dimers connected by 1,2-dithiolane and diol linkers

We report the synthetic and mechanistic studies on a new cyclic disulfide mitomycin dimer, 7-N,7′-N′-(1″,2″-dithiolanyl-3″,5″-dimethylenyl)bismitomycin C (8), and a diol mitomycin dimer, 7-N,7′-N′-(2″,4″-dihydroxy-1″,5″-pentanediyl)bismitomycin C (9). Mitomycin 8 is a dimer connected by a 1,2-dithiolane (a five-membered cyclic disulfide) linker, and was specifically designed to undergo nucleophilic activation and double DNA alkylations leading to efficient production of DNA interstrand cross-link (DNA ISC) adducts. Disulfide cleavage in 8 would generate two thiol groups that could serve as probes to activate two mitomycin rings. At first, the target mitomycin 8 was synthesized using mitomycin A (1) and the key intermediate, cyclic disulfide (10), which was prepared through a seven-step synthetic sequence. Diol mitomycin 9 was also synthesized from 1 and diamine salt 13. Next, kinetic studies using solvolysis reaction revealed that the activation rates of 8 were much higher than those of 9 and mitomycin C (2) under nucleophilic conditions provided by Et₃P presumably due to the presence of a cyclic disulfide unit in 8. These findings led us to propose a nucleophilic activation pathway for 8. Then, DNA ISC experiments further revealed that the levels of DNA ISC caused by 8 in the presence of Et₃P were much higher (97%) than those by 9 (5%) and 2 (4%). More importantly, mitomycin 8 underwent much faster activation and produced slightly higher levels of DNA ISC than the previously reported mitomycins 5–7. Overall, we concluded that 8 was highly efficient for both nucleophilic activation and corresponding DNA ISC formation, and that this differentiation came from the crucial function of the cyclic disulfide unit in 8.