Chemical constituents, antioxidant and potential allelopathic effect of the essential oil from the aerial parts of Cullen plicata

The intensive use of synthetic chemical pesticides has a serious impact on humans and the environment. The essential oil is a proper class of allelochemicals to be used as bio herbicides due to their biodegradability, high structural diversity and reduced natural resistance to weeds. The essential oil from the aerial parts of Cullen plicata (Delile) C.H. Stirt. was extracted by hydrodistillation and analyzed by gas chromatography/mass spectrometry. A concentrations of 50, 100, 150 and 200 mu L L-1 of the essential oil were prepared for studying their allelopathic activities on germination and seedling growth of Bidens pilosa and Urosperrnum picroides. In addition, the antioxidant activity was investigated. Thirty five compounds were determined, mainly sesquiterpenes (77.14%). The dominant sesquiterpenes are (-)-caryophyllene oxide (33.42%), Z-nerolidol (17.92%), tau.cadinol (9.06%) and a-cadinol (6.66%). At 200 mu L L-1, the germination of both B. pilosa and U. picroides was completely inhibited. The IC50 value of the essential oil on germination inhibition of B. pilosa and U. picroides were 49.39 and 17.86 mu L L-1, respectively. On the other hand, the inhibition seedling growth of both B. pilosa and U. picroides showed significant dose proportional increases in the inhibition under the treatment of the essential oil. However, B. pilosa was strongly inhibited than U. picroides. The antioxidant activity of the C plicata essential oil has IC50 value of 1.31 mu L mL(-1) compared to 0.03 mu L mL(-1) for catechol. From this study, we can say that C plicata essential oil could give a hope toward production of eco-friendly bio herbicides at least against B. pilosa and U. picroides and also as a source of natural antioxidants that could be used as food additives. (C) 2015 Elsevier B.V. All rights reserved.