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Studies were conducted to determine the toxic compounds and potential pharmaceutical drugs in extracts of SPC 920- Geitlerinema unigranulatum. Lyophilized cells of G. unigranulatum were obtained from batch cultures and freeze-dried cells were extracted and submitted to HPLC analysis. The toxicity of lyophilized cells and chromatographic bands were determined using the mouse assay and the acetylcholinesterase inhibitory activity was recorded. Results showed that the G. unigranulatum crude extract exhibited a band at Rf 0.89, which was capable of inhibiting the enzyme AChE. In the mouse bioassay, the methanolic extract of lyophilized cells had a median lethal dose of 500 mg/kg BW. Mouse deaths occurred from 50 minutes to 19 h and the lungs were consolidated, but the livers had a normal appearance without typical signs of hepatotoxic intoxication.

The effects of the toxic methanolic extract (ME) of G. unigranulatum [G. amphibium] (SPC 920) on the microcirculation and muscle fibres of mice were studied using intravital microscopy. For topical administration, ME at 20, 40 or 120 µg diluted in 20 µlitres of sterile saline solution was applied to the cremaster muscle of the mice. For intraperitoneal administration, the doses used were 6, 125, 250, 500 and 1000 mg/kg body weight (BW). Analysis was conducted at 30 and 120 minutes after inoculation. The topical application of ME at 20 and 40 µg did not cause changes in the microcirculatory system. ME at 120 µg caused venular stasis immediately after its application, but this effect was only temporary. ME injection at 1000 mg/kg BW caused death in the animals at times ranging from 50 minutes to 48 h. This dose caused venular stasis and thrombus formation with subsequent involvement of arterioles. These lesions were very clear at 30 and 120 minutes after treatment. ME at 500 mg/kg BW resulted in death in up to 2 h. ME at 125 and 250 mg/kg BW did not cause death, but these doses resulted in the same changes in the microcirculatory system (thrombus formation and impairment of the arterioles) as 500 mg ME/kg. ME at 6 mg/kg increased the number of leukocytes and venular stasis, but these changes were moderate compared to the higher doses. The intensity of effects, independent of the dose, increased in proportion to the time period.