Screening of Selected Herbs for Their Antioxidant and Antimicrobial Properties

Lim, Hock Leong (2016) Screening of Selected Herbs for Their Antioxidant and Antimicrobial Properties. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

In recent years, there has been more pressure to use natural preservatives in preservation of foods as the use of other synthetic preservatives might cause harm to the consumer in the long run. In this study, 6 selected herbs were chosen to screen for their antioxidant and antimicrobial properties. The microorganisms selected were E. coli, L. monocytogenes, P. aeruginosa, S. typhi and S. aureus. The herbs chosen were Bay leaves (Laurus nobilis), Basil (Ocimum basilicum), Oregano (Origanum vulgare), Parsley (Petroselinum crispum), Rosemary (Rosmarinus officinalis) and Thyme (Thymus vulgaris). The Total Phenolic Content (TPC) antioxidant test was measured in terms of gallic acid equivalent (GAE) per gram of extract, Oregano sample had 9.349 GAE/g±0.01401, Bay sample had 4.835GAE/g±0.01059, Thyme sample had 8.291GAE/g±0.005297, Parsley sample had 2.852GAE/g±0.009174, Rosemary sample had 6.227GAE/g±0.01401, and Basil sample had 9.009GAE/g±0.01401. For the DPPH antioxidant test the results were measured in percent inhibition, Oregano sample had 90.3885%±0.1561, Bay sample had 90.8998%±0.05903, Thyme sample had 89.7750%±0.1181, Parsley sample had 38.3436%±0.1022, Rosemary sample had 90.7975%±0.2044, and Basil sample had 90.2863%±0.1181. The disc diffusion test was measured in diameter, Oregano sample had 7mm for both L. monocytogenes and P. aeruginosa, Bay sample had 6mm for E. coli, 5mm for both L. monocytogenes and S. aureus and 4mm for P. aeruginosa, Thyme sample had 5mm for both E. coli and P. aeruginosa, and 8mm for S. aureus, Parsley sample had 9mm for L. monocytogenes and 7mm for P. aeruginosa, Rosemary had 7mm for E. coli, 8mm for L. monocytogenes, and 9mm for S. aureus, Basil sample had 10mm for L. monocytogenes. For Minimum Inhibitory Concentration (MIC) test, at 83mg/ml Oregano inhibited L. monocytogenes and P. aeruginosa, at 83mg/ml Bay inhibited E. coli, L. monocytogenes, S. aureus and P. aeruginosa, at 83mg/ml Thyme inhibited E. coli, S. typhi, S. aureus and P. aeruginosa, at 83mg/ml Parsley inhibited L. monocytogenes and P. aeruginosa, at 83mg/ml Rosemary inhibited E. coli, L. monocytogenes and S. aureus, at 83mg/ml Basil inhibited L. monocytogenes.