Agathisflavone is a natural biflavone with restricted occurrence in plants. This biflavone presents several biological activities and can be important to developing new drugs. Obtaining such a molecule on a large scale for in vivo tests is a challenge. To date, there are no reports regarding its synthesis; thus, it is important to improve and develop methods for the purification of this bioactive compound from natural sources. Previous studies indicated that the leaves of Poincianella pyramidalis (Leguminosae) had agathisflavone predominantly. However, obtaining this compound requires some steps of chromatographic procedures and extraction with organic solvents. This paper compares four procedures for the purification of agathisflavone from its leaves, two by traditional chromatographic techniques and by complexation with inorganic bases. The purification in the automatic flash chromatography in two steps provides a high-yield extraction; the two procedures using alkaline extraction and the traditional method reduced to three steps provided the compound with similar yields. The biflavone was identified by TLC, and HPLC analysis showed that it was isolated with > 99% of purity. Thus, the applied methodologies provided the purification of this compound employing less volume of solvents, the number of chromatographic column procedures, and time-consuming, with increased yields.

This work describes the isolation of pure bergenin from Peltophorum dubium roots with good yields and its further derivatization through Williamson synthesis. The alkyl derivatives of the bergenin were identified by nuclear magnetic resonance and mass spectrometry data analysis. Among them, three derivatives were reported for the first time herein, 8,10-dihexyl-bergenin, 8,10-didecyl-bergenin, and 8,10-ditetradecyl-bergenin, along with three previously reported ones (8,10-dimethylbergenin, 8-methylbergenin, 8,10-dioctyl-bergenin). Most derivatives of the bergenin displayed moderate cytotoxicity against Artemia salina, except the 8,10-dihexyl-bergenin (lethal concentration doses for 50% (LC50) = 70.55 µg mL-1). The antimicrobial assay showed that all derivatives selectively inhibited the Gram-positive bacteria Staphylococcus aureus, and two of them (8,10-dihexyl-bergenin and 8,10-didecyl-bergenin) had promising activities (minimum inhibitory concentration (MIC) = 5.1-6.2 µmol L-1). In addition, bergenin displayed interesting inhibition on acetylcholinesterase (half maximal inhibitory concentration (IC50) = 141.19 ± 0.41 µmol L-1), while its semi-synthetic derivatives displayed modest activity. Our results revealed that the antibacterial activity of bergenin could be greatly improved through its structural modification.