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.

Our study explored the scientific rationale behind the traditional use of medicinal plants as a foundation for evidence-based strategies for the management of sickle cell disease (SCD) in developing countries. Firstly, we conducted a survey among people living at Kisangani city in DR Congo to identify the plants used alone or in combination for the SCD management considering the following criteria: used parts, preparation methods, administration routes and common combinations with other substances. This step allowed to select the most used plants which were harvested from two different soil types and prepared according to local practices. Secondly, different preparations were tested at laboratory focusing on the antioxidant and anti-inflammatory biological activities which are mainly observed with people suffering from SCD. Out of 384 surveyed people, 201 reported the use of 45 medicinal plants whereas the additives comprised sugar, caramel, ash and lemon juice. Alchornea cordifolia Müll. Arg and Hibiscus tiliaceus L. were selected for laboratory analyses. Their leaves were collected from both dry and marshy soils and prepared following local methods with additive. A. cordifolia showed significantly higher antioxidant (p = 0.001) and anti-inflammatory activity (p = 0.01) than H. tiliaceus. Soil type influenced activity in H. tiliaceus, favoring marshy soil. However, sugar and caramel significantly reduced bioactivity, ash and lemon juice enhanced antioxidant effects without significantly altering anti-inflammatory properties.

In traditional medicine, laboratory tests are essential tools used to evaluate practices in healthcare that use natural products, particularly when there are few established treatments such as in the case of chronic diseases like sickle cell disease (SCD). SCD is a genetic hemoglobin disorder associated with hemolysis, oxidative stress, inflammation, and vaso-occlusive complications. This study aims to document medicinal plants used in the management of SCD and the traditional practices associated with their use, in order to assess their added value in relation to biological activities relevant to SCD. First, this study carried out an ethnobotanical survey at Kisangani, with 384 participants. A total of 201 respondents, 58% of whom were women, identified 45 medicinal plant species from 30 families. They reported the use of sugar, caramel, ash, and lemon juice as additives in traditional remedies. Based on several criteria, Alchornea cordifolia Müll. Arg. and Hibiscus tiliaceus L. were selected for laboratory evaluation. Their leaves were collected from arid and marshy soils and prepared according to the respondents’ descriptions for antioxidant and anti-inflammatory assessments. A. cordifolia showed significantly higher activities than H. tiliaceus regarding antioxidant (p = 0.001) and anti-inflammatory (p = 0.01) properties. Soil type was observed to influence the bioactivity of H. tiliaceus, with better performance in marshy soil samples. Sugar and caramel were found to reduce antioxidant activity, whereas ash and lemon juice preserved it without markedly altering anti-inflammatory effects. These findings are promising for supporting local knowledge about these two plant species.