Available in print form, Tunguu reference libraryThe levels of selected elements in Hibiscus sabdariffa calyces and Lippia asperifolia leaves were determined for possible effects on human blood pressure. The aim was to determine the levels of selected elements in each species, and comparing their iron level along with investigation of their possible effects on human blood pressure. Ten samples each for Hibiscus sabdariffa calyces and Lippia asperifolia leaves were collected from Bububu and Mtoni and from Kombeni and Fuoni respectively, these areas are allocated within the western district of Unguja, Zanzibar. The X-ray fluorescence method of analysis was used using EDXRF equipment at TAEC, Arusha, Tanzania with sub-ppm level detection limits. The findings revealed that, L. asperifolia leaves contained (2641 – 2161 mg/Kg) of Na, (3274 – 1282 mg/Kg) of Fe, (9134 – 8466 mg/Kg) of Ca, (3050 – 1549 mg/Kg) of P, (241.2 – 146.9 mg/Kg) of Mn, (6635 – 5872 mg/Kg) of K, (23.9 – 20.37 mg/Kg) of Zn, (5205 – 3616 mg/Kg) of Mg and (9.869 – 8.963 mg/Kg) of Cu. While H. sabdariffa calyces contained (1984 – 1399 mg/Kg) of Na, (933.4 - 703.3 mg/Kg) of Fe, (7231 – 6315 mg/Kg) of Ca, (1986 – 993.5 mg/Kg) of P, (404.6 – 309.1 mg/Kg) of Mn, (8239 – 7343 mg/Kg) of K, (38.36 – 26.62 mg/Kg) of Zn, (5021 – 2923 mg/Kg) of Mg and (6.283 – 4.339 mg/Kg) of Cu. Similarly, their effects on human blood pressure were investigated. Fifty people, each one was given with 300 mL of the extracted juice of the plant species for oral intake. Their blood pressure was recorded at 30-minute intervals, using clinically validated Blood Pressure arm monitor. The results obtained had shown remarkable drop of both SBP and DBP. Moreover, the findings suggest that the juices might have raised the haemoglobin level due to the presence of high levels of iron.