Quantitative seasonal variation of the falcarinol-type polyacetylene (3S)-16,17-didehydrofalcarinol and its spatial tissue distribution in Tridax procumbens

Introduction (3S)-16,17-Didehydrofalcarinol (1) has been isolated from Tridax procumbens and has proved to have notorious bioactivity against Leishmania mexicana. In this study, hexane fractions obtained from the methanol extract of each plant part (roots, stems, leaves, flowers, and fruits) of T. procumbens collected monthly during a year were analysed in order to determine the quantity of 1 associated with biotic variables. Objective The aim of this study was to find the season of the year in which the bioactive metabolite 1 is at the highest concentration and to correlate it with temperature, length of day light, and rainfall. Methods Hexane fractions were obtained by liquid-liquid extraction and an accurate quantitation of 1 was performed using gas chromatography with a flame ionisation detector (GC-FID) employing pelargonic acid vanillyl amide (2) as internal standard. Partial validation was based on linearity and precision. Results Our results indicated that the total content of 1 has significant variation (P <= 0.05) during the different collecting months. The total content of the metabolite reached its highest level in the roots of the plant during June in the rainfall season (0.0358 +/- 0.001 mg/g), and its lowest values in February and March during the drought season (0.0015 +/- 0.000 and 0.0008 +/- 0.000 mg/g, respectively). Conclusion Our study provided evidence that the content of 1 in roots is strongly influenced by the variables of the harvesting season, also indicating that the biosynthesis of the active metabolite is enhanced during the warm and rainy months.