Chemical Constituents and Antioxidant Capacity of Ocimum basilicum and Ocimum sanctum

The chemical constituents of leaves, inflorescence, and flowers from Ocimum basilicum (Thai basil) and Ocimum sanctum (Holy basil) were analysed by gas chromatography-mass spectrometry. The chemical compounds were extracted by hydrodistillation, headspace-solid phase microextraction, and solvent extraction.  The main constituents of Ocimum basilicum were identified to consist of estragole (> 35.71%), (E)-β-ocimene (> 1.47%), trans-α-bergamotene (> 0.83%), τ-cadinol (> 0.41%) eucalyptol (> 0.25%) and α-caryophyllene (> 0.07%) while Ocimum sanctum consists mainly of eugenol methyl ether (> 34.34%), (E)-caryophyllene (> 7.91%), germacrene D (> 5.58%), β-elemene (> 4.22%) and copaene (> 1.49%).  Ocimum basilicum and Ocimum sanctum leaves contain more chemical constituents followed by inflorescence and flowers. The genetic distance between the two species was calculated to investigate the interspecies relationship and it is 2.86. The calculated genetic distance between the two species showed that Ocimum basilicum and Ocimum sanctum are closely related species and share some of the same traits.  The methanol and dichloromethane extracts of Ocimum basilicum leaves showed an IC50 value of 88 μg/mL and 1178 μg/mL, respectively, while the methanol and dichloromethane extract of Ocimum sanctum showed a higher 2, 2-diphenyl-1-picrylhydrazil free radicals scavenging activities with an IC50 value of 11 μg/mL and 369 μg/mL, respectively. The natural antioxidant level Ocimum sanctum and Ocimum basilicum indicated that they can be used effectively in food preservation.