Comparative Study of Selected Metals, Total Phenolics and Antioxidant

日期 : Aug 2016 - Sep 2017

Various onion, soil and irrigation water samples were collected form the agricultural areas of Attock, Fatehjang, Lahore, Layyah, Rawalpindi, Vehari and Chitral. The samples were processed for metal analysis using flame atomic absorption spectrometer. Digestion of soil and onion samples was done according to the reported method. The samples were processed to find out the essential and toxic metals along with their phytochemical contents and the antioxidant properties. For phytochemical contents and antioxidant properties dried, powdered onion samples were extracted using methanol. Total phenolic contents and flavonoids were determined along with the evaluation of DPPH radical scavenging activity. Among the metals, K showed highest concentration in the onion samples, followed by Mg, Na and Ca. Most of the trace metals showed random distribution in various onion varieties. Very strong and significant correlations were observed in most of the cases and quartile distribution pattern showed that metals were more dispersed and asymmetrically distributed in the onion and water samples compared to the soil samples. Among phytochemicals, methanol extracts of most of the onion varieties showed exceedingly higher phenolic contents and flavonoid contents. DPPH scavenging activity also showed very high values for the onions; most of the varieties showed values higher than 60%. Among the selected metals, Na, Cd, K, Co, Cr and Pb showed significant bioaccumulation in different onion varieties. Significant anthropogenic contributions of the metals were observed in the onion samples as shown by multivariate statistical methods. Health risk assessment for selected metals in the onions showed that hazard quotient and cancer risk indicated values much below the safe limits (unity and 1 x 10-4, respectively) indicating no long term non-carcinogenic as well as carcinogenic health risks are associated with the consumption of these onion varieties.