Studies on toad venom (3): effect of metals on the quality of toad venom torrefied on a metal plate

To study the quality of toad venom dried on different metal plates by heating at 105 degrees C, each 20 g sample of fresh toad venom collected in Hei-Long-Jiang Province, China, was dried on (1) brass, (2) copper, (3) glass, (4) acrylic resins, (5) aluminum and (6) stainless-steel, respectively. Twelve bufadienolides, including bufalin and bufotalin, in each sample were then quantitatively analyzed by HPLC. The total levels of bufadienolides in 1000.0 mg of the dried samples were (1) > (2) > (3) > (4) > (5) > (6), varying from 303.44 mg to 420.72 mg. Besides, the color of dried venom became darker in the order of (2), (4), (6), (3), (1) and (5). Though (1) was not in good color, it was superior to the others in chemical quality. These results suggest that it is possible to dry toad venom in short period by heating it at a high temperature on a tray made of brass. This will be a better method for making high quality toad venom than the traditional method. Moreover, the removal of impurities in the fresh venom by the process of filtration through silk succeeded in raising the bufadienolides content significantly.