Asif Ali

Terminoside A, a new triterpene glycoside from the bark of Terminalia arjuna inhibits nitric oxide production in murine macrophages

Terminoside A (1), a new oleanane-type triterpene was isolated from the acetone fraction of the ethanolic extract of stem bark of Terminalia arjuna. The structure was established as olean-1α,3β,22β-triol-12-en-28-oic acid-3β-D-glucopyranoside. On the basis of spectral data and chemical reactions, terminoside A, potently inhibited nitric oxide (NO) production and decreased inducible nitric oxide synthase (iNOS) levels in lipopolysaccharide-stimulated macrophages.

Bioactive metabolites from an endophytic Cryptosporiopsis sp. inhabiting Clidemia hirta

An endophytic Cryptosporiopsis sp. was isolated from Clidemia hirta and analyzed for its secondary metabolites that lead to the isolation of three bioactive molecules. The compounds were purified from the culture broth of the fungus and their structures were determined by spectroscopic methods as (R)-5-hydroxy-2-methylchroman-4-one (1), 1-(2,6-dihydroxyphenyl)pentan-1-one (2) and (Z)-1-(2-(2-butyryl-3-hydroxyphenoxy)-6-hydroxyphenyl)-3-hydroxybut-2-en-1-one (3). Compound 1 exhibited significant cytotoxic activity against the human leukemia cell line, HL-60 with an IC50 of 4 μg/ml. This compound induced G2 arrest of the HL-60 cell cycle significantly. In addition, out of these compounds, 2 and 3 were active against several bacterial pathogens. Compound 2 was active against Bacillus cereus, Escherichia coli and Staphylococcus aureus with IC50 values varying from 18 to 30 μg/ml, and compound 3 displayed activity against Pseudomonas fluorescens with an IC50 value of 6 μg/ml. Compounds 2 and 3 are novel whereas compound 1 was reported earlier but the stereochemistry of its C-2 methyl is established for the first time.

A new approach to construct full-length glycosylphosphatidylinositols of parasitic protozoa and [4-deoxy-Man-III]-GPI analogues

A new [2 + 2 + 2] approach to construct GPI molecules through the efficient synthesis of glucosamine-inositol and tetramannose intermediates led to a total synthesis of a GPI-anchor of Trypanosoma cruzi, and also afforded a key intermediate for the synthesis of valuable [4-deoxy-Man-III]-GPI analogues.

Phialomustin A–D, new antimicrobial and cytotoxic metabolites from an endophytic fungus, Phialophora mustea

Phialomustin A–D (1–4), four new bioactive metabolites, with an unprecedented azaphilone derived skeleton, were isolated and characterized from an endophytic fungus isolated from Crocus sativus. The ITS-5.8S-ITS2 ribosomal gene sequence of the endophyte displayed a sequence similarity of more than 99% with Phialophora mustea. The structural determinations of compounds (1–4) were authenticated by spectroscopic and chemical analysis. The absolute configuration of the stereogenic centers of 1, 3 and 4 were determined by electronic circular dichroism spectroscopy. Compounds 3 and 4 showed promising antifungal activities against Candida albicans, with IC50 values of 14.3 and 73.6 μM, whereas compound 2 exhibited remarkable cytotoxic activity against the human breast cancer cell line, T47D, with an IC50 of 1 μM.

Two new bioactive oleanane triterpene glycosides from Terminalia arjuna

Two new oleanane-type triterpene glycosides designated as Termiarjunoside I and Termiarjunoside II were isolated from stem bark of Terminalia arjuna (Combretaceae) and characterized as olean-1α,3β,9α,22α-tetraol-12-en-28-oic acid-3β-D-glucopyranoside (1) and olean-3α,5α,25-triol-12-en-23,28-dioic acid-3α-D-glucopyranoside (2) based on chemical and spectral data evidences. Both compounds 1 and 2 potently suppressed the release of nitric oxide and superoxide from macrophages and also inhibited aggregation of platelets.

HPTLC determination of artesunate as bulk drug and in pharmaceutical formulations

A new, simple, rapid, accurate and precise HPTLC method has been developed for the estimation of artesunate in bulk and pharmaceutical formulations. The study employs silica gel F 254 as stationary phase on aluminium foil and mobile phase comprising toluene: ethyl acetate: acetic acid (2:8:0.2). Vanillin (1%) in sulphuric acid (5%) in ethanolic solution gave prominent well-resolved pink colour spot for artesunate, which was stable for more than a day. The densitometric analysis was carried out in the absorbance mode at 520 nm and symmetrical, well-resolved, well-defined peaks were obtained. The Rf value for artesunate was found to be 0.44. The linear detector response for artesunate was observed between 100-600 ng per spot and the calibration plots showed good linear relationship with coefficient of regression, r= 0.9989 with respect to peak area. The method was validated for precision, recovery and robustness. The limits of detection and quantitation were 30 ng/spot and 90 ng/spot, respectively. The recovery study was carried out by standard addition method and the recovery was found to be 99.89±1.006. Recovery from tablets was 98.88 (±0.55) and from injection, it was 98.83 (±0.60) of the labeled amount.

Anti-inflammatory and Analgesic Activity of Uraria lagopoides

Anti-inflammatory activity of alcohol and aqueous extract of aerial parts of Uraria lagopoides was determined in the rat paw edema test. At doses of 100 and 200 mg/kg, oral, the extract inhibited edema significantly (p < 0.01) compared with indomethacin (20 mg/kg). It also showed marked analgesic activity in mice (p < 0.01), compared with acetylsalicylic acid (100 mg/kg) in acetic acid-induced writhing test.

Production of rohitukine in leaves and seeds of Dysoxylum binectariferum: An alternate renewable resource

Abstract Context: Rohitukine is an important precursor for the synthesis of potential anticancer drugs flavopiridol (Sanofi-Aventis) and P-276-00 (Piramal Healthcare Limited, Mumbai, India). Trunk bark of Dysoxylum binectariferum (Roxb.) Hook. f. ex Bedd. (Meliaceae) is the widely used source for isolation of rohitukine. However, removal of trunk bark threatens the survival of the tree. Objective: To investigate the amount of rohitukine accumulated in other tissues of D. binectariferum. Materials and methods: Rohitukine standard was isolated from leaves of D. binectariferum. Its purity was ascertained using HR-MS and NMR. Crude extracts were prepared from different tissues of D. binectariferum. Rohitukine content in all the tissues was quantified by HPLC. Results: Rohitukine accumulates in a significant amount in seeds, trunk bark, leaves, twigs, and fruits of D. binectariferum. Seeds have the highest rohitukine content (2.42%, dry weight) followed by trunk bark (1.34%, dry weight), leaves (1.064%, dry weight), twigs (0.844% dry weight), and fruits (0.4559% dry weight). Discussion and conclusion: Seeds and leaves of D. binectariferum could be used as alternate renewable sources for isolation of rohitukine.

An Insight into the Secondary Metabolism of Muscodor yucatanensis: Small-Molecule Epigenetic Modifiers Induce Expression of Secondary Metabolism-Related Genes and Production of New Metabolites in the Endophyte

Muscodor spp. are proficient producers of bioactive volatile organic compounds (VOCs) with many potential applications. However, all members of this genus produce varying amounts and types of VOCs which suggests the involvement of epigenetics as a possible explanation. The members of this genus are poorly explored for the production of soluble compounds (extrolites). In this study, the polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) genes from an endophyte, Muscodor yucatanensis Ni30, were cloned and sequenced. The PKS genes belonged to reduced, partially reduced, non-reduced, and highly reduced subtypes. Strains over-expressing PKS genes were developed through the use of small-molecule epigenetic modifiers (suberoylanilide hydroxamic acid (SAHA) and 5-azacytidine). The putative epigenetic variants of this organism differed considerably from the wild type in morphological features and cultural characteristics as well as metabolites that were produced. Each variant produced a different set of VOCs distinct from the wild type, and several VOCs including methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)hexane-2,4-diol and 2-carboxymethyl-3-n-hexylmaleic appeared in the variant strains, the production of which could be attributed to the activity of otherwise silent PKS genes. The bioactive extrolite brefeldin A was isolated and characterized from the wild type. However, this metabolite was not detected in EV-1, but instead, two other products were isolated and characterized as ergosterol and xylaguaianol C. Hence, M. yucatanensis has the genetic potential to produce several previously undetectable VOCs and organic solvent soluble products. It is also the case that small-molecule epigenetic modifiers can be used to produce stable variant strains of fungi with the potential to produce new molecules. Finally, this work hints to the prospect that the epigenetics of an endophytic microorganism can be influenced by any number of environmental and chemical factors associated with its host plant which may help to explain the enormous chemical diversity of secondary metabolic products found in Muscodor spp.

Chrysomycins A–C, antileukemic naphthocoumarins from Streptomyces sporoverrucosus

Two known naphthocoumarins, chrysomycins A (1) and B (2), along with one new naphthocoumarin chrysomycin C (3) were isolated from the antimicrobial strain of Streptomyces sporoverrucosus (MTCC11715) (isolated from soil samples from the Jammu hills) and characterized. The structure of the new compound 3 was established from 2D-NMR data. Chrysomycins A (1) and B (2) were identified using a strategic HPLC–PDA/LCMS and Dictionary of Natural Products (DNP) based fast dereplication. Additionally, two new naphthocoumarins, chrysomycins D and E were identified using LCMS, UV and DNP information. Chrysomycins A–C (1–3) were isolated for the first time from Streptomyces sporoverrucosus and were screened for cytotoxicity against a panel of cancer cell lines (A549, Colo205, PC-3, MIAPaCa-2, and HL-60), amongst which the most potent activity was observed against human leukemia HL-60 cells with IC50 values of 0.9, 0.95 and 11 μM, respectively. The mechanistic studies indicated that chrysomycins A (1) and B (2), at 1 μM concentration, distorted the cellular and nuclear morphology with significant DNA damage and apoptosis in HL-60 cells.