Untargeted UPLC-Q/TOF-MS-based metabolomics and inductively coupled plasma optical emission spectroscopic analysis reveal differences in the quality of ginger from two provinces in Zambia.

Abstract

This study sought to investigate the differences in the quality of dried ginger samples obtained from two places in Zambia, Lusaka and Copperbelt in terms of their secondary metabolite differences and heavy metals content. Ten and eight batches of dried ginger obtained, respectively, from Lusaka and Copperbelt were analysed using untargeted Q/TOF-MS-based metabolomics and inductively coupled plasma optical emission spectroscopy (ICP-OES). The metabolomics approach yielded 11 differential metabolites that clearly discriminated between the samples from the two locations. Eight were found to be more abundant in the samples from Lusaka while three were present in greater amounts in the samples from Copperbelt. The results of the heavy metal content analysis for four selected elements, Cd, Pb, As and Cu, showed that the samples from Copperbelt recorded higher levels. However, all samples contained levels of the toxic metals, Cd and Pb above permissible limits, making them unwholesome for human consumption. The outcome of the heavy metal content analysis led us to speculate that abiotic stress as a result of these metals experienced by the ginger rhizomes during cultivation could have contributed to the metabolites abundance differences. Further studies are, however, recommended to verify this hypothesis.