In order to obtain bioactive secondary metabolites, we investigated the chemical constituents of Hypoestes forskaolii Vahl. Roem. & Schult. (Acanthaceae) roots. H. forskaolii is a perennial herb widely distributed in many African countries as well as in the Arabian peninsula [1]. The whole plant is popularly used as natural insecticide, moreover fresh leaves are used by locals to accelerate the healing process. Various biological properties have been attributed to the plant, including antiplasmodial, antifungal, antiparasitic and cytotoxic properties [2]. Several Hypoestes species have been chemically investigated before establishing that diterpenes belonging to the class of fusicoccane, isopimarane, and labdane are the main skeleton synthesized by these species [3].
Fusicoccanes characterized by a complex 5-8-5 dicyclopenta-cyclooctane nucleus, are powerful phytotoxins in Hypoestes and different fungi species [3].
Eleven new fusicoccane diterpenes were isolated from the dichloromethane extract of H. forskaolii roots by CC, MPLC and RP-HPLC chromatography, together with two known lignans. All structures were elucidated on the basis of NMR and HR-MS spectroscopic methods. Additionally, the affinity of isolates towards Hsp90, one of the most promising targets for anti-cancer therapy, was tested by surface plasmon resonance. Results demonstrated that 17-hydroxy-hypoestenone efficiently interacted with the protein (KD 0.32 mM). The study of the activity of 17-hydroxy-hypoestenone by means of a panel of biochemical and cellular approaches was achieved. 17-hydroxy-hypoestenone showed an antiproliferative activity with an EC50 of 26 µM on the HeLa cell line by inducing a G2/M cell cycle block through the down-regulation of pCdc2 protein levels.
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[2] Pettit G R, Goswami A, Cragg GM, Schmidt M, and Zou JC. J Nat Prod 1984, 47: 913-16
[3] de Boer AH, de Vries-van Leeuwen IJ. Trends Plant Sci 2012; 17: 360-368.