Comparative studies on the antimicrobial activity of extracts of Chinese medicinal plant Panax notoginseng and native Australian plant Eucalyptus globulus

Author: P Tinusha Paramananthan

Paramananthan, P Tinusha, 2021 Comparative studies on the antimicrobial activity of extracts of Chinese medicinal plant Panax notoginseng and native Australian plant Eucalyptus globulus, Flinders University, College of Medicine and Public Health

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A number of plants have been used as an essential source of medicinal agents for centuries, such as remedies for human diseases, as they produce a diverse range of bioactive molecules. Today’s modern drugs are predominantly obtained from semi-synthetic derivatives of natural products, while a small number are derived directly from natural plant sources used in traditional medicines. According to the World Health Organization (WHO), medicinal plants play a key role in health care; about 60-90% of the world’s population depend traditional medicine. In addition, adverse side effects and high cost are commonly associated with synthetic antibiotics, such as allergic reactions, immunosuppression and hypersensitivity which are becoming increasingly major issues in treating infectious diseases due to long-term and persistent overuse. In the present scenario, researchers are increasingly turning their attention to develop these issues spawned research into utilising the large defence arsenal developed by plants for the development of novel better antibacterial drugs, which may be cheaper and less prone to elicit bacterial resistance. The Eucalyptus globulus leaves and Panax notoginseng roots were used in shaking-assisted extraction in 100% methanol while microwave-assisted extraction used water as a solvent. The antimicrobial activity of the Eucalyptus globulus at a concentration of 5 mg/mL and Panax notoginseng at a concentration of 10 mg/mL was evaluated using a well diffusion method against two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus and Bacillus pumilus). Synergistic effects between crude plant extracts and the antibiotics Gentamycin and Streptomycin were also assessed using a well dilution method. The minimum inhibitory concentration (MIC) was also determined using dilutions. While higher yields were obtained with MAE (22.0%) compared to SAE (16.2%), SAE extracts had a higher antimicrobial and synergistic effect activity compared to MAE extracts. Panax notoginseng failed to show any antimicrobial activity. The E. globulus extract does not show synergy with Gentamicin and Streptomycin. Biochemical compounds of the crude extracts exerting antimicrobial were determined using HPLC. In conclusion, shaking assisted extraction (SAE) of the native Australian plant Eucalyptus globulus could serve as an alternative source for the development of novel therapeutic drugs.

Keywords: Eucalyptus globulus, Panax notoginseng, Shaking-assisted extraction, Microwave-assisted extraction, Gentamicin, Streptomycin

Subject: Biotechnology thesis

Thesis type: Masters
Completed: 2021
School: College of Medicine and Public Health
Supervisor: Associate Professor Kirsten Heimann