Identification of Bichalcones as Sirtuin Inhibitors by Virtual Screening and In Vitro Testing.

Sirtuins are nicotinamide adenine dinucleotide (NAD⁺)-dependent class III histone deacetylases, which have been linked to the pathogenesis of numerous diseases, including HIV, metabolic disorders, neurodegeneration and cancer. Docking of the virtual pan-African natural products library (p-ANAPL), followed by in vitro testing, resulted in the identification of two inhibitors of sirtuin 1, 2 and 3 (sirt1-3). Two bichalcones, known as rhuschalcone IV (8) and an analogue of rhuschalcone I (9), previously isolated from the medicinal plant Rhus pyroides, were shown to be active in the in vitro assay. The rhuschalcone I analogue (9) showed the best activity against sirt1, with an IC50 value of 40.8 µM. Based on the docking experiments, suggestions for improving the biological activities of the newly identified hit compounds have been provided.

Total synthesis, antiprotozoal and cytotoxicity activities of rhuschalcone VI and analogs.

The total synthesis of a potent antiplasmodial natural bichalcone, rhuschalcone VI, is described starting from simple and available resorcinol and 4-hydroxybenzaldehyde. Key steps include the solvent-free Aldol syntheses of chalcones, and the successful application of the Suzuki-Miyaura coupling reaction in the synthesis of bichalcones. The present work constitutes a general method for the rapid syntheses of a number of bichalcones related to rhuschalcone VI. Some of the bichalcones showed moderate antiprotozoal activities against Bodo caudatus, a preliminary screening system for antitrypanosomal activities, most of them with little or no cytotoxicity.