Evaluation of the inhibitory potential of five squaric acid derivatives against pancreatic lipase

Strong inhibitory activities and action modes of lipopeptides on lipase

Lipopeptides have been reported to exhibit anti-obesity effects. In this study, we obtained a Bacillus velezensis strain FJAT-52631 that could coproduce iturins, fengycins, and surfactins. Results showed that the FJAT-52631 crude lipopeptide, purified fengycin, iturin, and surfactin standards exhibited strong inhibition activities against lipase with dose-dependence manners (half maximal inhibitory concentration (IC₅₀) = 0.011, 0.005, 0.056, and 0.005 mg/mL, respectively). Moreover, fengycin and surfactin had the comparable activities with orlistat, but iturin not. It was revealed that the inhibition mechanism and type of the lipopeptides were reversible and competitive. The quenching mechanism of lipase was static and only one binding site between lipase and lipopoeptide was inferred from the fluorescence analysis. The docking analysis displayed that fengycin and surfactin could directly interact with the active amino acid residues (Ser or Asp) of lipase, but not with iturin. Our work suggests that the B. velezensis lipopeptides would have great potential to act as lipase inhibitors.

Inhibitory kinetics and bioactivities of Nuciferine and Methyl Ganoderate on Mucor miehei lipase and 3T3-L1 preadipocytes

In this study, inhibitory kinetics of Nuciferine and Methyl Ganoderate extrated from Lotus Leaves and Ganoderma lucidum on Mucor miehei Lipase were studied first. The molecular structure of Nuciferine and Methyl Ganoderate were determined. The inhibitory effects of two extracts on lipase were reversible, with the IC₅₀ values of 0.194 and 0.332 mg/mL, respectively. The inhibition kinetic analysis by Lineweaver-Burk plots showed that they were a mixed-type inhibitor of lipase, with inhibition constants K_I of 0.16 and 0.29 mg/mL, and K_IS of 0.36 and 0.49 mg/mL, respectively. Results of spectral analysis showed that the UV absorption and the molecule fluorescence spectrum of the lipase hydrolyzate were significantly decreased after the inhibitor was added. The molecular docking further suggested that the interaction site between the active substance and inhibitor was located in an α-helix and a β-sheet of the lipase, and the lipase active site was interfered by the inhibitor near the cap structure. In addition, the proliferation and differentiation of 3 T3-L1 preadipocytes were inhibited by two extracts. Total triglycerides and cholesterol were significantly reduced in the cells. The results confirmed that Nuciferine and Methyl Ganoderate can be used as potential obesity treatment drugs.

Glycosyl squaramides, a new class of supramolecular gelators

Glycosyl squaramides were synthesised and evaluated as low molecular weight gelators. Amphiphilic glycosyl squaramides 5 and 6, with a C-16 aliphatic chain, formed thermoreversible gels in polar organic solvents and 1 : 1 ethanol/water mixtures with high efficiency. Rheological analysis showed these gels achieve their structural stability 120 h after gelation and were robust, making them particularly suitable for biomedical applications. The interactions between solvent and gelator strongly influence SAFiN (Self-Assembled Fibrillar Network) formation, critical gelation concentration (CGC) and subsequent gel structure, as evidenced by SEM imaging of xerogels. Spectroscopic studies indicate that H-bonding is involved in the self-assembly of the glycosyl squaramides in organic solvents, while hydrophobic interactions are the major driving force for gel formation in the presence of water. The compounds described herein are the first reported examples of carbohydrate-squaramide conjugates capable of forming supramolecular gels.