Assessment of Copper, Manganese, Potassium and Zinc Levels in Tea Leaves and Their Infusions

Abstract

Macrominerals and microminerals serve as electrolytes, metabolic regulators and also have a structural function in the human body. Deficiency of essential elements may lead to a list of healthy complications which includes growth impairments, birth defects, reduced fertility, weak bones and affected metabolism of lipid, proteins and carbohydrates. Copper is an essential cofactor for collagen and extracellular matrix formation. Zinc plays a critical role in cell division, growth and protein synthesis hence it is important for infants and pregnant women. Delayed wound healing, impaired taste sensitivity; severe deficiency: retarded growth and sexual development and dwarfism are traded some of the signs of zinc deficiencies. Potassium is essential for normal muscular and digestive function, proper functioning of tissues and cells in the human body and also plays a crucial role in heart function, skeletal and smooth muscle contraction. Potassium deficiency in the human body can lead to electrolyte imbalance. Manganese which is a Cofactor of large number of enzymes acts as an antioxidant during normal brain function and animal reproduction. Tea infusions may be a rich source of some macrominerals and microminerals which are essential to human health. Though in trace amounts, these elements are known to play critical roles in various body mechanisms though too much of this elements may also be a health hazard. The tea plant is a perennial evergreen plant with three species i.e. Camellia sinensis, Camellia assamica and Camellia Cambodiensis which is believed to have been dispersed either naturally or by human agencies into tropical and subtropical regions. Tea leaf which is the raw material for tea infusions is composed of different chemical compounds which comprises of caffeine, catechins, volatile compounds, amino acids, trace elements, proteins, and minerals. The aim of this study was to determine the levels of manganese, potassium, zinc and copper elements in tea leaves. Black tea, green tea and purple tea which are the centre of this research are products of the leaves of Camellia Sinensis. During processing of black tea, tea leaves are fully oxidised before being dried. Green tea is a non- fermented product of the leaves from the tea plant and purple tea is a variety that is rich in some specific nutrients. In this study, 24 samples of tea leaves were randomly purchased from selected supermarkets, hawkers and shops in Nairobi Central Business District. The samples were analysed for total potassium, zinc, manganese and copper using Atomic Absorption Spectroscopy (AAS) and Inductively coupled plasma mass Spectrometry (ICP-MS) techniques. The data obtained was interpreted/analysed using the one-way analysis of variance (ANOVA) tool and Kruskal Wallis test under the Statistical Package (STATA) software. The levels of potassium ions in all the tea leaves and their respective tea infusions was significantly higher compared to the levels of manganese, copper and zinc. Levels of copper, manganese, potassium and zinc metal ions in the tea leaves ranged from 41.20 ± 12.47 μg/g to 48.50 ± 19.40 μg/g, 913.6 ± 471.95 μg/g to 1342.10 ± 310.26 μg/g, 12716.30 ± 2541.56 μg/g to 12837.90 ± 3517.60 μg/g and from 111.10 ± 29.98 μg/g to 116.60 ± 20.25 μg/g respectively. Levels of copper, manganese, potassium and zinc metal ions in the tea infusions ranged from 15.1 ± 4.1 μg/g to 43.3 ± 19.9 μg/g, 231.7 ± 3.8 μg/g to 938.2 ± 96.4 μg/g, 5715.4 ± 64.2 μg/g to 16628.7 ± 246.2 μg/g and from 50.6 ± 8.5 μg/g to 144.2 ± 5.9 μg/g respectively. The levels of metal elements in the tea leaves and tea infusions analyzed arranged in the following order: K>Mn>Zn>Cu hence all the three types of tea leaves are reliable sources of potassium and manganese. There was a significant statistical difference in the manganese levels in the three types of tea.