Benzylpenilloic acid is a metabolite of benzylpenicillin. It is produced by hydrolysis of when beta-lactam ring of benzylpenicillin. Along with some other metabolites of penicillin, benzylpenilloic acid is responsible for the allergic reaction to beta-lactam antibiotic. It is a component of a minor determinant mixture (MDM) reagent which is used to evaluate sensitivity to penicillin in the clinic.

Kifunensine is an immunoactive compound originally produced by Kitasatosporia kifunense, which displays competitive inhibition against immunosuppressive factor in tumor-bearing mice. Kifunensine has also been shown to be a potent inhibitor of the purified glycoprotein processing enzyme, mannosidase I (MAN1), specifically MAN1A1, MAN1A2, MAN1B1 and MAN1C1. Kifunensine inhibits human endoplasmic reticulum α-1,2-mannosidase I and Golgi Class I mannosidases IA, IB and IC with Ki values of 130 and 23 nM, respectively. Enzymes of this class are important factors for the biosynthesis of various types of N-linked oligosaccharide structures. Inhibition of these structures by kifunensine can interfere with cell-to-cell adhesion, targeting of lysosomal hydrolases to lysosomes, and clearance of asialoglycoproteins from the serum. Kifunensine is used to suppress Endoplasmic Reticulum-Associated Degradation (ERAD) via the inhibition of endoplasmic reticulum-associated mannosidase activity. Kifunensine has shown potential for treatment of sarcoglycanopathies and lysosomal storage disorders. Orphan designation (EU/3/11/906) was granted by the European Commission to Généthon, France, for kifunensine for the treatment of beta sarcoglycanopathy, but it was withdrawn later. Kifunensine’s use as a therapeutic is currently being researched in several conditions that benefit from its ability to inhibit mannosidase I.

Echinocandin B is a naturally occurring antibiotic, isolated from Aspergillus nidulans. It acts as an inhibitor of fungal β-1,3-glucan synthase thereby disrupting the formation of the fungal cell wall. The drug itself was not developed in the clinic, but instead, it was used in the production of other echinocandin derivatives.

Aphidicolin, a tetracyclic diterpenoid obtained from the culture filtrates of Cephalosporium aphidicola and other fungi, inhibits the growth of eukaryotic cells and of certain animal viruses (SV40, Herpes and Vaccinia viruses) by selectively inhibiting the cellular replicative DNA polymerase alpha or the viral-induced DNA polymerases. The arrest of cellular or viral growth is thus due to inhibition of cellular or viral replicative DNA synthesis without interference with mitochondrial DNA synthesis, RNA, protein and nucleic acid precursors synthesis or other major metabolic pathways. The inhibition of all sensitive eukaryotic DNA polymerases by aphidicolin is competitive with respect to dCTP. Aphidicolin has thus proved extremely useful in elucidating the functional role of DNA polymerase alpha in nuclear DNA replication, of DNA polymerase gamma in mitochondrial DNA synthesis and both DNA polymerases beta and alpha in DNA repair synthesis. An important laboratory application of aphidicolin is the synchronization of the cell cycle of eukaryotic cells both in culture and in vivo. The properties of aphidicolinhave recently aroused considerable interest for its possible exploitation in al practice. The mechanism of action of this drug suggests in fact that it may be useful for controlling excessive cell proliferation in patients with cancer, psoriasis or other dermatitis with little or no adverse effect upon non-multiplying cells.

THYMIDINE 5'-MONOPHOSPHATE (or thymidine monophosphate, or TMP), a substrate of thymidylate kinase, transforms into the thymidine diphosphate that is essential in both the de novo and salvage pathways of DNA synthesis of the thymidine triphosphate. In mammalian cells, thymidine deprivation induces chromosome aberrations such as chromatid breaks, chromatid interchanges, and chromosome fragmentation.