Risk of Aluminum Exposure from Noni (Morinda citrifolia L.) Leaf Products1

Accumulation of soil aluminum in plant tissues can increase aluminum exposure during use of botanical products for food or medicines. We determined the potential for excessive exposure to aluminum in leaves of Morinda citrifolia (Rubiaceae) trees growing in eight contrasting soils in four Western Pacific islands. Mean aluminum content of green leaves ranged from 47–536 μg⋅g-1 tissue dry weight among the eight sites. Mean aluminum content of yellow, senescing noni leaves ranged from 96–988 μg⋅g-1 tissue dry weight. The trees growing in acid soils exhibited greatly elevated aluminum concentration when compared with trees growing in alkaline soils, and leaves from one replication in acid soils exhibited 1659 μg·g-1 aluminum. Results indicate avoidance of old leaves and trees growing in acid soils would greatly reduce aluminum exposure during ingestion of M. citrifolia leaf products.