Phcog J | Sep–Oct 2012 | Vol 4 | Issue 31 47 ORIGINAL ARTICLE PHCOG J ABSTRACT Introduction: The genus Callistemon (family: Myrtaceae) contains 34 species which are widely distributed in the temperate regions and used in folk medicine. Methods: Chromatographic separation of 80% MeOH extract of the leaves of Callistemon viridiflorus (sims) Sweet (Cv) was performed. Results: Seven known polyphenolic compounds were isolated for the frst time from this species: gallic acid, ellagic acid, isoquercetin, hyperin, 1,2:3,4-(bis(s)- hexahydroxy diphenoyl-β-D-glucopyranose, nilocitin and quercetin-3-O-α-L-glucuronopyranoside. The methanolic extract of Cv leaves exhibited a signifcant anti-microbial activity against the tested microorganisms. Keywords: Myrtaceae, Callistemon viridiflorous, polyphenols, anti-microbial activity. Polyphenolic constituents of the methanolic extract of Callistemon viridiforous leaves and its antimicrobial activity Mohamed IS Abdelhady, 1* Amel M Kamal, 1 Nashwa F Tawfk 1 and Soad M Abdelkhalik 1 1 Pharmacognosy Department, Faculty of Pharmacy, Helwan University, Ain Helwan, Cairo, Egypt INTRODUCTION Family Myrtaceae (Myrtle family) comprises about 130–150 genera and about 5000 species of ever- green shrubs and trees. The genus Callistemon (family: Myrtaceae) contains 34 species which are widely dis- tributed in the temperate regions of Australia, and are widely distributed in warm-temperate regions. [1–5] The genus Callistemon (commonly named bottle brush plant) is known in folk medicine for its anticough, antibronchitis, antifungal, antibacterial, anti-infamma- tory, analgesic, anticonvulsant, antidiabetic, anti-hem- orrhoidal and antinociceptive activities. [6–13] Previous phytochemical investigations of some species of Cal- listemon genus resulted in the identifcation of C-methyl favonoids, falvonol glycosides, phenolic acids, hydro- lysable ellagitannins, triterpenoids and phloroglucinol derivatives. [4–19] Because of the biological importance of plant polyphenols, particularly tannins and favonoids, a phytochemical study was of interest to investigate the constitutive poyphenols in the extract of leaves for Callistemon viridiforous. Synonyms of the plant include Callistemon viridiforus (Sieber ex Sims) Sweet, Calliste- mon salignus var. viridiforus (Sieber ex Sims) F. Muell., Melaleuca virens Craven, Metrosideros viridifora Sieber ex Sims. [20] The present study deals with the isolation and identif- cation of some polyphenolic constituents of Callistemon viridiforous species growing in Egypt and to explore the antimicrobial activity of its methanolic extracts. MATERIALS Plant material Leaves of Callistemon viridiforus (Sims) Sweet were col- lected from Alexandria-Cairo Road, Egypt, in July, 2008. The plant was identifed by Dr. Trease Labeb, Lecturer of Taxonomy, Department of Floral and Taxonomy, Orman Garden, Cairo, Egypt. Microorganisms Gram-positive bacteria (Staphylococcus aureus ATCC4175), Gram-negative bacteria (E. coli) and yeast (candida albicans *Corresponding author. Mohamed I S Abdelhady Pharmacognosy Department, Faculty of Pharmacy, Helwan University, Ain Helwan, Cairo, Egypt E-mail: mohibrahem@yahoo.com DOI: 10.5530/pj.2012.31.9