BioArena as a complex bioautographic system was successfully used for studying mechanism of action of some characteristic plant ingredients (e.g., 1'-methyl-ascorbigen, trans-resveratrol, salicylic acid, cinnamic acid). It has been established that the formaldehyde as a main component of formaldehyde cycle and other biochemical pathways can be studied in chromatographic spots as well. Ozone as a specially reactive reaction product of formaldehyde can be measured indirectly there. Different formaldehyde-capturing and -giving molecules and other compounds influenced (inhibited or promoted) characteristically the antibiotic effect.