In the foremost chapter of Indole: Synthesis, Functions and Reactions, derivatives of hydrogenated pyrido[4,3-b]indoles as potential neuroprotectors have been synthesized. Different substituents were introduced into position 8 of the carboline fragment of the molecule: methyl-, methoxy-, fluorine- and chlorine-ones. Biological tests have shown that all the studied compounds can modulate glutamate-dependent uptake of calcium ions in rats' cerebral cortex synaptosomes. The authors go on to discuss how mushrooms and their mycelia from in vitro cultures have become increasingly common study subjects due to their health-promoting potential. The most frequently demonstrated properties of these mushrooms include antioxidative, anticancer, anti-inflammatory, immunostimulatory and anti-depressive effects. This activity stems from numerous mushroom metabolites, bioelements and physiologically active substances, including indole compounds. The final chapter provides an overview of the diverse synthetic approaches to generate pyrimido[4,5-b]indoles. Pyrimido-indoles are tricyclic ring systems produced when an indole group is fused with a pyrimidine ring. Of the two possible isomers of this ring system, the pyrimido[4,5-b]indoles are of particular interest relative to pyrimido[5,4-b]indoles due to their presence in a wide range of pharmacologically active molecules.