The extracts were analyzed using silica gel thin layer chromatographic plates 20 x 20 cm from Sigma and submitted a quantitative analysis of the secondary metabolites, consisted in the spraying of distinct chromatographic plaques containing the extracts as reagent Lieberman-Burchard, Fe[Cl.sub.3], Al[Cl.sub.3], the foam test and Dragendorff reagent
, to evaluate the presence of steroids, flavonoids, saponins, tannins and alkaloids.
Whole fresh leaves at different developing stages were separately put on a glass slide and dyed with a few drops of improving Dragendorff reagent for 2-4 minutes.
The leaf sections were covered with a few drops of improving Dragendorff reagent for 20-30 seconds.
Both capitate trichomes (Figure 2(a)) and peltate trichomes (Figure 2(b)) were orange after dyed with Dragendorff reagent. The epidermis of leaves was colourless.
S3, Dragendorff reagent, prepared as in Clarke 
S6, iodinated Dragendorff reagent: 5 g of potassium iodide, 2 g of iodine, and 0.2 g of bismuth subnitrate (Sigma B9009) mixed in water, followed by 0.5 mL each of glacial acetic acid and concentrated HCI, and brought to 250 mL with deionized water