Study on exosite inhibitor of cathepsin K from Herba Ecliptae fractions / 药学学报

Cathepsin K (CTSK) is considered a critical pharmaceutical target in the treatment of osteoporosis. CTSK exerts proteolytic activities against regulatory proteins besides its collagenase function, which may account for some of the adverse reactions when blocked by active site-directed inhibitors. Exosite inhibitors that can discriminate between the therapeutic collagenase and other biological activities of CTSK specifically inhibit the collagenase activity of CTSK without interfering with the other proteolytic activities of the protease. Active recombinant CTSK was expressed in Pichia pastoris, and purified by n-butyl sepharose and SP sepharose column chromatography. Herba Ecliptae is a common traditional Chinese medicine in the treatment of bone diseases. Collagenase assay and benzyloxycarbonyl-Phe-Arg-7-amido-4-methylcoumarin (Z-FR-MCA) substrate assay based on CTSK are applied to verify the exosite inhibitors. n-Butanol extract of Herba Ecliptae are the most active fraction and eclalbasaponin IX isolated from n-butanol fraction is the potential exosite inhibitor of CTSK.

Inhibition of LDL-oxidation and antioxidant properties related to polyphenol content of hydrophilic fractions from seaweed Halimeda Incrassata (Ellis) Lamouroux

LDL oxidation and oxidative stress are closely related to atherosclerosis. Therefore, natural antioxidants have been studied as promising candidates. In the present study, the LDL oxidation inhibition activity of bioactive compounds from Halimeda incrassata seaweed. associated to antioxidant capacity, was evaluated in vitro. Experimental work was conducted with lyophilized aqueous extract and phenolic-rich fractions of the seaweed and their effect on LDL oxidation was evaluated using heparin-precipitated LDL (hep-LDL) with exposure to Cu2+ ions and AAPH as the free radical generator. H. incrassata had a protective effect for hep-LDL in both systems and the presence of phenolic compounds contributed to the activity where phenolic-rich fractions showed significant capacity for inhibition of oxidation mediated by Cu2+ ions. The observed effect could be related to the antioxidant potential of polar fractions evidenced by reducing activity and DPPH• radical scavenging. The results obtained in vitro further support the antioxidant and LDL oxidation inhibition properties of H. incrassata and further knowledge toward future phytotherapeutic application of the seaweed.

A oxidação da LDL e o estresse oxidativo estão intimamente relacionados com a aterosclerose. Por isso, os antioxidantes naturais têm sido estudados como candidatos promissores. No presente trabalho foi avaliada in vitro a capacidade de inibição da oxidação da LDL pelos compostos bioativos da alga Halimeda incrassata em associação à capacidade antioxidante. O trabalho experimental foi conduzido com extratos polares (extrato aquoso liofilizado e frações ricas em fenólicos) e seu efeito na oxidação da LDL foi avaliado usando LDL precipitada com heparina (hep-LDL), oxidada com íons de Cu2+ e AAPH, como geradores de radicais livres. A H. incrassata apresentou efeito protetor para hep-LDL em ambos sistemas e a presença de compostos fenólicos contribuiu para a atividade em que as frações ricas em fenólicos demonstram capacidade significativa em inibir a oxidação mediada pelos íons de Cu2+. O efeito observado deve estar relacionado com o potencial antioxidante das frações polares medido pela atividade redutora e varredura do radical DPPH. Os resultados obtidos demonstram as propriedades antioxidantes e de inibição da oxidação da LDL da H. incrassata e podem contribuir para as evidências de futuras aplicações fitoterapêuticas desta alga.