Phytochemical Characterization of Hibiscus tiliaceus L. Leaves and Evaluation of Their Antisickling, Antioxidant, and Anti-Inflammatory Activities.

Sickle cell disease (SCD) is a neglected tropical disease (NTD) associated with severe health consequences, including death. Hibiscus tiliaceus L., from the Malvaceae family, is used traditionally in Kisangani, Democratic Republic of the Congo (DRC), to alleviate symptoms of SCD. However, the specific phytochemicals responsible for the observed therapeutic effects remain unclear. This study aims to characterize the aqueous leaf extract of H. tiliaceus and assess its biological activity against sickle cell disease, including its antisickling, antioxidant, and anti-inflammatory effects. Using techniques such as TLC, HPLC-UV/DAD, LC-MS, and NMR, we identified kaempferol 3-O-rutinoside and rutin in the aqueous extract of H. tiliaceus leaves. Rutin exhibited potent antioxidant and anti-inflammatory activities, with IC50 values of 5 µg/mL and 2.5 µg/mL, respectively. Conversely, kaempferol 3-O-rutinoside demonstrated superior antisickling activity, normalizing sickled red blood cells with an IC50 < 12.5 µg/mL. Due to the pathophysiology of SCD, which involves the polymerization of red blood cells, which induces oxidative stress and an inflammatory response, this study suggests the importance of H. tiliaceus for the management of SCD. Additionally, the combined effect of molecules in H. tiliaceus will help in normalizing erythrocytes, inhibiting free radicals generated by early hemolysis, thus contributing to inflammatory processes reduction. This finding provides evidence and validates the traditional use of H. tiliaceus aqueous extract for the management of SCD.