Elemental composition determination in medicinal plants by neutron activation analysis

Abstract

The use of medicinal plants in the prevention and treatment of diseases is mainly due to its low costs, ease acquisition and cultural aspects. In addition, the absence of its side effects when compared with synthetic drugs and the belief that plants that are natural origin do not cause harmful effects to the organism have stimulated their uses. However, medicinal plants may contain excess essential elements as well as the toxic ones that even in low concentrations are dangerous to human health. The objective of this study was to analyze medicinal plants: Aloe vera (Babosa), Morus nigra sp. (Amoreira) and Moringa oleifera (Moringa) for further correlation studies of the chemical elements with their therapeutic activities. The analytical method used was neutron activation analysis (NAA). The leaves of Aloe vera and Morus nigra were collected in different localities and that of Moringa oleifera were acquired in a store of natural products. Sample preparation consisted of cleaning, drying and milling the leaves. Aliquots of the samples and synthetic element standards were irradiated for 16h under thermal neutron flux of 5 1012 n cm􀀀2 s􀀀1 of the nuclear reactor IEA-R1. The induced gamma activities were measured using a gamma ray spectrometer coupled to a HPGe detector. The radioisotopes formed were identified by half-lives and gamma ray energies. Element concentrations were calculated by comparative method. Quality of the results was evaluated by analyzing certified reference materials INCT-TL-1 Tea Leaves and INCT-MPH-2 Mixed Polish Herbs and the results showed good precision and accuracy. Elements Ca and K were obtained at high concentrations in the plants at the percentage levels. Calcium exhibits neutralizing action and avoids stomach lesions and K has a diuretic action. Elements Br, Fe, Na, Rb and Zn were found in the order of g g􀀀1, and As, Co, Cr, Cs, La, Sb and Sc at lower concentrations, in the order of ng g􀀀1. The Aloe Vera plant presented high concentration of Zn and this element is present in healing remedies. Molibdenum was detected in Moringa oleifera sample and this element is considered essential in many enzymatic processes of the organism. Toxic elements such as Cu and Cd were not detected and As and Sb were found but at very low concentrations. Results obtained in this work indicate the possibility of applying NAA in the correlation studies between the elements present in the plants and their therapeutic effects.