HIV-1 Tat interactions with cellular 7SK and viral TAR RNAs identifies dual structural mimicry.

The HIV Tat protein competes with the 7SK:HEXIM interaction to hijack pTEFb from 7SK snRNP and recruit it to the TAR motif on stalled viral transcripts. Here we solve structures of 7SK stemloop-1 and TAR in complex with Tat's RNA binding domain (RBD) to gain insights into this process. We find that 7SK is peppered with arginine sandwich motifs (ASM)-three classical and one with a pseudo configuration.

Analgesic principle from Curcuma amada.

Ethnopharmacological Relevance: The rhizome of Curcuma amada has been used as a folk medicine for the treatment of rheumatic disorders in the northern part of Bangladesh and has also used for the treatment of inflammation and fever in the Ayurvedic and Unani systems of medicine. Aim of the study was to investigate the analgesic principle of the MeOH extract of the rhizome of Curcuma amada by an in vivo bioassay guided chromatographic separation and purification, and the structure elucidation of the purified compound by spectroscopic methods.

Materials And Methods: Dried powder of Curcuma amada rhizomes was extracted with MeOH.

Fungal transformation of cedryl acetate and α-glucosidase inhibition assay, quantum mechanical calculations and molecular docking studies of its metabolites.

The fungal transformation of cedryl acetate (1) was investigated for the first time by using Cunninghamella elegans. The metabolites obtained include, 10β-hydroxycedryl acetate (3), 2α, 10β-dihydroxycedryl acetate (4), 2α-hydroxy-10-oxocedryl acetate (5), 3α,10β-dihydroxycedryl acetate (6), 3α,10α-dihydroxycedryl acetate (7), 10β,14α-dihydroxy cedryl acetate (8), 3β,10β-cedr-8(15)-ene-3,10-diol (9), and 3α,8β,10β -dihydroxycedrol (10). Compounds 1, 2, and 4 showed α-glucosidase inhibitory activity, whereby 1 was more potent than the standard inhibitor, acarbose, against yeast α-glucosidase.

Studies on α-glucosidase inhibition and anti-glycation potential of Iris loczyi and Iris unguicularis.

Aims: One of the aims of this research work is the isolation and identification of various constituents of two medicinally important plants (Iris loczyi and Iris unguicularis). Secondly, the prime aim is the biological evaluation of these natural products to discover new potential inhibitors of α-glucosidase enzyme and protein glycation.

Main Methods: Plants of the genus Iris contain a variety of secondary metabolites.

Duboscic acid: a potent α-glucosidase inhibitor with an unprecedented triterpenoidal carbon skeleton from Duboscia macrocarpa.

Duboscic acid (1), a triterpenoid with a unique carbon backbone, was isolated from Duboscia macrocarpa Bocq. It is the first member of a new class of triterpenoids, for which the name "dubosane" is proposed. Duboscic acid has a potent α-glucosidase inhibition, and its structure was unambiguously deduced by a single-crystal X-ray diffraction study.

Alpha-glucosidase and tyrosinase inhibitors from fungal hydroxylation of tibolone and hydroxytibolones.

Sixteen new and one known metabolites 4-20 were obtained by incubation of tibolone (1) and hydroxytibolones (2 and 3) with various fungi. Their structures were elucidated by means of a homo and heteronuclear 2D NMR and by HREI-MS techniques. The relative stereochemistry was deduced by 2D NOESY experiment.

Alpha-glucosidase inhibitors ellagic acid derivatives with immunoinhibitory properties from Terminalia superba.

Fractionation of stem barks of Terminalia superba yielded two new ellagic acid derivatives, 3,4'-di-O-methylellagic acid 3'-O-beta-D-xylopyranoside (1) and 4'-O-galloy-3,3'-di-O-methylellagic acid 4-O-beta-D-xylopyranoside (2) together with known 3,3'-di-O-methylellagic acid, ellagic acid and 3,3'-di-O-methylellagic acid 4'-O-beta-D-xylopyranoside. Compounds (1) and (2) showed significant alpha-glucosidase inhibition activity and possessed significant immunoinhibitory activities with no cytotoxic effects.

Microbial transformation of oleanolic acid by Fusarium lini and alpha-glucosidase inhibitory activity of its transformed products.

The biotransformation of a pentacyclic triterpene, oleanolic acid (1), with Fusarium lini afforded two oxidative metabolites, 2alpha,3beta-dihydroxyolean-12-en-28-oic acid (2), and 2alpha,3beta,11beta-trihydroxyolean-12-en-28-oic acid (3). Metabolite 3 was found to be a new compound. The structures were characterized on the basis of spectroscopic studies.

Bioactive aristolactams from Piper umbellatum.

Four alkaloids named piperumbellactams A-D (1-4) were isolated from branches of Piper umbellatum together with known N-hydroxyaristolam II (5), N-p-coumaroyl tyramine (6), 4-nerolidylcatechol (7), N-trans-feruloyltyramine, E-3-(3,4-dihydroxyphenyl)-N-2-[4-hydroxyphenylethyl]-2-propenamide, beta-amyrin, friedelin, apigenin 8-C-neohesperidoside, acacetin 6-C-beta-d-glucopyranoside, beta-sitosterol, its 3-O-beta-d-glucopyranoside and its 3-O-beta-d-[6'-dodecanoyl]-glucopyranoside. Glycosidase inhibition, antioxidant and antifungal activities of these compounds were evaluated. Compounds 1-3 showed moderate alpha-glucosidase enzyme inhibition with IC50 values 98.

alpha-Glucosidase inhibitory activity of triterpenoids from Cichorium intybus.

Two new triterpenoids, 18alpha,19beta-20(30)-taraxasten-3beta,21alpha-diol (cichoridiol) (1) and 17-epi-methyl-6-hydroxyangolensate (intybusoloid) (2), were obtained from the methanolic extract of seeds of Cichorium intybus along with 11 known compounds, lupeol (3), friedelin (4), beta-sitosterol (5), stigmasterol (6), betulinic acid (7), betulin (8), betulinaldehyde (9), syringic acid (10), vanillic acid (11) 6,7-dihydroxycoumarin (12), and methyl-alpha-D-galactopyranoside (13). Compounds 1, 1a, and 11 showed a good alpha-glucosidase inhibitory activity.

Further cytotoxic sesquiterpene lactones from Elephantopus mollis KUNTH.

Three new sesquiterpene lactones, (4betaH)-5alpha-hydroxy-8alpha-(2-methylbut-2-enoyloxy)-2-oxo-1(10),11(13)-guaiadien-12,6alpha-olide (1), (4betaH)-8alpha-(2-methylbut-2-enoyloxy)-2-oxo-1(5),10(14),11(13)-guaiatrien-12,6alpha-olide (2) and 2,5-epoxy-2beta-hydroxy-4alpha-methoxy-8alpha-(2-methylbut-2-enoyloxy)-4(15),10(14),11(13)-germacratrien-12,6alpha-olide (3), have been isolated from roots and stems of Elephantopus mollis together with two known sesquiterpene lactones (4, 5). The identification of the isolates was accomplished by spectroscopic methods. Compounds (1-5) exhibited significant cytotoxic activities against mouse neuroblastoma B104 cells.

Alpha-glucosidase inhibitors from Millettia conraui.

A new geranylated isoflavone, 7-O-geranyl-6-methoxypseudobaptigenin (1) was isolated from the stem barks of Millettia conraui, along with known compounds 5-methoxydurmillone (2), conrauinone A (3), beta-amyrine (4), sitosterol (5), 3-O-beta-D-glucopyranosyl sitosterol (6) and n-docosanol (7). Compounds 1 and 4 showed a significant alpha-glucosidase inhibitory activity. The structures of the compounds were determined by analysis of their spectroscopic data.

alpha-Glucosidase inhibitory pentacyclic triterpenes from the stem bark of Fagara tessmannii (Rutaceae).

In addition to fatty acids, a mixture of sterols (beta-sitosterol, stigmasterol, campesterol and stigmastanol), lupeol, arctigenin methylether, sesamin, vanillic acid (1), 2,6-dimethoxy-1,4-benzoquinone (2), betulinic acid and two pentacyclic triterpene acetates were isolated from Fagara tessmannii Engl. They were identified as 3beta-acetoxy-16beta-hydroxybetulinic acid (3a) and 3beta,16beta-diacetoxybetulinic acid (3b), and their structures were established using 1 and 2D NMR spectra and by comparison with published data. Two derivatives of the compounds were prepared.

Alpha-glucosidase inhibitory anthranols, kenganthranols A-C, from the stem bark of Harungana madagascariensis.

One new prenylated 1,4-anthraquinone and three new prenylated anthranols, named kengaquinone (1) and kenganthranols A (2), B (3), and C (4), were isolated from a hexane extract of the stem bark of Harungana madagascariensis. Six known compounds including anthraquinones, anthrones, and xanthones were also isolated and identified. The structures of the new compounds were determined by analysis of spectroscopic data and comparison with data of previously known analogues.

Structure determination of bioactive galloyl derivatives by NMR spectroscopy.

The investigation of the chemical constituents of Symplocos racemosa Roxb led to the isolation of two new glycosides, symcomoside A (1) and symcomoside B (2), together with one known glycoside, tortoside C (3), which is reported for the first time from this plant. The structures of the new compounds were determined by 1D and 2D homonuclear and heteronuclear NMR spectroscopy, from chemical evidence and by comparison with published data for closely related compounds. Symcomoside B (2) showed potent inhibitory activity against alpha-glucosidase in a concentration-dependent fashion with an IC50 value of 0.

Alpha-glucosidase inhibitory constituents from Duranta repens.

Three C-alkylated flavonoids 7-O-alpha-D-glucopyranosyl-3,5-dihydroxy-3'-(4"-acetoxyl-3"-methylbutyl)-6,4'-dimethoxyflavone (1), 7-O-alpha-D-glucopyranosyl-3,4'-dihydroxy-3'-(4"-acetoxyl-3"-methylbutyl)-5,6-dimethoxyflavone (2), 3,7,4'-trihydroxy-3'-(8"-acetoxy-7"-methyloctyl)-5,6-dimethoxyflavone (3) and a trans-clerodane type diterpenoid (-)-6beta-hydroxy-5beta,8beta,9beta,10alpha-cleroda-3,13-dien-16,15-olid-18-oic acid (4) are reported from Duranta repens along with (+)-hardwickiic acid (5) and (+)-3,13-clerodadien-16,15-olid-18-oic acid (6), isolated for the first time from this species. Their structures were established on the basis of the spectral methods, especially two dimensional (2D) NMR spectroscopy.