Effects of different drying methods on the proximate composition and antioxidant activities of ocimum basilicum leaves

Abstract

Two different drying methods-freeze drying and vacuum oven drying were applied to Ocimum basilicum leaves to determine the proximate composition and antioxidant activities. The results were compared to fresh leaves of Ocimum basilicum. Each sample was prepared for determination in three different solvents-methanol, ethanol, and water have been used. The total phenolic content (TPC) and total flavonoid content (TFC) assays showed almost the same values in the freeze-dried sample of methanol extract as it exhibited the highest TPC and TFC values-54.46±1.24 mg gallic acid/g, 950±17.32 mg quercetin/g whereas the water extract showed only 26.23±0.63 mg gallic acid/g and 543.33±56.86 mg quercetin/g, respectively. On the contrary, fresh sample with water extract displayed the lowest TPC and TFC. In addition, the percent inhibition of 1,1-diphenyl-2-2picrylhydrazyl (DPPH) free radical-scavenging assay ranged from 6.09± 0.47% in fresh sample with water extract to 92.60±0.58% in freeze-dried sample with methanol extract. The ferric reducing antioxidant power (FRAP) assay values ranged from 7.62±1.09 µmol FeII/g in fresh samples with water extract to 1,160.95±15.80 µmol FeII/g in freeze-dried sample with methanol extract. Both assays showed the same trend of result with the highest antioxidant activity observed in freeze-dried sample with methanol extract and the lowest from fresh samples with water extract.