Effect of cadmium and aluminum on growth, metabolite content and biological activity in Drimia elata (Jacq.) Hyacinthaceae

• Drimia elata is one of the most frequently utilized bulbous medicinal plants in South Africa traditional medicine
• Uptake and accumulation of cadmium and aluminium in Drimia elata (Jacq.) is of safety concern for the consumer
• Plants exposed to Cd and Al treatments exhibited high levels of proline accumulation and a marked reduction in plant biomass
• High levels of Cd and Al negatively affect the quality D. elata by reducing the amounts of phytochemical content
• Poor antimicrobial activity was recorded at high levels of Cd and Al in D. elata

Drimia elata (Jacq.) is a bulbous plant that is extensively utilized in South African traditional medicine. This study investigated the effects of cadmium (Cd) and aluminum (Al) on growth, heavy metal bioaccumulation, metabolite content and antibacterial activity in D. elata. Seeds were germinated and after seven months, plants were exposed to various concentrations of Cd and Al both singly and in combinations for six weeks. Thereafter, the experiment was terminated and the mean fresh (FW) and dry weights (DW) of the bulb and shoot biomass recorded. Dried samples (0.5 g DW) were analyzed for Cd and Al accumulation using Inductively Coupled Plasma-Optical Emission Spectroscopy. In addition, total chlorophyll, free-proline, total phenolic and flavonoid content were quantified as a measure of plant stress. Antibacterial activity was assessed using the microdilution assay and the activity was correlated to heavy metal and secondary metabolite content. Plants exposed to heavy metals generally exhibited a marked reduction in plant biomass. The highest Cd content (83 mg/kg) was recorded in bulbs grown in Cd 5:Al 1000 mg/l. There was a significant increase in free-proline and a significant reduction in the chlorophyll, phenolic and flavonoid content in plants exposed to increasing concentrations of Cd and Al. This decrease in secondary metabolite content may account for the poor antibacterial activity of plants grown in most of the heavy metal treatments. This results indicate that exposure of D. elata to heavy metal contaminated soil may potentially compromise the health of the consumer due to heavy metal bioaccumulation as well as reduced efficacy of the herbal product.