An isoindolone derivative, Fungi fibrinolytic compound (R)‐2,5‐bis((2R,3R)‐2‐((E)‐4,8‐dimethylnona‐3,7‐dien‐1‐yl)‐3,5‐dihydroxy‐2‐methyl‐7‐oxo‐3,4,7,9‐tetrahydropyrano[2,3‐e]isoindol‐8(2H)‐yl)pentanoic acid (FGFC1, Fungi fibrinolytic compound 1), was isolated from a rare marine microorganism strain Stachybotrys longispora FG216. The structure of FGFC1 was elucidated by 1H NMR, 13C NMR, IR, and MS data; moreover, it was also evaluated for fibrinolytic activity in vitro and in vivo. The results showed that 0.1–0.4 mmol/L of FGFC1 could stimulate generation of plasmin activity (increased by 2.05–11.44 folds) by measuring Glu‐plasminogen and Lys‐plasminogen activation in vitro. The experiment of fluorescein isothiocyanate (FITC)‐fibrinogen degradation indicated that the effect of FGFC1 on fibrinolytic activity was mediated by plasminogen and scuPA. In addition, FGFC1 (10 mg/kg) could dissolve most of pulmonary thrombus of Wistar rat in vivo. It is possible that FGFC1 is a potential thrombolytic agent in the future.

A low molecular weight type-II collagenous polypeptide (CIIp) from whale shark (WS) cartilage was prepared by thermolysin digestion; and examined for their physico-functional and antioxidant properties. The purified collagen was composed of an identical (α 1 ) 3 chains and was characterized as type-II. After hydrolysis with thermolysin, the α-chain of the WS collagen was degraded into smaller peptides with molecular weight ranging from 70 to 20KDa. CIIp was successfully separated from the hydrolysates with molecular weight of approximately 37 kDa. Amino acid analysis of CII, and CIIp indicated imino acid contents of 155 and 121 amino acid residues per 1000 residues, respectively. Differing Fourier transform infrared (FTIR) spectra of CII and CIIp were observed, which suggested that the hydrolysis process by thermolysin affected the secondary structure and molecular order of collagen, particularly the triple-helical structure. The denaturation temperature of CII (34°C) was higher than that of CIIp. Low content of glycoprotein was observed in CII than CIIp due to removal of some polypeptides by thermolysin digestion. The antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl radicals and the reducing power of CIIp was greater than that of CII. The results proposed that the purified CIIp from WS cartilage with excellent antioxidant activities could be the suitable biomaterial for therapeutic applications.

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A marine fibrinolytic compound FGFC1 enhancing fibrinolysis was obtained involving enzymatic kinetic parameters of a reciprocal activation system with a single chain urokinase type plasminogen activator and plasminogen. FGFC1, a kind of bisindole alkaloid from a metabolite of the rare marine fungi Starchbotrys longispora FG216, modulated enzymatic kinetic parameters including the fibrinolytic reaction rate and fibrin degradation characteristics. The enzymatic kinetics of fibrinolysis was described based on the enzymatic reaction of a chromogenic-substrate associated with p-nitroaniline (p-NA). While the single chain urokinase-type plasminogen activator (pro-uPA) activated plasminogen, kcat and kcat/Km increased significantly with an increase of FGFC1 concentration. Moreover, kcat and kcat/Km exhibited 26.5-fold and 22.8-fold enhanced activity at the concentration of 40 μg·mL −1 of FGFC1, respectively. The results suggested that FGFC1 significantly improved the maximum catalytic efficiency and the total catalytic activity of fibrinolysis base on the reciprocal activation of pro-uPA and plasminogen. Km increased with increasing FGFC1 concentration, which indicated that FGFC1 slightly decreased the affinity activity of the pro-uPA and plasminogen versus the enzyme substrate. The marine bisindole alkaloid FGFC1 enhanced fibrinolysis, which was taken on enzymatic kinetic characteristics.