Cordyline terminalis flower is traditionally used to treat asthma and the purple color of the flower is suggestive of anthocyanins. The purpose of this study was to characterize and determine the antioxidant property of anthocyanins from C. terminalis purple flowers. Five anthocyanins, cyanidin 3,5-di-O-β-glucopyranoside (2.6 ± 0.2 mg/g fr. wt) (1), peonidin 3,5-di-O-β-glucopyranoside (2.8 ± 0.3 mg/g fr. wt) (2), cyanidin 3-O-β-(6″-O-E-p-caffeoylglucopyranoside)-5-O-β-glucopyranoside (3.2 ± 0.2 mg/g fr. wt) (3), cyanidin 3-O-β-(6″-O-E-p-coumaroylglucopyranoside)-5-O-β-glucopyranoside (6.2 ± 0.4 mg/g fr. wt) (4), and peonidin 3-O-β-(6″-O-E-p-coumaroylglucopyranoside)-5-O-β-glucopyranoside (9.8 ± 0.2 mg/g fr. wt) (5), were isolated from the flowers of C. terminalis by a combination of chromatographic techniques. Their structures were established by UV-visible, NMR, and ESI-MS. The extract exhibited appreciable antioxidant activity (IC50 ± SD = 13.1 ± 0.8 μg/mL) against quercetin (IC50 ± SD = 4.5 ± 0.4 μg/mL) compared to the individual anthocyanins (IC50 ± SD = 13.8 ± 0.5 to 16.4 ± 0.7 μg/mL) when measured using the 2,2-diphenyl-1-picryl-hydrazyl method. Cordyline terminalis flowers extract may be justified for use and standardization as herbal remedy for asthma.

Urban vegetable farming in wetlands and riverbanks are common features of Ugandan cities. However, urbanization has led to various anthropogenic activities that can lead to the pollution of water resources, enrichment of pollutants in soils and, consequently, pollutant bioaccumulation in edible tissues of plants cultivated on such soils. In this study, we report on the levels of six trace metals (TMTs) in 75 samples of leafy vegetables (Brassica oleracea L., Spinacia oleracea L., Amaranthus hybridus L., Cucurbita pepo L. and Solanum nigrum L.) and soils (n = 75) grown on the banks of River Rwizi, the second longest river in Uganda only after the Nile River. The concentrations of TMTs (Mn, Zn, Cd, Pb, Cr and Cu) in edible vegetable tissues and soils were quantified using flame atomic absorption spectrometry. The mean concentrations (in mg kg⁻¹) of the TMTs in the soil samples were 205–373.84 (Mn), 12.72–65.04 (Zn), 0.26–0.42 (Cd), 3.36–16.80 (Pb), 5.96–25.06 (Cr) and 2.83–35.27 (Cu). In vegetable samples, the concentrations ranged from 43.25 to 110.00 (Mn), 1.08 to 1.83 (Cd), 41.06 to 71.20 (Zn), 4.31 to 6.16 (Pb), 0.65 to 0.81 (Cr) and 5.70 to 14.35 (Cu). With the exception of Mn and Cr, the rest of the TMTs were bioaccumulated in the edible vegetable tissues (bioconcentration factors = 1.03 to 10.71). Considering chronic daily intake through ingestion, dermal contact and inhalation of the TMTs in soils from the banks of River Rwizi, there are no potential non-cancer and carcinogenic health effects that could be experienced in both adults and children. Consumption of leafy vegetables could pose both non-cancer health risks (from ingestion of Zn, Pb, Cr, Mn and Cd) and cancer health risks (due to intake of Cd) in both children and adults. There is therefore a need to enforce regulations to mitigate the pollution of River Rwizi for a more sustainable economic development.

By the time of this study, Kiteezi landfill was Uganda’s largest waste disposal site and received substantial volumes of municipal solid waste. In the present study, water (n = 36), leachates (n = 36), superficial sediments (n = 30), and Colocasia esculenta corms (n = 6) were sampled from Kiteezi landfill in the dry and wet seasons of 2022 before its tragic collapse in 2024. The physicochemical parameters (pH, electrical conductivity, temperature, and oxidation–reduction potential) and concentration of potentially toxic elements (As, Cu, Cr, Pb, and Zn) were analyzed using standard methods and inductively coupled plasma-optical emission spectrometry, respectively. Significant seasonal variations (p < 0.05) were observed for all the physicochemical parameters of water and leachates except temperature. Further, significantly higher concentrations (p < 0.05) of potentially toxic elements (PTXEs) were quantified in environmental matrices sampled during the dry season than the wet season. Arsenic and Pb concentrations in water surpassed their WHO permissible limit of 0.01 mg/L. The concentrations of PTXEs were higher in downstream samples (p < 0.05), indicating that landfill activities led to their enrichment in matrices near the facility. Ecological and pollution risk indices indicated that there is severe enrichment of Cu and Zn in the sediments, with dry season downstream samples having contamination factors and geoaccumulation indices of 539.3 and 74.7 and 8.5 and 5.6, respectively. Although ingestion of water may not cause probable health risks, consumption of Colocasia esculenta corms could lead to non-carcinogenic and cancer health risks in both children and adults (hazard indices = 0.085–189.0 and total cancer risk values of 7.33 × 10⁻⁶–4.87 × 10⁻³). These results emphasize the need that any new replacement for Kiteezi landfill should be properly planned and managed to mitigate potential environmental pollution with xenobiotics.