Abstract
The purification of the hexanic extract from the leaves of a native variety of mahogany collected in Santarem (Para, Brazil) afforded eight new phragmalin limonoids along with eight known compounds. This variety, according to field observations, should be considered resistant against the specialist insect Hypsipyla grandella, that attacks the terminal shoots only of juvenile mahogany and not of matured ones. After observing that four phragmalin limonoids were present just in mature leaves, we carried out two bioassays, one of them using a fraction from hexanic extract of mature leaves and another using a mix of four limonoids. The results of the bioassay using the isolated limonoids showed a direct effect on the larvae of H. grandella, suggesting that these limonoids act as inhibitors of larvae growth. This should be the reason why larvae choose the young leaves for their development.
Highlights
Brazilian mahogany, known as big-leaf mahogany, has been extensively studied, indicating a wide variety of biological activities such as antimicrobial,1 antiinflammatory,2,3 antioxidant,4-6 hypolipidemic7-9 and antifeedant.10,11Despite all these biological activities, the high commercial value of sawn mahogany timber continues to deliver the greatest demand for this species
At Tramontina Farm, that Santarém varieties were less attacked by H. grandella larvae, led to the hypothesis that this was a case of resistance
Based on the hypothesis that the Santarém variety might have a resistance to the larvae of H. grandella, we investigated its chemical composition, using LC‐HR‐electrospray ionization (ESI)‐ToF‐MS through fingerprint analysis, focusing specially on limonoids content, since they are the taxonomic markers of Meliaceae
Summary
Known as big-leaf mahogany, has been extensively studied, indicating a wide variety of biological activities such as antimicrobial,1 antiinflammatory,2,3 antioxidant,4-6 hypolipidemic7-9 and antifeedant.10,11Despite all these biological activities, the high commercial value of sawn mahogany timber continues to deliver the greatest demand for this species. Limonoid 2 exhibited similar NMR spectra (Tables S1 and S2, SI section) to those of swietephragmin I (16; C36H42O13), which has previously been isolated from the leaves of S. macrophylla collected in Malaysia.27 HR‐ESI‐ToF‐MS indicated the molecular formula to be C38H44O15 for compound 2, requiring the presence of two additional oxygens and carbons in comparison with 16.
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