Mehreen Lateef

Mild and efficient synthesis of new tetraketones as lipoxygenase inhibitors and antioxidants

A mild and efficient route to tetraketones (2–22) has been developed by way of tetraethyl ammonium bromide (Et4N+Br− ) mediated condensation of dimedone (5,5-dimethylcyclohexane-1,3-dione, 1) with a variety of aldehydes. All these compounds showed significant lipoxygenase inhibitory activity and moderate to strong antioxidant potential. Compounds 19 (IC50 = 7.8 μM), 22 (IC50 = 12.5 μM), 3 (IC50 = 16.3 μM), 11 (IC50 = 17.5 μM) and 8 (IC50 = 21.3 μM) showed significant inhibitory potential against lipoxygenase (baicalein, IC50 = 22.4 μM). On the other hand compound 19 (IC50 = 33.6 μM) also showed strong antioxidant activity compared to the standard (IC50 = 44.7 μM). This study is likely to lead to the discovery of therapeutically efficient agents against very important disorders including inflammation, asthma, cancer and autoimmune diseases.

Antioxidant constituents from Cotoneaster racemiflora

A new lignan rhamnoside, racemiside (1), has been isolated from the ethyl acetate-soluble fraction of Cotoneaster racemiflora, along with scopoletin (2), 7,8-dimethoxy-6-hydroxycoumarin (3), 3,3′,4′-tri-O-methylellagic acid (4), and cereotagloperoxide (5), reported for the first time from this species. All of them showed profound antioxidative activities in the DPPH assay.

Ophiamides A-B, new potent urease inhibitory sphingolipids from Heliotropium ophioglossum

Ophiamides A (1) and B (2), two new sphingolipids have been isolated from the n-hexane subfraction of the MeOH extract of the whole plant of Heliotropium ophioglossum along with glycerol monopalmitate (3) and β-sitosterol 3-O-β-d-glucoside (4) reported for the first time from this species. Their structures were elucidated by spectroscopic techniques including MS and 2D-NMR spectroscopy. Both the compounds 1 and 2 showed potent inhibitory activity against the enzyme urease.

Urease inhibitory isoflavonoids from different parts of Calopogonium mucunoides (Fabaceae)

The dichloromethane-methanol (1:1) soluble part of Calopogonium mucunoides (Fabaceae) resulted in the isolation of 10 isoflavones (4′-O-methylalpinumisoflavone, 4′-O-methylderrone, alpinumisoflavone, daidzeine, Calopogonium isoflavone A, atalantoflavone, 2′,4′,5′,7-tetramethoxyisoflavone, 7-O-methylcuneantin, cabreuvin and 7-O-methylpseudobaptigenin) and a rotenoid (6a,12a-dehydroxydegueline). Among these, daidzeine, 7-O-methylcuneantin, atalantoflavone and 6a, 12a-dehydroxydegueline have been isolated for the first time from C. mucunoides while remaining are already reported from this source. Structures of all the isolated constituents were elucidated with the aid of NMR spectroscopic and mass spectrometric techniques. Among all the isolated constituents, nine were evaluated for their urease inhibitory potential. However, six were found potent. These include 4′-O-methylderrone, daidzeine, atalantoflavone, 2′,4′,5′,7-tetramethoxyisoflavone, 7-O-methylcuneantin and 6a, 12a-dehydroxydegueline.

A new glycosidic antioxidant from Ranunculus muricatus L. (Ranunculaceae) exhibited lipoxygenasae and xanthine oxidase inhibition properties.

Abstract Phytochemical investigation of Ranunculus muricatus L. (Ranunculaceae) led to the isolation of a new metabolite named as ranuncoside from the ethyl acetate fraction of the plant. Structure of the novel compound was elucidated through detailed spectroscopic analyses, using UV, IR, 1H, 13C NMR and 2D NMR in combination with EIMS and HR EI-MS techniques. The compound was evaluated for antioxidant activity using the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging assay. Its inhibitory potential was tested against lipoxygenase and xanthine oxidase enzymes. Ranuncoside potently scavenged the DPPH free radicals (IC50 = 56.7 ± 0.43 μM) and strongly inhibited the activities of lipoxygenase (IC50 = 63.9 ± 0.17 μM) and xanthine oxidase (IC50 = 43.3 ± 0.22 μM).

Biologically Active Bergenin Derivatives from Bergenia stracheyi

New bergenin derivatives, bergecins A and B (1 and 2, resp.), have been isolated from the AcOEt‐soluble fraction of Bergenia stracheyi, along with bergenin (3), and their structures were elucidated on the basis of 1H‐ and 13C‐NMR spectra, and by COSY, HMQC, and HMBC experiments. Compound 2 showed potent inhibitory potential against the enzyme lipoxygenase, while 1 was moderately active. On the other hand, both compounds exhibited significant antioxidant activities in 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) scavenging assay.

Mutiniside, new antioxidant phenolic glucoside from Abutilon muticum

Mutiniside (1), new phenolic glucoside, and the flavonoidal glucoside cephacoside (2) have been isolated from the n-BuOH soluble fraction, along with lupeol (3), β-sitosterol (4), stigmasterol (5), methyl-4-hydroxybenzoate (6), taraxacin (7), ursolic acid (8), and β-sitosterol-3-O-β-d-glucopyranoside (9), have been isolated from the EtOAc soluble fraction of Abutilon muticum. Compounds 2–9 are reported for the first time from this species. Compound 1 showed significant antioxidant activity while moderate inhibitory activity was observed against the enzyme lipoxygenase.

Cotonoates A and B, New Aromatic Esters from Cotoneaster racemiflora

Abstract Phytochemical investigation of the chloroform soluble fraction of the methanolic extract of Cotoneaster racemiflora resulted in the isolation of two new aromatic esters named cotonoates A (1) and B (2) along with the known compound methyl 3,4-dihydroxy-5-methoxybenzoate (3). The structures of the new compounds have been assigned on the basis of spectral analysis including 1D and 2D NMR techniques. Compound 3 shows significant antioxidant and lipoxygenase inhibitory activities.

Potent Antioxidant and Lipoxygenase Inhibitory Flavanone and Chalcone from Erythrina mildbraedii Harms (Fabaceae) of Cameroon

In continuation of our search for new secondary metabolites from African Erythrina species, E. mildbraedii of Cameroon was investigated. As a result of this study, a new flavanone (mildbone, 1) and a new chalcone (mildbenone, 2) have been obtained and characterized by spectroscopic means. Both the compounds exhibited significant antioxidant and moderate lipoxygenase inhibitory activities. Compounds 1 and 2 showed potent antioxidant activity even stronger than the positive control. Among both the compounds, mildbone (1) was found to be potent in both the assays. Graphical Abstract Potent Antioxidant and Lipoxygenase Inhibitory Flavanone and Chalcone from Erythrina mildbraedii Harms (Fabaceae) of Cameroon

Kostchyienones A and B, new antiplasmodial and cytotoxicity of limonoids from the roots of Pseudocedrela kotschyi (Schweinf.) Harms

Abstract Two new limonoids, kostchyienones A (1) and B (2), along with 12 known compounds 3–14 were isolated from the roots of Pseudocedrela kostchyi. Compound (7) was isolated for the first time from a natural source. Their structures were elucidated on the basis of spectroscopic evidence. Compounds 1–6 and 13–14 gave IC50 values ranging from 0.75 to 5.62 μg/mL for antiplasmodial activity against chloroquine-sensitive (Pf3D7) and chloroquine-resistant (PfINDO) strains of Plasmodium falciparum. Compound 5 showed moderate potential cytotoxicity against the HEK239T cell line with an IC50 value of 22.2±0.89 μg/mL. The antiplasmodial efficacy of the isolated compounds supports the medicinal value of this plant and its potential to provide novel antimalarial drugs.