Phytosociology and antioxidant profile study for selecting potent herbs for phytoremediation of crude oil-contaminated soils

Crude oil exploration activities affect the surrounding vegetation. The present investigation deals with the study of phytosociology and biochemical profiles of the herbaceous community in the active and abandoned oil drilling sites of crude oil-explored area. For comparison, a similar investigation was also carried out in control sites where oil exploration activities were not evident. At first, a phytosociological investigation was carried out and based on the results obtained antioxidant enzyme profiles of dominant herbs were studied to understand their defense mechanism to crude oil-associated stress. A total of 69 plant species belonging to 20 families were recorded in the studied sites and the family Cyperaceae was the most dominant in the crude oil-contaminated sites. The results revealed that the plants growing near the oil-explored-contaminated sites exhibit a higher level of DPPH and H2O2 radical scavenging activities as compared to control plant samples. For DPPH assay, the lowest IC50 value was exhibited by Cyperus rotundus which was recorded to be 31.49 and 55.31 respectively for the samples of contaminated and control sites. Again, in the case of H2O2 scavenging activity assay, Parthenium hysterophorus showed the lowest IC50 values of 27.48 and 63.07 for the samples of contaminated and control sites respectively. As a whole, the findings confirm the superior defense mechanism of some dominant herbs of the contaminated sites that include Torenia flava, Croton bonplandianus, Eclipta alba, Cyperus rotundus, Cyperus brevifolius, and Parthenium hysterophorus and their suitability for use in phytomanagement practices.