DRYING EFFECT ON THE ISOLATION, CHARACTERIZATION AND ANTIOXIDANT POTENTIALS OF LEAF ESSENTIAL OILS OF Ocimum gratissimum HARVESTED AT 10:00am IN A DAY

Essential oils are volatile compounds found in special brittle secretory structures in plants, such as glands, they have several modes of actions as antioxidant, such as prevention of chain initiation and free radical scavenging. Ocimum gratissimum is an herbaceous plant which belongs to the Labiatae familyused in the treatment of epilepsy, high fever, diarrhea, mental illness, management of the baby’s cord, to keep the wound surfaces sterile and in the treatment of fungal infections, cold and catarrh. In this study, the antioxidant activity of Ocimum gratissimum in both fresh and dry leave is accessed. Pulverized fresh leaves (500g) of Ocimum gratissimum harvested at 10:00am in a day were air dried for five consecutive days and separately hydro-distilled for 3 hours. The oil yields range from 0.42-0.91% (w/w). Analysis of the oils using GC and GC-MS revealed the predominance of hydrocarbon sesquiterpenes (16.1-44.5%) and hydrocarbon monoterpenes (39.3-43.7)). The oils were predominated by α-thujene (14.6-24.5%), β-pinene(2.3-3%), α-terpinolene (9.3%), 1,3,8-p-menthatriene (1.8-3.5%), β-selinene (19.0-32.9%), Selina-3,7(11)-diene (5.6-12%), Isocarophillene (1.2-1.7%), β-Caryophyllene (8.5%), Humulene (2.3%), γ-cadinene (1.4%), E,Z-alloocimene (2.6-13.2%) and p-cymene (6.3-9.5%). α-phellandrene was detected in significant quantity (0.8%). The predominance of α-thujene and β-selinene in the oils shows that the oils were of α-thujene and β-selinene chemotypes. The free radical scavenging activities of oils were tested against2,2-diphenyl-1-picrylhydrazyl(DPPH). The oils were active against DPPH regardless of the level of dryness. The most and least active oils were the oils of leaves dried for four days (95.68±1.40) and two days (41.91±2.42) at 20µl/ml and IC50 of 4.29µl/ml and 20.05µl/ml respectively.