Toward a More Sustainable Sample Preparation in Phytochemistry: Case Studies in Four Subclasses of Alkaloids

The fact that alkaloids are bases has been the most explored chemical feature of their extraction and purification procedures. The main drawback of these procedures is that they employ undesirable chemicals, with HCl and CH₂Cl₂ probably being the most commonly employed chemicals in their subsequent steps. This work tested the hypothesis that advantages in recovery efficiency support this common practice. Experiments were conducted in three laboratories, monitoring the alkaloids harmine (1), boldine (2), vincamine (3), and mescaline (4) extracted from Banisteriopsis caapi, Peumus boldus, Vinca minor, and Trichocereus macrogonus var. pachanoi, respectively. The research demonstrated that HCl could be replaced with citric acid (CA) without loss or even better extraction performance. The recommended EtOAc could completely replace CH₂Cl₂ in three out of four study cases and partially in the fourth case without harming the extraction efficiency. In addition, the alternative solvents tert-amyl methyl ether (TAME) and n-butyl acetate (BuOAc) could enhance the extraction of alkaloids. These results might incentivize natural products laboratories to consider sustainability more routinely, thus being closer to current practices in the pharmaceutical industry, which has been replacing solvents and processes with greener ones.