Yashodharan Kumarasamy

Screening seeds of Scottish plants for antibacterial activity.

Based on ethnopharmacological and taxonomic information, seeds of 21 Scottish plant species from 14 different families were obtained from authentic seed suppliers. Their n-hexane, dichloromethane and methanol extracts were assessed for antibacterial activity against 11 pathogenic bacterial species. Methanol extracts of 11 plant species showed significant antibacterial activity. Malva moschata and Prunus padus were active against five bacterial species, Reseda lutea against four, Centaurium erythraea and Crithmum maritimum against three, Calluna vulgaris against two, and Armeria maritima, Centaurea scabiosa, Daucus carota, Rosa canina and Stellaria holostea against one bacterial species. C. erythraea and P. padus were also active against methicillin resistant Staphylococcus aureus.

Bioactivity of secoiridoid glycosides from Centaurium erythraea.

As part of our on-going search for bioactive compounds from Scottish plants, two secoiridoid glycosides, swertiamarin and sweroside, have been isolated from the aerial parts of Centaurium erythraea Rafn (Family: Gentianaceae) by reversed-phase preparative HPLC coupled with a photo-diode-array detector. The structures of these compounds were elucidated unambiguously by UV, FABMS and extensive 1D and 2D NMR spectroscopic analyses and also by comparing experimental data with literature data. Antibacterial, free radical scavenging activities and general toxicity of these glycosides have been assessed. Both compounds inhibited the growth of Bacillus cereus, Bacillus subtilis, Citrobacter freundii and Escherichia coli. While swertiamarin was also active against Proteus mirabilis and Serratia marcescens, sweroside inhibited the growth of Staphylococcus epidermidis. Swertiamarin and sweroside exhibited significant general toxicity in brine shrimp lethality bioassay and the LD50 values were 8.0 microg/ml and 34 microg/ml, respectively, whereas that of the positive control podophyllotoxin, a well known cytotoxic lignan, was 2.79 microg/ml. Chemotaxonomic implications of these compounds in the family Gentianaceae have also been discussed briefly.

Bioactivity of Moschamindole from Centaurea moschata

The antioxidant and antibacterial properties of moschamindole (1), an indole alkaloid isolated from the methanol extract of the seeds of Centaurea moschata, have been assessed. General toxicity of this compound has also been determined by the brine shrimp lethality bioassay.

Bioactivity of gentiopicroside from the aerial parts of Centaurium erythraea.

Gentiopicroside (1), a secoiridoid glycoside isolated from the methanol extract of the aerial parts of Centaurium erythraea, has been assessed for antibacterial and free radical scavenging activities. General toxicity of 1 has also been determined by brine shrimp lethality bioassay.

Indole alkaloids from the seeds of Centaurea cyanus (Asteraceae)

Preparative RP-HPLC analysis of a methanol extract of the seeds of Centaurea cyanus afforded four indole alkaloids: moschamine, cis-moschamine, centcyamine and cis-centcyamine, the latter two being new natural products. Structures of these compounds were elucidated by comprehensive spectroscopic analyses. General toxicity of the isolates was determined by Brine Shrimp Lethality bioassay.

Isolation, Structure Elucidation, and Biological Activity of Flavone 6-C-Glycosides from Alliaria petiolata

Preparative reversed-phase HPLC analysis of a methanol extract of the seeds of Alliaria petiolata afforded fourflavone 6-C-glycosides: isoorientin, swertiajaponin, swertisin and isoscoparin-2″-β-D-glucopyranoside. The molecular structures were elucidated by UV, ESIMS and comprehensive 1D (1H and 13 C) and 2D (gradient multiple quantum filtered 1H-1H COSY, 1H-13C HSQC and 1H-13C HMBC) NMR analyses. The antibacterial and free radical scavenging activity, and general toxicity of these compounds were assessed. While none of these glycosides showed any significant antibacterial activities at test concentrations, all these compounds showed prominent free radical scavenging activity (IC50 values: 1.25×10-2 to 7.69×10-3 mg/mL) in DPPH assay. In the brine shrimp lethality assay very low levels of general toxicity (LD50 >1.00 mg/mL) were displayed.

Biological activity of serotonin conjugates from the seeds of Centaurea nigra

Two serotonin conjugates, N-(trans-p-coumaroyl)-serotonin (1) and N-(trans-feruloyl)-serotonin (maoschamine, 2), isolated from the methanol extract of the seeds of Centaurea nigra, have been assessed for antibacterial and free radical scavenging activities. The general toxicity of 1 and 2 has also been determined by the brine shrimp lethality bioassay.

Coumarins from the aerial parts of Prangos uloptera (Apiaceae)

Phytochemical studies on the aerial parts of Prangos uloptera, an endemic Iranian species of the genus Prangos, yielded five coumarins, xanthotoxin (1), prangenin (2), scopoletin (3), deltoin (4) and prangolarin (5). The structures of these coumarins were elucidated by spectroscopic means, and the antioxidant potential of 1-5 was evaluated by the DPPH assay. The chemotaxonomic significance of 1-5 is also discussed.

Antibacterial and free radical scavenging activity of the seeds of Agrimonia eupatoria.

n-Hexane, dichloromethane and methanol extracts of the seeds of Agrimonia eupatoria have been assessed for antibacterial and free radical scavenging activity.

Eremostachiin: a new furanolabdane diterpene glycoside from Eremostachys glabra

The reversed-phase preparative HPLC analysis of the methanol extract of the rhizomes of Eremostachys glabra (Lamiaceae) led to the isolation of two furanolabdane diterpene glycosides, phlomisoside II, and β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl ester of phlomisoic acid (named eremostachiin), the latter being a novel natural product. The structure of the new compound has been elucidated unambiguously by HRMS and a series of 1D- and 2D-NMR spectroscopic techniques. The free radical scavenging activity of these compounds was assessed using the DPPH assay.