Replant problem in Casuarina equisetifolia L.: Isolation and identification of allelochemicals from its roots

To understand the replant problem in Casuarina equisetifolia L. plantations, we isolated and identified five chemicals [12, 13-dihydromicromeric acid (M-1),betulinic acid (M-2), 3-Ocaffeoyl lupeol (M-3), catechins (M-4) and epicatechin (M-5)] from its roots by electrospray ionization mass spectrometry and 1H and 13C nuclear magnetic resonance spectroscopy. Bioassays showed that the identified chemicals were inhibitory to C. equisetifolia i.e. its own germination and seedling growth. Among these, 12,13-dihydromicromeric acid was most harmful. These findings suggested that the identified chemicals may be the key allelochemicals in C. equisetifolia replant problem.