Impact of temperature on the biosynthesis of cytotoxically active carbamidocyclophanes A–E in Nostoc sp. CAVN10

The effects of different temperatures on biomass production and carbamidocyclophane biosynthesis of the cyanobacterium Nostoc sp. CAVN10 were investigated under batch cultivation conditions over 30 days. Cyanobacterial growth correlated with increasing temperatures from 18 to 33 °C but revealed different specific growth rates within the cultivation period. The accumulation of carbamidocyclophanes A–E was investigated at different growth stages, and their levels were quantified by HPLC-UV analysis. The highest dry weight content of 1.5 % for carbamidocyclophane A, 1.0 % for carbamidocyclophane B, and 1.1 % for carbamidocyclophane C was found around the 15th day at 28 °C. At 33 °C, however, yields of these compounds decreased significantly, but the content of carbamidocyclophanes D and E continuously increased to 0.4 % on the 25th day. In general, carbamidocyclophanes showed cytotoxic activity against LN18 glioblastoma cells and 5637 human urinary bladder carcinoma cells with half maximal inhibitory concentration (IC 50 ) values of 2.1–3.1 μM and 0.8–2.1 μM. Only carbamidocyclophane D exhibited a less potent cytotoxicity against 5637 cells with an IC 50 value of 10.1 μM.