Mineral and Trace Element Concentrations in Morinda citrifolia L. (Noni) Leaf, Fruit and Fruit Juice

摘要

Fruit and leaf of noni (Morinda citrifolia L.) have been used traditionally as food and for medicinal purposes by South Pacific populations since over two thousand years. Recently noni fruit juice became very popular as health beverage worldwide. Manufacturers and distributors of noni juice often praise the high content of minerals and trace elements in conjunction with the geological situation of the origin of the raw noni material. We therefore performed an investigation about the metal concentration of noni fruit, leaf and soil samples from 42 different locations in French Polynesia, and of 16 commercial noni juices. Median concentrations of metals in noni fruit, leaf and fruit juice appeared in a normal range compared to other fruits, however, the variance between different locations was considerable. Noni fruits from lime soil were poorer compared to volcanic soil in most metals. Self-prepared noni juices did generally not serve for more then 10% of the daily requirement of trace elements and minerals per 100 ml. The metal concentration in noni fruit puree was higher compared to clear juice and reached 10% and 34% of the daily requirement in 100 ml for manganese and chromium respectively. The concentrations of toxic metals (As, Cd, Pb) were below 2% of the maximum permitted levels (MPL) in all of these juices. For one of the commercial noni juices the MPL for lead was exceeded (170%) and some others were close to it. Most metals showed a good correlation regarding the concentration in noni fruit versus leaf, but not for soil versus fruit or juice. The concentration of magnesium, manganese, zinc and germanium in the commercial juices was highly correlated to the potassium concentration, indicating that these elements are useful to detect a dilution of noni juices.