Extraction optimization for Murraya koenigii leaves with high antioxidant and antibacterial properties

Murraya koenigii or commonly known as curry tree is an aromatic shrub in the family Rutaceae. The tree can be found in a tropical to sub-tropical regions and people use it for centuries in cooking, and ethnomedicinal purposes in traditional remedy. This study was focused to investigate the effects of ethanol concentration and solid to liquid ratio on the M. koenigii leaf extraction to obtain high total phenolic content (TPC) with high antioxidant and antibacterial properties. The extraction was carried out in a reflux system at three different solid to liquid ratios, namely 1:5, 1:10 and 1:20, in two different ethanol concentrations, which were 75% and 99% ethanol. The other fixed extraction conditions were set at 50°C for one hour. The antioxidant activity of M. koenigii leaf extracts were determined using the colorimetric DPPH radical scavenging assay, and recorded the highest antioxidant activity with the IC50 0.517mg/ml from the 1:5 solid to liquid ratio in 75% ethanol. This ratio also produced the highest TPC 51.04 mg GAE/g dried extract. The optimized leaf extract was then analysed for its antibacterial properties against Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli with significant inhibitory actions at the minimum inhibition concentration, 2.708 mg/ml, 0.338 mg/ml, and 5.415 mg/ml, respectively. This study showed that ethanol 75% with solid to liquid ratio of 1:5 had the highest antioxidant and TPC content respectively. The data obtained implicated that an increased phenolic content in M.koenigii leaves extracts proportionally increases their antioxidant efficiency