Comparative analysis of essential oil composition and oil containing glands in Ocimum sanctum L. (Holy basil) under ambient and supplemental level of UV-B through gas chromatography–mass spectrometry and scanning electron microscopy

Field grown plants of holy basil (Ocimum sanctum L.) were treated with biologically effective supplemental ultraviolet-B (sUV-B) radiation (ambient +1.8 kJ m−2 day−1) to evaluate its effect on specialized oil glands and quantity and quality of the essential oil. The total yield of essential oil increased significantly by 42.0% after sUV-B treatment. Gas chromatography–mass spectrometry analysis showed that most important flavor compounds β-caryophyllene, germacrene-D, ethyl linoleolate, β-elemene and camphenol increased significantly after sUV-B treatment. Moreover, the level of main compound eugenol was not affected significantly. Scanning electron microscopy analysis showed turgidity of oil glands after sUV-B exposure and it was well correlated with the higher yield of essential oil. The result is of specific interest because if other parameters remain constant, sUV-B may affect the production of the essential oil in Ocimum sanctum L.