Life Science Journal 2017;14(9) http://www.lifesciencesite.com 104 Ocimum basilicum var. purpureum Floral Essential Oil: Phytochemicals, Phenolic Content, Antioxidant, Free Radical Scavenging, Antimicrobial Potentials Ololade Z.S. 1* , Fakankun O.A. 1 , Alao, F.O. 2 , Udi O.U. 1 1 Department of Chemical Sciences, Bells University of Technology, P.M.B. 1015, Ota, Nigeria 2 Department of Biological Sciences, Bells University of Technology, P.M.B. 1015, Ota, Nigeria zacchsnatpdt@gmail.com; suntolgroup@yahoo.com Abstract: This study examined the phytochemicals and medicinal properties of the floral essential oil of O. basilicum var. purpureum from Nigeria. The GC and GC-MS analyses revealed the presence of twenty-five organic compounds making up 99.7% of the total percentage composition of the essential oil. The most abundant components was phenolic compound called methyleugenol (15.5%), followed by 2-phenyl-1-hexanol (14.0%), 1- (4,5-dimethyl-2-nitrophenyl)-1H-tetraazole (14.0%), 2-methyl-3,5-dodecadiyne (14.0%), o-nitrocumene (14.0%) and patchoulane (6.7%). The total phenolic content was quantitatively determined as 459 µgmg -1 gallic acid equivalent (GAE) confirming the presence of high amount phenolic compounds in the floral essential oil. The DPPH IC 50 value was 1.0 µgml -1 , the essential oil was capable of scavenging free radicals in a range of 86-73% and the antioxidant power of the essential oil increased with concentration. The essential oil was found to be 90% more active than the synthetic antioxidant (ascorbic acid). The essential oil was also found to exert excellent antibacterial properties compared to standard antibiotics. The floral essential oil was significantly active against all tested species of Gram-positive and Gram-negative bacteria with high zones of inhibition between 15-30mm. The bacteria inhibition of the essential oil was found to be positively correlated with their terpenoid and phenolic contents. The results from this study indicate that the floral essential oil show potential as a good source of natural antioxidant and antimicrobial drugs and may impart health benefits by its pharmacological property. [Ololade Z.S., Fakankun O.A., Alao, F.O., Udi O.U. Ocimum basilicum var. purpureum Floral Essential Oil: Phytochemicals, Phenolic Content, Antioxidant, Free Radical Scavenging, Antimicrobial Potentials. Life Sci J 2017;14(9):104-110]. ISSN: 1097-8135 (Print) / ISSN: 2372-613X (Online). http://www.lifesciencesite.com . 10. doi:10.7537/marslsj140917.10 . Keywords: Ocimum basilicum var. purpureum, floral essential oil, phytochemical, phenolic, pharmacological 1. Introduction Phytochemicals are huge variety of organic substances which accumulated in plants. Plant secondary metabolites, especially essential oils, are recognized as one of the most promising groups of natural compounds for the development of cheap and safer drugs (Varma and Dubey, 2001). Essential oils are volatile, natural and complex compounds characterized by a strong odour and are produced from odoriferous medicinal plants as secondary metabolites. In addition to essential oils, odouriferous plants are also characterized by the presence of phenolic compounds that have been shown to possess multiple pharmacological activities, Essential oils, their fractions and isolated aroma chemicals are valuable ingredients of flavour food and toiletries, fine chemicals, and pharmaceutical industries, and are utilized as such or in diluted forms in therapy or by the aromatherapy sector (Daferera et al., 2000; Mimica-Dukic and Bozin, 2008). According to world health organization (WHO), greater than 80% of the total world’s population depends on natural products in order to satisfy their primary health care needs. Investigations of these secondary metabolites intensified when some commercial synthetic antioxidants were found to exhibit toxic, mutagenic and carcinogenic effects and other problems associated with their usage (Rajendran et al., 2014). Knowledge of the chemical composition of medicinal plants is desirable because such information will be of value for the synthesis of complex chemical substances (Yadav and Agarwala, 2011). The genus Ocimum comprises more than 150 species and is considered as one of the largest genera of the Lamiaceae family. Ocimum basilicum var. purpureum is an annual plant which grows well in Nigeria. The purple colour of the plant is due to the presence of anthocyanins mainly cyanidin-3-(di-p- coumarylglucoside)-5-glucoside) and small amount of peonidin compounds, therefore, this plant is considered a potential source of red pigments for the food industry (Janick et al., 1999). The plant is widely used in food and oral care products. The plant is a good source of magnesium, which promotes cardiovascular health, also helps muscles and blood vessels to relax, thus improving blood flow and lessening the risk of irregular heart rhythms or a spasming of the heart muscle or a blood vessel. It is also an excellent source of vitamin K and manganese; a very good source of copper, vitamin A and vitamin