Investigation of thermal behavior of Heliotropium indicum L. lyophilized extract by TG and DSC

Thermogravimetric (TG) techniques and differential scanning calorimetry (DSC) used for the study of pre-formulation or drug–adjuvant compatibility have been gaining importance in Brazil. These techniques are being used for the verification of possible interactions between drugs and adjuvants. Aiming at studying the behavior of a plant extract and its mixture with adjuvants, using these thermoanalytical techniques the plant species Heliotropium indicum L. was used. This plant which is originally from India and has been well acclimatized in Brazil has healing and anti-inflammatory properties. The methodology for obtaining the extract followed the Brazilian Pharmacopoeia methodology. And the incorporation of the extract with adjuvants was through binary mixtures (1:1 w/w). The TG and DSC curves were obtained under nitrogen atmosphere (25 mL min^?1) at a heating rate of 5 °C min^?1; TG tests were analyzed within a temperature range from 25 to 600 °C and DSC from 25 to 300 °C. The TG curves show good thermal stability of the extract and its mixtures with adjuvants up to 150 °C, except the propylene glycol (PLG). The DSC curves revealed an incompatibility of the extract with methylparaben and PLG mixture.