AbstvactThe contents of the steroidal alkaloid solasodine and of solasodine-like alkaloids in samples of 85 native Australian Solanum species have been determined. Leaf, stem and fruit of 74, leaf and stem of seven, and leaf only of four species were examined. Samples were extracted with ethanol, the resulting glycoalkaloids were hydrolysed and the amount of alkaloidal aglycone was estimated by a colorimetric procedure based on solasodine as the standard. The solasodine present in the extracts was identified by comparison with an authentic sample by means of thin-layer chromatography. Twenty-nine Australian species were shown to contain appreciable amounts of solasodine. Of all the species examined, S. aviculare, S. laciniatum and S, simile were found to have the highest content of solasodine. Tomatidine has been isolated from S, dimovphospinum. S, callium contains appreciable quantities of the two new alkaloids 25-isosolafloridine and solacallinidine. S, dunalianum, which has probably been introduced into Australia from New Guinea, contains the new alkaloid soladunalinidine and small amounts of tomatidine.

Liquid extraction is one means of removing metabolic products continuously during a fermentation and so reducing product inhibition. It is known that microbial organisms are attracted to liquid-liquid interfaces, and it is important for the design of extraction systems to establish if this has a detrimental effect on the rate of extraction. The extraction of ethanol from aqueous suspensions of yeast (Saccharomyces cerevisiae) using n- decanol is described in this paper. It was found that the presence of the yeast cells severely reduced the rate of ethanol extraction. The overall mass transfer coefficient was reduced from 5.0 x 10(-6) to 0.7 x 10(-6) m/s. This reduced overall mass transfer coefficient was unaffected by yeast concentration in the range 0.1-20 kg/m(3). The results are consistent with the yeast cells adsorbing to the interface in closely packed layers and preventing mass transfer by simply reducing the available interfacial area. Optical microscope observations confirmed that a yeast layer several cell diameters thick rapidly built up at the interface when a small decanol droplet was added to a yeast suspension.