Israt J Biva1, Chi P Ndi2, Hans J Griesser3, Susan J Semple4. 1. Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia; Wound Management Innovation Cooperative Research Centre, Toowong, QLD 4066, Australia. Electronic address: Israt.Biva@mymail.unisa.edu.au. 2. Quality Use of Medicines and Pharmacy Research Centre, Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Frome Road, Adelaide, SA 5000, Australia. Electronic address: Chi.Ndi@unisa.edu.au. 3. Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia; Wound Management Innovation Cooperative Research Centre, Toowong, QLD 4066, Australia. Electronic address: Hans.Griesser@unisa.edu.au. 4. Quality Use of Medicines and Pharmacy Research Centre, Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Frome Road, Adelaide, SA 5000, Australia. Electronic address: Susan.Semple@unisa.edu.au.
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE: For traditional medicinal purposes Aboriginal Australians have utilised numerous plant species, Eremophila alternifolia is among the most prominent. Traditionally, fresh leaves, leaf-infusions and handmade leaf-pastes have been used as both external and internal preparations to provide relief from a variety of conditions. Preparations of the species have been used to treat various infections of skin, eyes and throat including the treatment of septic wounds. These usages suggest that the plant contains antibacterial compounds; however, to date they have not been isolated and identified. AIM OF THE STUDY: The present study aimed to identify antibacterial compounds from this important traditionally recorded medicinal species. MATERIALS AND METHODS: Bioassay-guided fractionation was used to isolate compounds from the crude leaf-extract. Antibacterial activity of pure compounds was assessed through broth microdilution method by determining both minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). Structure elucidation was performed using spectroscopic techniques such as 1D and 2D nuclear magnetic resonance spectroscopy and high resolution mass spectrometry. RESULTS: Four compounds have been isolated from the leaf-extract; they include previously known flavanones [pinobanksin (1), pinobanksin-3-acetate (2) and pinobanksin-3-cinnamate (3)] and a serrulatane diterpene, 8-hydroxyserrulat-14-en-19-oic acid (4). While compound 4 had been found in other Eremophilas, flavanones 2 and 3 are identified for the first time from the genus Eremophila. The flavanone 3 is the most promising antibacterial compound with significant activity (10-20µM) against strains of the Gram-positive bacterium Staphylococcus aureus including methicillin resistant and biofilm forming strains. No activity was observed for any isolated compounds against the Gram-negative bacterium Escherichia coli. CONCLUSION: The antibacterial activity of the crude extract of E. alternifolia and of the isolated compounds against Gram-positive bacteria provides a Western scientific explanation of the therapeutic modality of this plant species in traditional Aboriginal medicinal practice.
ETHNOPHARMACOLOGICAL RELEVANCE: For traditional medicinal purposes Aboriginal Australians have utilised numerous plant species, Eremophila alternifolia is among the most prominent. Traditionally, fresh leaves, leaf-infusions and handmade leaf-pastes have been used as both external and internal preparations to provide relief from a variety of conditions. Preparations of the species have been used to treat various infections of skin, eyes and throat including the treatment of septic wounds. These usages suggest that the plant contains antibacterial compounds; however, to date they have not been isolated and identified. AIM OF THE STUDY: The present study aimed to identify antibacterial compounds from this important traditionally recorded medicinal species. MATERIALS AND METHODS: Bioassay-guided fractionation was used to isolate compounds from the crude leaf-extract. Antibacterial activity of pure compounds was assessed through broth microdilution method by determining both minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). Structure elucidation was performed using spectroscopic techniques such as 1D and 2D nuclear magnetic resonance spectroscopy and high resolution mass spectrometry. RESULTS: Four compounds have been isolated from the leaf-extract; they include previously known flavanones [pinobanksin (1), pinobanksin-3-acetate (2) and pinobanksin-3-cinnamate (3)] and a serrulatanediterpene, 8-hydroxyserrulat-14-en-19-oic acid (4). While compound 4 had been found in other Eremophilas, flavanones 2 and 3 are identified for the first time from the genus Eremophila. The flavanone 3 is the most promising antibacterial compound with significant activity (10-20µM) against strains of the Gram-positive bacterium Staphylococcus aureus including methicillin resistant and biofilm forming strains. No activity was observed for any isolated compounds against the Gram-negative bacterium Escherichia coli. CONCLUSION: The antibacterial activity of the crude extract of E. alternifolia and of the isolated compounds against Gram-positive bacteria provides a Western scientific explanation of the therapeutic modality of this plant species in traditional Aboriginal medicinal practice.
Authors: Oliver Gericke; Rachael M Fowler; Allison M Heskes; Michael J Bayly; Susan J Semple; Chi P Ndi; Dan Staerk; Claus J Løland; Daniel J Murphy; Bevan J Buirchell; Birger Lindberg Møller Journal: Plant J Date: 2021-09-16 Impact factor: 7.091
Authors: Susan J Semple; Dan Staerk; Bevan J Buirchell; Rachael M Fowler; Oliver Gericke; Louise Kjaerulff; Yong Zhao; Hans Albert Pedersen; Malene J Petersen; Line Fentz Rasmussen; Emilie Kold Bredahl; Gustav Blichfeldt Pedersen; Laura Mikél McNair; Chi P Ndi; Nikolaj Lervad Hansen; Allison M Heskes; Michael J Bayly; Claus J Loland; Nanna Heinz; Birger Lindberg Møller Journal: Plant J Date: 2022-07-23 Impact factor: 7.091