Supercritical extraction of coumarin from guaco (Mikania laevigata and Mikania glomerata) for pharmaceutical applications

Guaco has several applications in the chemical and pharmaceutical industries. This plant is a source of coumarin, a diterpene compound with expectorants properties. In Brazil, guaco extracts are used as medicinal products authorized by the National Health Surveillance Agency (ANVISA). Studies proved that guaco extracts are also effective against cancer, ulcers and infectious diseases. Supercritical extractions have been widely used to obtain highly pure natural extracts that do not contain organic solvents and have not lost their thermosensitive compounds and therefore are suitable for pharmaceutical applications. In this study, coumarin was obtained from guaco leaves extracts by supercritical extraction under different experimental conditions according to a central composite rotational design (CCRD) with two independent variables, temperature (T) and pressure (P). Lower values of T were used to maintain the stability of thermosensitive compounds and because coumarin is highly soluble in supercritical CO2 even at low T. The responses surface analyzes (RSA) acquired by fitting of linear and quadratic models to experimental extraction yields and coumarin concentrations showed similar conditions for improving yields from both plant species. Although the extract yield values were similar for both plant species, coumarin concentrations were higher in Mikania laevigata than Mikania glomerata. The greater extract yield of 4.20% coumarin, related to the higher coumarin concentration (0.43 g × 100 g−1 in guaco leaves), was obtained under extraction conditions of P above 175 bar and T above 45 °C.