This work includes three studies: 1) Two methylated sterols, 4,14-dimethylergosta-8,24(28)-diene-3-ol and 14-methylergostadiene-3β-ol, were identified in yeasts, which is the first time methylated sterols have been detected in strains without disturbed 14α-demethylase function. 2) Continuing the chemical study of Vinca major L. introduced into Georgia, the hypogeal organs were investigated for alkaloids; 1.3 kg of roots collected in secondary autumn flowering yielded 0.385% purified alkaloids, and four bases (vincamajoreine, vincamajine, reserpinine, majdine) were isolated and identified. 3) The influence of Mg²+ ions on the hydrolytic capacity of cotton plant alkaline pyrophosphatase was studied, showing Mg²+ activates the enzyme in all tested concentrations (optimum 5 mM), with higher concentrations decreasing enzyme activity.