International Journal of ChemTech Research CODEN (USA): IJCRGG ISSN : 0974-4290 Vol.6, No.14, pp 5554-5561, Nov-Dec 2014 Chemical Characterization and Investigation of the Bio- effects of the Leaves of Acanthus montanus (Acanthaceae) on Some Selected Microorganisms Okenwa U. Igwe* and Jude C. Nnaji Department of Chemistry, Michael Okpara University of Agriculture, Umudike, P.M.B. 7267 Umuahia, Abia State, Nigeria. *Corres.author: okescoty@yahoo.com; okenwauigwe@gmail.com, +234-806-386-2710; +234-705-150-9517. Abstract : The leaves of Acanthus montanus are used in traditional herbal practices in South Eastern Nigeria and in some other parts of West Africa for the treatment of gonorrhoea, syphilis, wounds and boils. Other uses of A. montanus in herbal medicine include the treatment of hypertension, cardiac dysfunctions, hepatitis and heart diseases. The chemical constituents of the ethanolic extract of the leaves of A. montanus were characterized using Gas Chromatography-Mass Spectrometry (GC/MS) technique and nine compounds were identified which include 2,6-bis(1,1-dimethylethyl)-4-methyl phenol (13.68 %), allyl(2-tetrahydrofuryl methoxy)dimethylsilane (3.86 %), sulfurous acid cyclohexylmethyl hexyl ester (5.67 %), alpha-methyl 4- methylmannoside (8.41 %), hexadecanoic acid methyl ester (16.12 %), 11-octadecenoic acid methyl ester (19.03 %), docosane (5.85 %), N,N-dimethylvaleramide (18.62 %) and 2,6,10,15-tetramethyl heptadecane (8.76 %). The extract exhibited marked antibacterial activity against Staphylococcus aureus, Enterococcus faecalis, Bacillus cereus, Escherichia coli, Salmonella typhi and Proteus mirabilis. The sensitivity of each test microorganism to the extract was determined using the Disc Diffusion Technique. The presence of these bioactive compounds in the leaves of A. montanus could be the reason behind its bacterial extermination effects as well as its concomitant use in the treatment of diseases and infections in herbal medicine in Nigeria. Keywords: Acanthus montanus, Chemical characterization, GC/MS analysis, Antibacterial activity 1. Introduction The flora and fauna that exist and evolve within the rainforest vegetation of South Eastern Nigeria no doubt provide a lot of benefits to the people. Prominent among these benefits is the provision of plant materials used in herbal medicine. These herbal plants possess bioactive compounds that impart desirable therapeutic properties in humans. Most of the compounds in these plants are yet to be fully explored. It is against this backdrop that the chemical composition and antimicrobial effects of the leaves of A. montanus are being investigated with a view to substantiate claims of its use as antibiotics in herbal medicine in South-east Nigeria. A. montanus (Nees) T. Anders belongs to the family Acanthaceae and is native to West Africa. The plant grows luxuriantly in Nigeria. It is an erect, prickly perennial plant that can grow up to 2 m tall. It has clusters of oblong to lance-shaped glossy, dark green leaves reaching up to 30 cm 1,2 . Leaves are opposite, glossy and papery in texture, deeply pinnately-lobed and the lobes have spines. The stem is stout woody and sparsely branching. The plant prefers shady situations and occasional deep watering, but tolerates sunny, dry situations too. It can perfectly survive steep areas because of its aggressive roots. The plant has been introduced to the rest of the world as an ornamental plant 1, 2 . A decoction of the leaves of A. montanus is used in the treatment of hypertension, cardiac dysfunctions