|Other Abstract||Nostoc, as cyanobacteria in gereral, are widely distributed on earth. Many secondary metabolites with new structures have been isolated from these organisms. Due to their value of antiviral and antitumor activity, etc., the development and utilization of these bioactive compounds have gained much interest. This research screened secondary metabolites with tyrosinase inhibitory activity and trypsin inhibitory activity, etc. from 10 strains of Nostoc. In addition, the effects of different growth conditions (nutritional factors and environmental factor) on the production of bioactive compounds are investigated as well for the future culture, further development and utilization of these bioactive compounds.
Through the screening of tyrosinase inhibitor, trypsin inhibitor and other bioactivity, it was found that 6 strains of Nostoc exhibit tyrosinase inhibitory activity, which are N. sp. FACHB95, N. sp. FACHB106, N. punctiforme FACHB252, N. calcicola FACHB389, N. parmelioides FACHB392, and N. sp. FACHB892, with IC50 of 43.21, 43.95, 33.32, 29.67, 41.32 and 23.92 µg/mL respectively, and 5 strains of Nostoc own inhibitory activity on trypsin, which are N. paludosum FACHB89，N. sp. FACHB106，N. sp. FACHB139，N. calcicola FACHB389，and N. parmelioides FACHB392. In general, the inhibitory ability on trypsin are weaker than that of tyrosinase. Meanwhile, the extracts from 7 strains have positive or negative effects on the genesis of superoxide anion free radical, which are N. paludosum FACHB89, N. sp. FACHB95, N. linckia FACHB103, N. punctiforme FACHB252, N. calcicola FACHB389, N. parmelioides FACHB392 and N. sp. FACHB892。
By comparing the autotrophic and mixotrophic conditions, it could be concluded that BG-11 medium with 5 mM glucose help to increase the inhibitory activity on tyrosinase from the extracts of N. calcicola FACHB389. And at the concentration of 33.3 µg/mL, the inhibitory rate of extract of N. calcicola FACHB389 on tyrosinase has a positive correlation with the content of TOC. While investigating the effects of phosphate concentration and light intensity on the production of tyrosinase inhibitor from N. calcicola FACHB389 by central composite design, the results suggest that phosphate concentration and light intensity have no interaction effects on the production of tyrosinase inhibitor, the content of tyrosinase inhibitor change with culture time, high phosphate concentration (70 mg/mL) and optimum light intensity (30 µmol• m-2• s-1) help the accumulation of tyosinase inhibitor in N. calcicola FACHB389 during stationary phase.|