Nuclear receptors (NRs) constitute a superfamily of ligand-activated transcription factors with a paramount role in ubiquitous physiological functions such as metabolism, growth, and reproduction. Owing to their physiological role and druggability, NRs are deemed attractive and valid targets for medicinal chemists. Pentacyclic triterpenes (PTs) represent one of the most important phytochemical classes present in higher plants, where oleanolic acid (OA) is the most studied PTs representative owing to its multitude of biological activities against cancer, inflammation, diabetes, and liver injury. PTs possess a lipophilic skeleton that imitates the NRs endogenous ligands. Herein, we report a literature overview on the modulation of metabolic NRs by OA and its semi-synthetic derivatives, highlighting their health benefits and potential therapeutic applications. Indeed, OA exhibited varying pharmacological effects on FXR, PPAR, LXR, RXR, PXR, and ROR in a tissue-specific manner. Owing to those NRs modulation, OA exhibited prominent hepatoprotective properties comparable to ursodeoxycholic acid (UDCA) in a bile duct ligation mice model and antiatherosclerosis effect as simvastatin in a model of New Zealand white (NZW) rabbits. It also demonstrated a great promise in alleviating non-alcoholic steatohepatitis (NASH) and liver fibrosis, attenuated alpha-naphthol isothiocyanate (ANIT)-induced cholestatic liver injury, and controlled blood glucose levels, making it a key player in the therapy of metabolic diseases. We also compiled OA semi-synthetic derivatives and explored their synthetic pathways and pharmacological effects on NRs, showcasing their structure-activity relationship (SAR). To the best of our knowledge, this is the first review article to highlight OA activity in terms of NRs modulation.

The limited supply of drinking water has aroused people's curiosity in recent decades. Adsorption is a popular method for removing hazardous substances from wastewater, especially heavy metals, as it is cheap, highly efficient and easy to use. In this work, a new sludge-based activated carbon adsorbent (SBAC1 / SBAC2) was developed to remove hazardous metals such as cadmium (Cd+2) and lead (Pb+2) from an aqueous solution. The chemical structure and surface morphology of the produced SBAC1 and SBAC2 were investigated using a range of analytical tools such as CHNS, BET, FT-IR, XRD, XRF, SEM, TEM, N2 adsorption/desorption isothermal and zeta potential. BET surface areas were examined and SBAC2 was found to have a larger BET surface area (498.386 m2/g) than SBAC1 (336.339 m2/g). SBAC2 had a lower VBJH (1.5026 cm3 g-1) than SBAC1 (1.59873 cm3 g-1), but a higher VT (0.3748 cm3 g-1) than SBAC1 (0.2688 cm3 g-1), while the average pore size was 10-100 nm for SBAC1 and 45-50 nm for SBAC2. The ideal conditions investigated for the removal of Pb+2 and Cd+2 were 10 mg SBAC1 / SBAC2, Pb+2 / Cd+2 at an starting concentration of 30 mg/L, a temperature of 40 and 50 °C, pH = 6, 8 and contact times of 10 and 15 minutes for Pb+2 and Cd+2, respectively. SBAC1 and SBAC2 eliminated approximately 99.99% of Cd+2 and Pb+2 out the water under all conditions tested. The results of the adsorption of Cd+2 and Pb+2 were in good agreement with the pseudo-second-order equation (R2 = 1.00). Under the experimental conditions, the Cd+2 and Pb+2 adsorption equilibrium data were effectively linked to the Langmuir and Freundlich equations for SBAC1 and SBAC2, respectively. Langmuir model calculated the adsorption capacities of SBAC1 and SBAC2 for Cd+2 (309.24 and 329.62 mg/g) and for Pb+2 (318.46 and 339.61 mg/g), respectively. The regeneration showed high recyclability for the fabricated SBAC1 and SBAC2 during five consecutive reuse cycles. As a result, the produced SBAC1 and SBAC2 are attractive adsorbent for the elimination of heavy metals from various environmental and industrial wastewater samples.