Chemo-type of essential oil of Ocimum basilicum L. from DR Congo and relative in vitro antioxidant potential to the polarity of crude extracts

Abstract

ObjectiveTo carry out a phyto-chemical characterization of essential oil from Ocimum basilicum L. (O. basilicum) harvested in DR Congo and to assess the antioxidant potential of crude extracts with respect to the polarity for comparison reason. MethodsThe phyto-chemical characterization of essential oil produced by hydro-distillation was performed by coupled gas chromatography-mass spectrometer analysis and the antioxidant potential evaluation by in vitro 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity method. ResultsA previously weighed amount of fresh leaves of O. basilicum produced 0.65% of essential oil that led to the identification of a set of 84.44% out of 99.98% as major compounds (> 1.5%). The chemo-type of this essential oil was linalool-methyl chavicol. Chemical components of oil were characterized by oxygenated aromatic hydrocarbons (46.00%) and oxygenated monoterpenes (26.75%). With respect to the amount of components, methyl chavicol also known as estragole (35.72%) constituted the very large quantity afterward linalool (21.25%) and then epi-α-cadinol (8.02%), α-bergamotene (6.56%), eugenol (4.60%), 1,8-cineole (4.04%), germacrene D (2.06%), thymol (1.64%), and (E)-citral (1.55%), respectively. Essential oil exhibited antioxidant potential and IC50 = (1.180 ± 0.015) mg/mL. Non-polar crude extracts yields were low compared to the one of polar extracts. Only methanol and ethyl acetate had considerably manifested antioxidant potential with IC50 values equal to (0.025 ± 0.013) mg/mL and (0.085 ± 0.012) mg/mL, respectively. As concerns to IC50 values, essential oil was less active than methanol and ethyl acetate extracts. The methanol crude extract exhibited the highest activity. Non-polar extracts showed insignificant radical scavenging ability that did not allow assessing IC50 values. These results highlighted the occurrence of antioxidant potential compounds in polar media. ConclusionsEssential oil and crude extracts of O. basilicum growing in DR Congo can be advocated as natural sources of antioxidant potential compounds not only in food but also in pharmaceutical industries. The high antioxidant potential of polar crude extracts highlights antioxidant character of its composition particularly butyl stearate and rosmarinic acid we isolated and identified, respectively in the methanol crude extract.