PROCEEDINGS OF 42 ND GSN ANNUAL CONFERENCE 2018 NIGERIAN DEFENCE ACADEMY 813 EVALUATION OF PHYTOCHEMICAL CONSTITUENTS, In vitro ANTIOXIDANT ACTIVITY AND ANTIMICROBIAL ACTIVITY OF THE LEAF EXTRACTS OF Ocimum basilicum (L) Adamu Aisha Isa 1 *, ThankGod Ositadinma Ndibe 2 and Benthai Benjamin 3 1 Department of Biochemistry, Ahmadu Bello University, Zaria. 2,3 Department of Biological Sciences, Nigerian Defence Academy, Kaduna. *Email address: aishadamuisa1141@gmail.com Phone Number: +2348060468355, +2348034282642, +2348061166247 ABSTRACT Since time immemorial, humans depend on plant resources for their benefit, from the recollection, as food and medicine. Medicinal plants contribute to the raw materials used for both traditional and modern systems of medicine. Among plants known for its medicinal importance, is Ocimum basilicum. This plant is widely used in Northern Nigeria, with little knowledge to its phytochemicals and antimicrobial properties. Need arises for an evaluation of the phytochemicals, antioxidant properties and antimicrobial activity of this indigenous Ocimum basilicum, with a view to access their therapeutic values. Standard methods were employed for the analyses. The result of phytochemical screening confirmed the presence of flavonoids, cardiac glycosides, tannins, saponins and phenols in both aqueous and methanolic extracts of the leaf. The quantitative estimation of chemical constituents of the leaf of the plant showed high percentage of flavonoids of 94.00% and 51.29% for aqueous and methanolic extracts respectively. The in vitro antioxidant activity of the plant extracts is due by its high concentration of flavonoids. The leaf extracts showed significant effect on Staphylococcus aureus, Bacillus subtilis and Shigella dysentriae. Salmonella typhi showed complete resistance to the leaf extracts. Methanolic extract of the leaf showed wide zone of inhibition of about 30mm against Staphylococcus aureus, with MIC and MBC of 1.56mg/ml and 3.125mg/ml respectively. The phytochemicals such as flavonoids and alkaloids obtained from the plant are appreciable. These are responsible for the ethno-medical, pharmacological, therapeutic and traditional uses of the plant. Keywords: Ocimum bacilicum, phytochemicals, antimicrobial and antioxidant. INTRODUCTION Healing with medicinal plants is as old as mankind itself. The connection between man and his search for drugs in nature, dates from far past (Ahmet et al., 2005). Awareness of medicinal plant usage is a result of many years of struggle against illnesses, in which case, many people learnt to pursue drugs from the barks, seeds, fruits bodies and other parts of plants. The knowledge of development of ideas related to the usage of medicinal plants as well as the evolution of awareness has increased the ability of pharmacists and physicians to respond to the challenges that have emerged with the spreading of professional services in facilitation of man’s life (Liu and Scagel, 2009). The medicinal plants are rich in secondary metabolites and essential oils of therapeutic importance (Meera et al., 2009). In Nigeria, many indigenous plants are widely consumed as food or home remedies especially in the treatment or management of common diseases. Among plants known for its medicinal value, is the plants Ocimum basilicum Linn of genus Ocimum, which is rich in phenolic compounds and are very useful for their therapeutic potential (Muralidharan and Dhananjayan, 2004). Methanolic extract of ocimum basilicum has been evaluated for its analgesic activity (Choudhury et al., 2010), antimicrobial activity against Pseudomonas aerogenosa (Harsh et al., 2002). Aqueous Ocimum basilicum has also been evaluated to have lipid lowering effect in Trinitron WR-1339-induced hyperlipidaemic rats (Ramesh and