The phosphonic acid functional group, which is characterized by a phosphorus atom bonded to three oxygen atoms (two hydroxy groups and one P=O double bond) and one carbon atom, is employed for many applications due to its structural analogy with the phosphate moiety or to its coordination or supramolecular properties. Phosphonic acids were used for their bioactive properties (drug, pro-drug), for bone targeting, for the design of supramolecular or hybrid materials, for the functionalization of surfaces, for analytical purposes, for medical imaging or as phosphoantigen. Potassium salt of phosphonic acid can be a declared or undeclared component of (foliar) fertilizers or plant strengtheners that were authorized in organic farming.

2,5-Dimethyl-N-Phenyl-3H-diazaphophol-4-imine is a quinonoid tautomer of GABAA and GABAB agonist progabide. According to quantum mechanical calculations, a quinonoid form is predominant in polar solvents, while aromatic tautomer is prevalent in apolar solvents. Progabide is a prodrug of gamma-aminobutyric acid and was investigated for the treatment of epilepsy, Parkinson's disease, schizophrenia, clinical depression, anxiety disorder, and other diseases. Progabide was marketed in France by Sanofi Aventis under tradename Gabrene for use in monotherapy and also as adjunctive therapy for generalized tonic-clonic, myoclonic, partial seizures, and for Lennox‐Gastaut syndrome, in both children and adults.

Doconexent (Docosahexaenoic acid, DHA) is an omega-3 fatty acid that is a primary structural component of the human brain, cerebral cortex, skin, and retina. DHA is widely used as a food supplement, and is beleived to support healthy brain development in young childred, prevent cardiovascular disease and cognitive decline during Alzheimer's disease. Most of these claims, however, were not supported by clinical trials. DHA spray is used as a tanner.

Erythorbic acid, an epimer of L-ascorbic acid, is used in the United States as a food additive. It was studied, that erythorbic acid enhanced of iron absorption and could play a major role in enhancing iron bioavailability from mixed diets that include foods preserved with erythorbic acid. In addition, was investigated if the erythorbic acid could influence on the metabolism of vitamin C in young women, and obtained results showed, that prolonged ingestion of erythorbic acid had no effect on vitamin C uptake or clearance from the body.

Gentisic acid is an active metabolite of salicylic acid degradation, which possesses a broad spectrum of biological activity, such as anti-inflammatory, antirheumatic and antioxidant properties. The antioxidant activity and radioprotective properties of gentisic acid are exerted by its phenoxyl group. It is also used in cosmetics as a skin-whitening agent for the treatment of skin pigmentary disorders by influencing the synthesis of melanin through inhibition of melanosomal tyrosinase activity Gentisic acid is also a biomarker of Renal Cell Carcinoma.

2-Methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulfonic acid (AMPS) is an fda approved for use in polymer components of food-contact paper and board adhesive. Poly(2-acrylamido-2-methyl-1-propanesulfonic acid)(PAMPS)] has been found to inhibit the cytopathicity of HIV-1 and HIV-2 in MT-4 cells at concentrations that are not toxic to the host cells. It also inhibited syncytium formation in co-cultures of MOLT-4 cells with HIV-1- or HIV-2-infected HUT-78 cells. It inhibited binding of anti-gp120 mAb to HIV-1 gp120 and blocked adsorption of HIV-1 virions to MT-4 cells.

Medronic acid (conjugate base, medronate) is a diagnostic agent that is used in complex with technetium Tc-99m for imaging delineate areas of altered osteogenesis. Upon administration the complex binds to hydroxyapatite crystals in bone.