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.

A methodology for the production of a saxitoxin (STX) standard from cyanobacteria (Raphydiopsis brookii strain SPC 338) was developed. The cyanobacterium was cultured in 5-litre culture bottles in ASM-1 medium, pH 7.4 at 22±1°C, under continuous light at an irradiance of 45-50 mmol m-2 s-1 and moderate aeration rate. The cells were grown until the late-exponential growth phase (approximately 3 weeks), at which point the culture was harvested. The cultured material was lyophilized, extracted with 0.1 M acetic acid and ultrasonication, and centrifuged. The supernatant was lyophilized and subjected to purification by chromatographic methods. STX purity was determined by HPLC-FLD analysis. Male Swiss-Webster mice were injected intraperitoneally with crude extract and with fractions obtained from all purification steps, all diluted in sterile 0.9% NaCl solution (the bio-guided assay). Time to death, signs of poisoning, and other symptoms were observed up to 72 h after injection. STX extracted from R. brookii showed 95% purity, which is similar to STX standards obtained from mussels. The cyanobacterium standard contains only STX, whereas the standard obtained from mollusks contains both STX and an analog. By selecting another cyanobacteria species, it may be possible to obtain different analogues at a lower price. The biomass is easily obtained in culture, its production is not seasonal, and no special storage equipment is required. Thus, this method represents an excellent option for obtaining STX standards.

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.