Derivatization of cassane diterpenoids from Caesalpinia pulcherrima (L.) Sw. and evaluation of their cytotoxic and leishmanicidal activities

- An easy method for the oxidation of furanocassane diterpenoids.
- Acid-catalysed stereoselective hydroxylation of an electrophilic carbon.
- The method could open new avenue for derivatisation of cassanediterpenoids.

Oxidation of the cassane diterpenoids 6β-cinnamoyl-7α-hydroxyvouacapen-5α-ol (1) and pulcherrimin A (2), which were isolated from the roots of Caesalpinia pulcherrima, yielded four new derivatives 3-6. The structures of the new compounds were confirmed on the basis of 1D and 2D NMR spectroscopy as well as mass spectrometry. The derivatives were tested for their cytotoxic activity against three cancer cell lines (MCF-7, HeLa, and PC-3) and their leishmanicidal activity against Leishmania major. Compound 4 showed cytotoxic activity against all cell lines (IC50 = 5.67 ± 0.07, 3.16 ± 0.16, and 7.90 ± 1.60 μM against MCF-7, HeLa, and PC-3, respectively), and was 2-3 times more active than the parent compound 1. Compound 6 showed significant leishmanicidal activity (IC50 = 9.18 ± 0.48 μg/mL), whereas the parent compound 2 was inactive.