Phytochemical and antioxidant profiling of Ocimum sanctum

The leaves of Ocimum sanctum were extracted in methanol (OsM) and sequentially fractionated with n-hexane (OsH), ethylacetate (OsE) and butanol (OsB) to find the best extraction solvent for antioxidants from the herb known for its medicinal values. OsB was rich in both total polyphenolic content (TPC) (212.26 ± 6.3 mg GAE/g extract) and total flavonoid contents (TFC) (54.51 ± 3.5 mg QE/g extract). OsE also had significantly high TPC (202.71 ± 5.5 mg GAE/g extract). The EC₅₀ based on DPPH (3.91 ± 0.3 μg/ml), ABTS (1.6 ± 0.1 μg/ml) and phosphomolybdate (2.31 ± 0.1 μg/ml) for OsB; hydroxyl (5.3 ± 0.4 μg/ml), superoxide (7.32 ± 0.9 μg/ml) radicals for OsM and DPPH (8.61 ± 0.6 μg/ml), phosphomolybdate (2.43 ± 0.1 μg/ml) and ABTS (5.3 ± 0.4 μg/ml) for OsE were lower than ascorbic acid showing potential antioxidant properties. EC₅₀ values of different fractions for DPPH anion, ABTS cation free radical scavenging and phosphomolybdate reducing property were significantly and positively correlated with TPC and TFC. LC-MS analysis of OsB and OsE showed the presence of luteolin, apigenin, rosmarinic, chlorogenic, caffeic acid and their derivatives. Quercetin is extracted in ethylacetate fraction. Overall data revealed that O. sanctum leaf extracts in butanol and ethylacetate with high polyphenolics and flavonoids, had strong antioxidant potential.