Study of lipids, glucosinolate-derived isothiocyanates and trheir antimicrobial activity of erucaria pinnata

Abstract EN

Background / aim : Brassicaceae is a large plant family; it includes vegetable crops, weeds, garden and wild flowers.

Erucaria pinnata is one of the most common species of this family, which mainly growing in Sirt region and locally known as Saleekh.

This study aim to isolate, identify lipid constituents and isothiocyanates and also to evaluate the potency of different extracts of Erucaria pinnata as antimicrobial agents.

Materials and Methods : the plant was collected from Sirt region in February 2008 during the flowering stage.

The aerial parts of the plant (leaves, flowers and branches) were air dried and ground until they become as a fine powder.

Instruments : Mass spectrophotometer GC / MS Jeol 500 Mass spectroscopy 70 eV.

Agilent Technologies 6890 N Network GC System.

Gas liquid chromatography Hewlett Packard HP 6890 series.

Isolation of Lipids : One kg of air dried powdered plant of Erucaria pinnata was extracted with n-hexane in a Soxhlet for 24 hours till exhaustion.

Extraction of the total Glucosinolates and Preparation of total isothiocyanates.

Antimicrobial activity : The antimicrobial activity was determined using the sensitivity disk diffusion method of Kirby-Bauer and determination of inhibitory zone (I.Z.).

Used microorganisms : Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Mycobacterium phlei, Enterobacter cloacae, Aspergillus niger and Candida albicans.

Results : The GLC analysis of E.

pinnata fatty acid methyl esters revealed the presence of six acids in which palmitic acid is the main one (65.10 %).

While the GLC analysis of the unsaponifiable matters revealed the presence of a series of long chain hydrocarbons with n-C20 and n-C29 are the main ones (13.45 % and12.88 % respectively).

Using GC / MS analysis for the obtained ITC after enzymatic hydrolysis of the total Glucosinolates, were identified as 8-methylsulfinyl octyl ITC, 4-methylsulfinyl-3-butenyl ITC, 2-phenylethyl ITC and 3-methylthio-2-propenyl ITC.

The results proved that, only total ITCs, Glucosinolates and butanol extract exhibited different inhibition effects against all tested organisms.

Ethyl acetate extract exhibited different inhibition effects against only tested Gram +ve bacteria, while, the acetone insoluble fraction and unsaponifiable matters showed no inhibition effects by any means against all tested microorganisms at all concentrations used.

Conclusion : the lipid constituents (fatty acids and unsaponifiable matters) of Erucaria pinnata were identified, also four isothiocyanates were isolated and identified using GC / MS.

The isolated isothiocyanates is more potent as antimicrobial than precursor Glucosinolates.