Extraction of antioxidant and ACE inhibitory peptides from Thai traditional fermented shrimp pastes.

Antioxidant and angiotensin converting enzyme (ACE) inhibitory peptides were extracted and isolated from two different types of Thai traditional fermented shrimp pastes, Kapi Ta Dam (Kp-B6) and Kapi Ta Deang (Kp-R6). Compounds with masses less than 500Da were found to be predominantly presented in both extracts. Following fractionation with sequential anion exchange chromatography and solid phase extraction (C18 matrix), three dipeptides were identified. Ser-Val and Ile-Phe were shown to exhibit ACE inhibitory activity with IC50 values of 60.68±1.06 and 70.03±1.45µM, respectively. Trp-Pro was shown to have high 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) radical scavenging activity (EC50 17.52±0.46µM). These results indicate that Thai traditional fermented shrimp pastes are potential sources of bioactive peptides possessing ACE inhibitory and antioxidant activities.

Liporetro-D-peptides - a novel class of highly selective thrombin inhibitors.

INTRODUCTION: Plasma serine protease thrombin plays a key role in coagulation, haemostasis and thromboembolic diseases. Direct thrombin inhibitors could be beneficial for future anticoagulant therapy. We have synthesized and studied liporetro-D-peptides - efficient thrombin inhibitors resistant to enzymatic degradation. MATERIALS AND METHODS: Compounds X-D-Arg-D-Phe-OMe, where X=residue of lauric or myristic acid or 9-fluorenylmethoxycarbonyl, have been synthesized by conventional peptide synthesis in solution and their comparative inhibitory analysis in relation to thrombin, factor X, plasmin and trypsin has been conducted. RESULTS: Modification of the synthetic liporetro-D-peptides with the myristic acid residue was the most successful one. This modification has dramatically increased the inhibition efficacy (Ki=0,17 µM) and selectivity toward the chosen target enzyme, thrombin, in comparison to factor X, plasmin and trypsin (more than 600, 900, and 5000-fold, respectively). CONCLUSIONS: Our findings establish an important role of the fatty moiety in the structure of peptide inhibitors with regards to their potency and selectivity toward thrombin.