PRELIMINARY PHYTOCHEMICAL SCREENING, QUALITY ASSESSMENT AND MINERAL CONTENT DETERMINATION OF SELECTED BRANDS OF GREEN TEA MARKETED IN ZARIA, NIGERIA

PRELIMINARY PHYTOCHEMICAL SCREENING, QUALITY ASSESSMENT AND MINERAL CONTENT DETERMINATION OF SELECTED BRANDS OF GREEN TEA MARKETED IN ZARIA, NIGERIA

Abstract:

Green tea in its purest and most unadultered form has always influenced human health for generations. Though green tea is not officially recognized as a medical agent, it is one of the most researched plant-based remedies with possible benefits including antioxidant activity, skin protection, oral health, good vision, help combat obesity, antiviral potential and many more. This study was aimed at assessing the preliminary phytochemical screening, quality assesment and mineral content determination of selected brands of green tea marketed in Zaria. Quality assessment was conducted on twelve selected brands of green tea marketed in Zaria. Identification test, uniformity of weight, moisture content, total ash values, water soluble ash and acid insoluble ash were determined using official methods. Preliminary phytochemical screening of the samples was conducted according to standard method. A rapid, simple, precise and accurate UV spectrophotometry method for analysis of Epigallocatechin gallate (EGCG) in green tea at 274 nm was developed and validated based on ICH guideline. Calibration curve was constructed within the range of 2.0 to 10.0 μg/ml, and the developed method was employed to quantify EGCG in the various brands of green tea. The EGCG content ranged from 0.75 – 0.82 mg/g, with three samples having significantly higher values (p < 0.05) than the rest. Essential trace metals (Fe, Zn and Cu) and other heavy metals (Pb and Cd) were analysed in the green tea samples. All the green tea brands passed uniformity of weight test as their percentage deviations were less than 7.5 %. The moisture content of the samples range from 1.6 – 14.35 %, with the percentages in eight samples been significantly higher (p < 0.05) than the NAFDAC limit (8 %). The total ash values of the samples range from 5 to 12.50 %; seven of the samples were significantly different (p < 0.05) from the IARC-WHO limit (4 – 8 %). Similarly, for the water soluble ash range was 1.75 – 6 %, only one of the samples was found to have significantly higher vi percentage (p < 0.05) than the IARC-WHO limit (5 %). The acid insoluble ash range from 1.00 to 4.25 %, with seven of the samples havng significantly higher percentage (p < 0.05) than the IARC-WHO limit (1 %). The phytochemical analysis showed the presence of tannins, saponins, cardiac glycosides, flavonoids, alkaloids, and terpenoids. The wavelength of maximum absorbance of EGCG in water was obtained at 274 nm. The calibration curve obeyed Beers-Lambert law in the concentration range from 2.0 – 10.0 μg/ml with correlation coefficient of 0.998. The precision, accuracy, (% relative error), % recovery, limit of detection and limit of quantitation were determined (1.7 %, 1.99 %, 95.77 %, 0.68 μg/ml and 2.07 μg/ml) respectively. Heavy metals (Fe, Zn, Cu, Pb and Cd) were detected in almost all the samples, with Fe having the highest concentration (164.04 mg/g) recorded and Cd having the lowest concentration (0.02 mg/g) recorded. There was significant difference (p < 0.05) in metal content in all the brands, however, for some brands the metals were below detection limit of the analytical method. Thus, it can be concluded that consumption of all the green tea brands analyzed may be beneficial to human health as a result of the phytochemical and essential metal content, and may also be safe because the toxic metals are within the permissible limits

PRELIMINARY PHYTOCHEMICAL SCREENING, QUALITY ASSESSMENT AND MINERAL CONTENT DETERMINATION OF SELECTED BRANDS OF GREEN TEA MARKETED IN ZARIA, NIGERIA