Abstract
Despite the extensive studies on latex, some fundamental questions on their chemical
specialization and the factors influencing this specialization have yet to be investigated.
To address this issue, latexes and their bearing tissues from diverse species were
profiled by 1HNMR and GC-MS. Additionally, the antiherbivory activity of these materials was tested
against thrips (Frankliniella occidentalis Pergande, 1895). The multivariate data analysis showed a clear separation between
latexes and leaves from the same species. Conversely, the chemical profiles of latexes
from different species were highly similar, that is, they displayed much less metabolic
species-specificity. These shared chemical profiles of latexes were reflected in their
overall higher mortality index (80.4% ± 7.5) against thrips compared with their bearing
tissues (55.5% ± 14.9). The metabolites correlated to the antiherbivory activity of
latexes were triterpenoids and steroids.
However, the activity could not be attributed to any single terpenoid. This discrepancy
and the reduction of the latex activity after fractionation suggested a complementary
effect of the compounds when in a mixture as represented by the latex. Additionally,
aqueous fractions of several latexes were found to possess simple spectra, even with
only 1 metabolite. These metabolites were determined to be organic acids that might
be involved in the modulation of the rate of latex coagulation, potentially increasing
the sealing and trapping effects of the latex.
Key words
Apocynaceae - Euphorbiaceae - Moraceae - Clusiaceae - triterpenes - organic acids
- latex
