Gas Chromatography - Mass Spectrometry Analysis and In vitro Antioxidant Activity of the Ethanolic Extract of the Leaves of Tabernaemontana divaricata

Objective: To identify phytoconstituents present in an ethanolic extract of the leaves of Tabernaemontana divaricata and to evaluate its in-vitro antioxidant potential. Methods: The extract was subjected to gas chromatography- mass spectrometry analysis to identify phytoconstituents, and screened for hydroxyl, superoxide and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, reducing power and metal-chelating activity as a measure of potential antioxidant activity. Results: GC-MS analysis of the extract revealed the presence of 96 phytoconstituents, of which 17 are reported to be bioactive and 11 of these to possess antioxidant potential. When tested in-vitro, the extract exhibited the most potent radical-scavenging activity at a maximum concentration of 10 mg/ml, scavenging effects of 64%, 67% and 69% and corresponding half maximal inhibitory concentration (IC₅₀) values of 6.7 mg/ml, 6.8 mg/ml and 6.2 mg/ml on hydroxyl, superoxide and DPPH radicals, respectively. Ascorbic acid used as a standard (10 mg/ml) showed scavenging effects of 73%, 73% and 75% and corresponding IC₅₀ values of 5.3 mg/ml, 5.8 mg/ml and 5.2 mg/ml, respectively, on hydroxyl, superoxide and DPPH radicals. At 10 mg/ml, the extract and an ethylenediaminetetraacetic acid standard exhibited 68% and 78%, respectively, chelation of ferrous ions; at the same concentration, the reducing power of the extract and that of a butylated hydroxytoluene standard was found to be 3.855 and 4.308, respectively. Conclusion: These observations strongly suggest that the ethanolic extract of T. divaricata leaves has potent in-vitro antioxidant activity and thereby could act as a possible therapeutic agent for oxidative stressinduced pathological states.