Lucidafuranocoumarins B and C from the twigs of Feroniella lucida: Absolute configurations of lucidafuranocoumarin C

Two new furanocoumarins, lucidafuranocoumarins B (1) and C (2), were isolated from the twigs of Feroniella lucida, together with five known compounds (3–7). The structures of these compounds were identified on the basis of extensive spectroscopic methods. The absolute configurations of lucidafuranocoumarin C at C-2″ and C-5″ were established as R- and S-configurations, respectively, by applying Mosher's method. Some isolates were also evaluated for their cytotoxicity against KB, MCF-7 and NCI-H187 cell lines.     

Minor xanthones from Rheedia gardneriana

8-Deoxygartanin and two new xanthones, 1,5-dihydroxy-6′,6′-dimethyl-2H-pyrano(2′,3′:3,2)-6″,6″-dimethyl-2H-pyrano(2″,3″:6,7)xanthone and 1,5,6-trihydroxy-6′,6′-dimethyl-2H-pyrano(2′,3′:3,2)-7-(3-methylprop-2-enyl)xanthone, have been isolated from the roots of Rheedia gardneriana. The latter of the two new xanthones has been assigned the trivial name 7-prenyljacareubin while the former has the structure erroneously assigned to pyranojacareubin reported from Garcinia densivenia. The correct identity of the G. densivenia xanthone has been shown to be rheediaxanthone-A.     

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.     

Effect of laboratory containment on the nitrogen metabolism of termites

When Nasutitermes exitiosus, Nasutitermes walkeri and Coptotermes lacteus were brought into the laboratory they rapidly lost, within 24–48 hr, their ability to fix dinitrogen. With N. exitiosus and N. walkeri the loss was linear over the first 26–32 hr at a rate of about 3–4% per hour. N. walkeri completely lost its ability to fix dinitrogen and did not recover it during a further 11 days in the laboratory, whereas N. exitiosus and C. lacteus partially recovered their dinitrogen fixing ability to about 25–50% of the original rate. During laboratory storage of up to 60 days both C. lacteus and N. exitiosus gradually lost total nitrogen, while at the same time their uric acid content increased. The uric acid content of N. walkeri increased during 17 days in the laboratory while total nitrogen remained essentially constant. Xanthine dehydrogenase was not detected in freshly-collected N. walkeri but was detectable after two days of laboratory storage and reached a maximum activity in 8–10 days. The rate of dinitrogen fixation, total nitrogen and uric acid of field populations of N. exitiosus and N. walkeri (tested within 2 hr of collection) remained within close limits over a 6–8 week period, indicating that the changes in these parameters observed in populations kept in the laboratory did not occur in field populations. In field populations of N. walkeri the total nitrogen was about 1.4% of the fresh weight (6.7% of the dry weight) and the uric acid content was about 1.3% of the fresh weight (6.6% of the dry weight), with the amount of total nitrogen present as uric acid being about 31%. In N. exitiosus these values were: total nitrogen about 1.6% of the fresh weight (7.4% of the dry weight), uric acid about 0.6% of the fresh weight (2.9% of the dry weight), with uric acid accounting for about 13% of total nitrogen. When workers of N. walkeri were stored in a container near their nest they lost dinitrogen fixing ability to the same extent as workers brought into the laboratory, indicating that disruption of the nest was sufficient to affect dinitrogen fixation.     

Novel azalides derived from 16-membered macrolides. III. Azalides modified at the C-15 and 4″ positions: Improved antibacterial activities

The design and synthesis of 16-membered azalides modified at the C-15 and 4″ positions are described. The compounds we report here are characterized by an arylpropenyl group attached to the C-15 position of macrolactone and a carbamoyl group at the C-4″ position in a neutral sugar. Introduction of alkylcarbamoyl groups to the C-4″ position was regioselectively achieved by unique and convenient methods via acyl migration. As a result of optimization at the C-3 and 15 positions, several compounds were found to have potent activity against mef- and erm-resistant bacterial strains. These results suggest that 16-membered azalides could be promising compounds as clinical candidates.     

Prenylated xanthones from mangosteen as promising cholinesterase inhibitors and their molecular docking studies

Garcinia mangostana is a well-known tropical plant found mostly in South East Asia. The present study investigated acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities of G. mangostana extract and its chemical constituents using Ellman's colorimetric method. Cholinesterase inhibitory-guided approach led to identification of six bioactive prenylated xanthones showing moderate to potent cholinesterases inhibition with IC₅₀ values of lower than 20.5 μM. The most potent inhibitor of AChE was garcinone C while γ-mangostin was the most potent inhibitor of BChE with IC₅₀ values of 1.24 and 1.78 μM, respectively. Among the xanthones, mangostanol, 3-isomangostin, garcinone C and α-mangostin are AChE selective inhibitors, 8-deoxygartanin is a BChE selective inhibitor while γ-mangostin is a dual inhibitor. Preliminary structure-activity relationship suggests the importance of the C-8 prenyl and C-7 hydroxy groups for good AChE and BChE inhibitory activities. The enzyme kinetic studies indicate that both α-mangostin and garcinone C are mixed-mode inhibitors, while γ-mangostin is a non-competitive inhibitor of AChE. In contrast, both γ-mangostin and garcinone C are uncompetitive inhibitors, while α-mangostin is a mixed-mode inhibitor of BChE. Molecular docking studies revealed that α-mangostin, γ-mangostin and garcinone C interacts differently with the five important regions of AChE and BChE. The nature of protein–ligand interactions is mainly hydrophobic and hydrogen bonding. These bioactive prenylated xanthones are worthy for further investigations.     

Acylated luteolin glucosides from Salix gilgiana

Besides apigenin and luteolin 7-glucoside, four novel luteolin glucosides acylated with acetic,trans-cinnamic,p-coumaric andferulic acids, re acyl groups was determined to be at C-6″ by the¹³C NMR spectral data.     

Three biflavonoids from Daphne odora

Three new biflavonoids, daphnodorins G-I, were isolated from the roots of Daphne odora and their structures established from spectral and chemical means. These are two C-7/C-2″, C-8/C-3″ biflavonoids (upper half: apigenin, lower half: afzelechin), daphnodorins G and H and a spirobiflavonoid, daphnodorin I.     

Étude par R.M.N.-13C et -1h du (1→6)-β-d-glucane et des oligosaccharides linéaires et cycliques correspondants

The results of ¹H-n.m.r. and ¹³C-n.m.r. studies of linear and cyclic oligosaccharides in the series of gentiodextrins, both in their hydroxylated and acetylated form, were compared to those obtained for the corresponding natural or synthetic polysaccharide. The ¹³C-signals of each d-glucopyranose unit of acetylated oligosaccharides are more distinct than those of the parent hydroxylated compounds. In order to relate the change of the various signals with the degree of polymerization, gentiotriose undecaacetate, enriched in ¹³C at C-1″, was prepared, as well as gentiotetraose tetradecaacetate selectively labeled at C-1″ and C-1?. A (1→6)-β-d-glucan having a D.P. of ～10 was chemically prepared. During the course of the polycondensation, the 2,3,4,2′,3′,4′-hexa-O-acetyl-di-β-d-glucopyranosyl 1,6′:6,1′-di-anhydride, and the 2,3,4,2′,3′,4′,2″,3″,4″,2?,3?,4?-dodeca-O-acetyl-tetra-β-d-glucopyranosyl 1,6?:6,1?-tetraanhydride, respectively, were formed.     

Polyoxygenated xanthones of Centaurium littorale

Two apolar tetra-oxygenated xanthones (1,8-dihydroxy-3,5-dimethoxyxanthone and 1-hydroxy-3,5,8-trimethoxyxanthone) and two hexaoxygenated xanthones (1,8-dihydroxy-3,5,6,7-tetramethoxyxanthone and 1-hydroxy-3,5,6,7,8-pentamethoxyxanthone) have been isolated from the root of Centaurium littorale. The isolation and structure of these xanthones are reported and details of the TLC analysis are given. The ¹³C NMR and high resolution EIMS spectra of the two hexaoxygenated xanthones are reported. The xanthones found within the genus Centaurium Hill are reviewed.     

Structure–activity relationships of diverse xanthones against multidrug resistant human tumor cells

Thirteen xanthones were isolated naturally from the stem of Securidaca inappendiculata Hassk, and structure-activity relationships (SARs) of these compounds were comparatively predicted for their cytotoxic activity against three human multidrug resistant (MDR) cell lines MCF-7/ADR, SMMC-7721/Taxol, and A549/Taxol cells. The results showed that the selected xanthones exhibited different potent cytotoxic activity against the growth of different human tumor cell lines, and most of the xanthones exhibited selective cytotoxicity against SMMC-7721/Taxol cells. Furthermore, some tested xanthones showed stronger cytotoxicity than Cisplatin, which has been used in clinical application extensively. The SARs analysis revealed that the cytotoxic activities of diverse xanthones were affected mostly by the number and position of methoxyl and hydroxyl groups. Xanthones with more free hydroxyl and methoxyl groups increased the cytotoxic activity significantly, especially for those with the presence of C-3 hydroxyl and C-4 methoxyl groups.     

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.     

The major flavonoids of the seed of Tephrosia apollinea

A total of six complex 7-oxygenated-8-prenylflavones have been isolated from the seeds of Tephrosia apollinea and identified as the diastereoisomers (?)-semiglabrin and (?)-pseudosemiglabrin, (+)-glabratephrin, (+)-glabratephrinol, appollinine (7-methoxy-8-[3″-(2″,5″-dihydro-5″,5″-dimethyl-2″-oxofuryl)]-flavone and lanceolatin-A. The use of ¹³C NMR in the structure elucidation of flavones of this type is discussed. The potential chemotaxonomic value of Tephrosia flavones of the type isolated from T. apollinea is explored.     

Two chemically distinct groups of calophyllum species from Sri Lanka

The leaf extracts of Calophyllum moonii and C. walkeri were investigated. The former contained neoflavonoids whereas the latter had calozeylanic acid. Distribution of natural products in the leaf extracts of seven Calophyllum species has been reviewed and the existence of two chemically distinct groups in Calophyllum species has been recognized.     

Studies on Radiation Chemistry of Halogenophenols in Aqueous Solutions

Among the γ-radiolysis products of p-bromophenol in an aqueous solution, four new oligomers were obtained. By chemical and physical techniques their structures were elucidated as ortho-, meta- and para-terphenyl in which C-4, C-2′ and C-4″ are substituted by hydroxyl groups and C-5′ by a bromine atom and as 5-bromo-2,4′,4″-trihydroxy-m-terphenyl, respectively. These oligomers may be formed by the arylation of p-bromophenol or the dimeric product with an aryl radical intermediate resulted from debromination of p-bromophenol by some radiolysis product(s) of water.     

Xanthones protects lead-induced chronic kidney disease (CKD) via activating Nrf-2 and modulating NF-kB,MAPK pathway

Xanthones from a tropical fruit of Garcinia mangostana L. is known to possess a wide spectrum of pharmacologic properties, including antioxidant, anti-bacterial, anti-inflammatory, and antidiabetic activities. The current study aimed to assess the possible protective effects of xanthones against lead acetate (PbAc)-induced chronic kidney disease (CKD). To accomplish, in vitro antioxidant assays of xanthones, in vivo oxidative stress parameters, histopathology, inflammatory parameters were evaluated using PbAc-induced IRC male mice. The study was supported by in silico molecular docking of respective organ receptor protein-ligand interaction. Results revealed that xanthones potentially scavenged the DPPH, superoxide, hydroxyl, and nitric oxide radicals. Oxidative stress, kidney dysfunction, inflammatory markers, and kidney apoptosis increased by PbAc were attenuated with the co-treatment of xanthones. The treatment remarkably improved the tissue architecture. Of note, in silico prediction of activity study showed that protective role of xanthones could be due to its efficacy to activate the Nrf-2, regulate the intracellular [Ca²⁺], as well as downregulate the NF-kB, MAPK pathway. In a nutshell, xanthones could be a potential candidate for the management of PbAc-induced kidney damage.     

Four isoflavanones from the stem bark of Platycelphium voënse

From the stem bark of Platycelphium voënse (Leguminosae) four new isoflavanones were isolated and characterized as (S)-5,7-dihydroxy-2′,4′-dimethoxy-3′-(3″-methylbut-2″-enyl)-isoflavanone (trivial name platyisoflavanone A), (±)-5,7,2′-trihydroxy-4′-methoxy-3′-(3″-methylbut-2″-enyl)-isoflavanone (platyisoflavanone B), 5,7-dihydroxy-4′-methoxy-2″-(2?-hydroxyisopropyl)-dihydrofurano-[4″,5″:3′,2′]-isoflavanone (platyisoflavanone C) and 5,7,2′,3″-tetrahydroxy-2″,2″-dimethyldihydropyrano-[5″,6″:3′,4′]-isoflavanone (platyisoflavanone D). In addition, the known isoflavanones, sophoraisoflavanone A and glyasperin F; the isoflavone, formononetin; two flavones, kumatakenin and isokaempferide; as well as two triterpenes, betulin and β-amyrin were identified. The structures were elucidated on the basis of spectroscopic evidence. Platyisoflavanone A showed antibacterial activity against Mycobacterium tuberculosis in the microplate alamar blue assay (MABA) with MIC = 23.7 μM, but also showed cytotoxicity (IC₅₀ = 21.1 μM) in the vero cell test.     

An alkaloid from Haplophyllum tuberculatum

A new alkaloid (+)-tuberine was isolated from Haplophyllum tuberculatum. Physicochemical and spectral evidence established its structure and stereochemistry as N- benzoyl-4′-[(2″S,3″S,6″S)-(+)-7″-acetoxy-2″-hydroxy-3″,7″-dimethyl-3″,6″-epoxyoctyloxy]phenethylamine.     

Chemical constituents from Gentianella turkestanorum (Gentianaceae)

Phytochemical investigation of Gentianella turkestanorum (Gentianaceae) afforded nineteen compounds, including six xanthones (1–6), two triterpenoids (7–8), eight flavones (9–16) and three iridoids (17–19). Here, we firstly reported that 1-hydroxy-3,5-dimethoxyxanthone (4), 1, 8-dihydroxy-3-methoxyxanthone (5), apigenin (9), quercetin (10), luteolin-7-O-glucoside (12) and three other compounds (1, 8-dihydroxy-3-methoxyxanthone (5), apigenin-7-O-gluco (1″ → 3‴) glucoside (15) and luteolin-7-O-gluco (1″ → 3‴) glucoside (16)) could be isolated from G. turkestanorum. The occurrence of chemical data and the sequence data might be employed as common constituents of the genera Gentianella, Lomatogonium and Swertia.     

Apigenin 7-glucoside and its 2″- and 6″-acetates from ligulate flowers of Matricaria chamomilla

Dried ligulate flowers of Matricaria chamomilla contain 7–9% glucosides of apigenin and 0.3–0.5% free apigenin. Glucosides were identified as apigenin 7-glucoside and a 1:3 mixture of the 2″- and 6″-acetates, as determined by ¹³C NMR analysis.