Abstract
Ixora coccinea L. (Rubiaceae) has been used traditionally for a variety of ailments and also cultivated for ornamental purposes. The present study investigated antimicrobial activity of methanolic extracts of various parts of I. coccinea and determined the chemical groups of the active constituents. Antimicrobial activity was assessed using agar disc diffusion, microdilution and thin layer chromatography (TLC) bioautography assays. Methanolic extracts of leaf, flower and stem of I. coccinea displayed good antimicrobial activity, with inhibition zone in the range of 6.7 to 11.3 mm. minimum inhibitory concentration (MIC) values for all three extracts ranged from 0.78 to 3.125 mg/ml. Leaf and stem extracts of I. coccinea showed broad-spectrum antimicrobial activity. Of interest, stem extracts had MIC values against Staphylococcus aureus that were only 62.4 times less potent than the vancomycin. Likewise, leaf and stem extracts displayed good antimicrobial activity of 62.4 and 31.2 times, respectively lesser than gentamycin against Shigella flexneri. Minimum bactericidal/ bacteriostatic concentration (MBC) values for active extracts ranged from 0.78 to 6.25 mg/ml. TLC bioautography and phytochemical screening of the leaf and stem extracts showed that the antimicrobial activity of these extracts may be attributed to compounds belonging to terpenoid, flavonoid, coumarin, alkaloid and phenolic groups. Key words: Antimicrobial, Ixora coccinea, minimum inhibitory concentration, minimum bacteriostatic/bacteriocidal concentration, bioautography.
Highlights
Plants are the oldest source of pharmacologically active substances and have provided humans with many medically useful compounds (Cordell, 1981)
The present study investigated antimicrobial activity of methanolic extracts of various parts of I. coccinea and determined the chemical groups of the active constituents
Natural products in particular medicinal plants remain as a potential source of new antimicrobial agents (Cowan, 1999)
Summary
Plants are the oldest source of pharmacologically active substances and have provided humans with many medically useful compounds (Cordell, 1981). Annapurna et al (2003) has reported the antimicrobial activity of I. coccinea leaf extract based on disc diffusion method. There is no in depth antimicrobial evaluation done on this plant With this in view, the present study was undertaken to evaluate in detail the antimicrobial activity of methanolic extract of various parts of I. coccinea against series of microorganisms and to identify the chemical groups of the bioactive constituents. A 50 mg/ml stock solution of each extract (leaf, flower and stem) was prepared in methanol. Fresh plant materials of I. coccinea (leaves, flowers and stem) were collected from Penang, Malaysia. Amoxicillin, chloramphenicol, vancomycin and gentamycin (for bacteria) and miconazole (for fungus) served as positive controls, respectively while 50% DMSO was used as negative control.
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