Regnier, TC, Kouekam, CR, Leonard, CM, Mokgalaka, NS & Weiersbye, IM 2009, 'Chemical analysis and potential use of the tree Combretum erythrophyllum grown on gold and uranium mine tailings seepage', in AB Fourie & M Tibbett (eds), Mine Closure 2009: Proceedings of the Fourth International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 539-547, https://doi.org/10.36487/ACG_repo/908_42
(https://papers.acg.uwa.edu.au/p/908_42_Regnier/)
Abstract: Combretum erythrophyllum is a southern African riparian tree, which is widely used in traditional medicine 
to combat microbial infections. More than seven flavonoids with antimicrobial properties, including 
apigenin, genkwanin, rhamnocitrin and kaempferol, have been previously isolated from methanolic extracts 
of leaf material. The species occurs naturally in the Witwatersrand Basin gold fields, and is included in 
experimental trials of acid and salt-tolerant trees for seepage control purposes around gold mine tailings at 
AngloGold Ashanti Ltd (the Mine Woodlands Project). In this study, C. erythrophyllum, harvested from the 
mine woodland trials, was investigated as a source of secondary metabolites for the control of food-borne 
pathogens. The phenolic profiles of methanolic leaf extracts from trees growing on acid mine drainage and 
non-impacted surrounding soils were compared to those from a natural population, using high performance 
liquid chromatography. The concentrations of apigenin, genkwanin and kaempferol are currently being 
determined in dry leaf material. These extracts were evaluated for their ability to inhibit the growth of 
Listeria monocytogenes and Candida albicans biofilm formation. No significant differences between the 
phenolic profiles of samples from different substrata or regions could be discerned. Selected extracts of both 
mine and natural populations were able to significantly inhibit biofilm formation in the case of C. albicans. 
The activity against L. monocytogenes was substantially lower. Micrographs obtained using confocal laser 
scanning microscopy confirmed the inhibitory effects. These results demonstrate the potential of  
C. erythrophyllum as a good candidate for application in food safety. Such commercial attributes can add 
value to C. erythrophyllum and other species used for mine rehabilitation, and provide a basis for the 
development of secondary industries based on renewable natural resources alongside mine closure.