An Overview on Manganese in Nature

摘要

Manganese is the most 12~(th) prevalent element on Earth that occurs in 11 oxidation states (from -3 up to +7). An essential element present in all living organisms, manganese is required for growth, development and maintenance of health. It is naturally present in soil, plants, water.In soil, it occurs as exchangeable manganese, manganese oxide, organic manganese and a component of ferromagnesian silicate minerals. The amount of available manganese is mostly influenced by soil reaction, organic matter content, moisture and soil reaction.In plants, it activates a large number of enzymes that catalyzes oxidation-reduction processes, decarboxylation, fatty acids synthesis or hydrolysis. Plants absorb divalent form of manganese from soil solution. Mn~(+2) suffer easily an oxidation process to Mn~(+3 )and Mn~(+4) and due to this behavior are involved in redox processes.Manganese deficiencies appear usually on acidic soils, low in native Mn or soil with pH above 6.5, poorly drained calcareous soils and organic matter rich. Symptoms of manganese deficiency include interveinal chlorosis with dark-green veins.In human body, the role of manganese as co-factor for enzymes represent one of the most important functions of this element. Mn-dependent enzymes are oxidoreductases, transferases, hydrolases, lyases, isomerases, meanwhile manganese metalloenzymes include arginase, glutamine-synthetase, phosphoenolpyruvate decarboxylase, Mn-superoxide dismutase. Manganese deficiency in humans is uncommon, but high levels lead to manganism with manifestations similar to Parkinson disease (generalized bradykinesia and widespread rigidity). Unlike idiopathic Parkinson’s disease, patients with manganism may have a less frequent resting tremor, more frequent dystonia, easily fall backward and failure to respond to levodopa.The uses of manganese are manifold and include steel production, production of potassium permanganate, glass, textile bleaching. Manganese coordination compounds present antimicrobial properties or are used in magnetic resonance image of the liver.Taking into account that manganese presents a significant role for plants and human beings, this paper present a review of literature that illustrates the importance of manganese.