Antibacterial Activity And Phytochemical Screening Of Crude Ethanolic Extract Of Leaves Of Ocimum Gratissimum L On Listeria Monocytogenes.

摘要

Ethanolic extract of the leaves of Ocimum gratissimum was screened for its phytochemical and antibacterial properties on Listeria monocytogenes at varying concentrations. The Agar gel diffusion method was used to assay for the antibacterial properties on the test isolate. The results showed that the ethanolic extracts at different concentrations inhibited the growth of Listeria monocytogenes. The concentration of 250mg/ml inhibited the isolate with highest diameter zone of inhibition of 25mm. The extracts inhibited the growth of the bacterial isolate in a concentration dependent manner with MICs of 9.25mg/ml, while MBCs had 2.15mg/ml. Phytochemical analysis of the leaf extracts revealed the presence of antimicrobial active agents such as alkaloids, cardiac glycosides, flavonoids, glycosides, resins, steroidal terpens, and tannins. These established a good support to the use of this plant in herbal medcine and as base for the development of new drugs and phytomedicine. Introduction Medicinal plants have contributed immensely to health care in Nigeria. This is due in part to the recognition of the value of traditional medical systems, particularly in Asian origin, and the identification of medicinal plant from indigenous pharmacopoeias, which have significant healing power.Among all families of the plant kingdom, members of the Lamiaceae have been used for centuries in folk medicine. Ocimum gratissimum L (Lamiaceae), commonly known as “alfavaca” is naturally used in the treatment of different diseases, for example upper respiratory tract infections, diarrhoea, headache, fever, ophthalmic, skin disease and pneumonia (Correa 1932; Onajobi 1986; Ilori et al., 1996). The Ocimum oil is also active against several species of bacteria (Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Shigella, Salmonella and Proteus) and fungi (Trichophyton rubrum, T. mentagrophytes. Cryptococcus neoformans, Penicillum islandi cum, and Candida albicans (El-said et al., 1969; Begum et al., 1993; Nwosu and Okafor 1995; Akinyemi et al., 2004; Janine de Aquino Lemos et al., 2005; Lopez et al., 2005). Various species of Ocimum gratissimum for example O. viride Linn, O. suave Linn, O. basilicum Linn and O. canum Sims have been reported for their numerous medical uses (Mshana et al., 2000).Recent studies on Ocimum gratissimum proved to be a useful medication for people living with Human Immuno deficiency Virus (HIV), and Acquired Immuno Deficiency Syndrome virus AIDs (Elujoba, 2000). Spice or sweet basil is also thought to be an antispasmodic, carminative stimulant and insect repellant.It is said to have numerous properties, such as the tannins and sweet smelling volatile oil known to have antibacterial agent (Elujoba, 2000). The volatile oil also stops spasm, the hyperactivity of the gastrointestinal tract, by combining with the antibacterial activity and thus lowers the amount of times the muscle of the stomach and gastrointestinal tracts contracts stopping the diarrhoea (Elujoba, 2000) that are usually adverse for most other pathogenic bacteria. It can be isolated from soil, silage and other environmental sources (Patrick et al., 1995).The onset of Listeriosis is usually preceded by influenza-like symptoms (Martin and Fisher, 2000). The onset time to serious forms of Listeriosisis is known but may range from a few days to 3 weeks. The manifestation of Listeriosis is septicemia, meningitis (or meningoencephalitis), encephalitis, and intrauterine or cervical infections in pregnant women, which may result in spontaneous abortion or stillbirth. At present the infective dose of L. monocytogenes is unknown, although it is believed to vary with the strain and susceptibility of the victim (Marsden, 1994; Dimitrijeric and Teodorov, 1998; Curtis, 2000). Sometimes in susceptible persons, fewer than 103 cfu/g or ml may cause disease (Martin and Fisher, 2000).Over the past few years there have been published many studies that associate the consumption o