Phytochemical and Heavy Metal Profiles of Foreign and Exotic Apples Sold in Port Harcourt, Nigeria

Apples are among the most widely consumed fruits globally due to their nutritional value and abundance of bioactive compounds. However, environmental contamination, agricultural practices, transportation, and storage conditions may influence both their phytochemical composition and heavy metal accumulation, thereby affecting their nutritional quality and safety. This study assessed the phytochemical constituents and heavy metal concentrations of foreign and exotic apples marketed in Port Harcourt Metropolis, Rivers State, Nigeria. A laboratory-based cross-sectional study was conducted between July and December 2025 in two major fruit markets within Port Harcourt Metropolis (Kaduna Street Fruit Garden Market and Ogbunabali Fruit Market). A total of sixteen (16) apple samples comprising foreign and exotic varieties were collected and analyzed. Standard phytochemical analytical procedures were employed to determine the concentrations of alkaloids, flavonoids, glycosides, oxalates, saponins, and tannins. Heavy metal concentrations, including copper (Cu), chromium (Cr), cadmium (Cd), and lead (Pb), were determined using Atomic Absorption Spectrophotometry (AAS) following acid digestion. Data were analyzed using SPSS version 27, and results were expressed as mean ± standard deviation. Statistical significance was set at p < 0.05. Foreign apples exhibited higher concentrations of alkaloids (94.89 ± 1.15 mg/kg and 84.55 ± 0.52 mg/kg), saponins (33.77 ± 0.57 mg/kg and 33.72 ± 0.49 mg/kg), and glycosides (21.80 ± 0.80 mg/kg and 18.68 ± 0.07 mg/kg) across the two sampling stations. Conversely, exotic apples contained higher flavonoid concentrations (65.24 ± 0.14 mg/kg and 75.48 ± 0.54 mg/kg) and tannins at Station 2 (85.55 ± 0.32 mg/kg). Oxalate levels remained relatively low in all samples. Heavy metal analysis revealed consistently higher concentrations of copper, chromium, cadmium, and lead in foreign apples compared with exotic apples. Cadmium concentrations in foreign apples at Station 2 (0.30 ± 0.015 mg/kg) exceeded the recommended international safety limit of 0.20 mg/kg, while lead concentrations in both apple varieties exceeded the permissible limit of 0.05 mg/kg. Significant differences were observed between apple types and sampling locations for most phytochemical and heavy metal parameters (p < 0.05). Both foreign and exotic apples marketed in Port Harcourt possess valuable phytochemical constituents that may contribute to their nutritional and health-promoting properties. However, the elevated concentrations of cadmium and lead detected in some samples raise important food safety concerns. Routine monitoring of heavy metal contamination in fruits, strengthened quality control measures, and improved agricultural and post-harvest handling practices are recommended to ensure consumer safety and maintain fruit quality.