Metanephrine (metadrenaline) is a metabolite of epinephrine (adrenaline) created by the action of catechol-O-methyl transferase on epinephrine. It is a commonly occurring, pharmacologically and physiologically inactive metabolite of epinephrine. The measurement of plasma free metanephrines is considered to be the best tool in the diagnosis of pheochromocytoma, a rare kind of adrenal medullary neoplasm. In adrenal chromaffin cells, leakage of norepinephrine and epinephrine from storage granules leads to the substantial intracellular production of the O-methylated metabolite metanephrine. In fact, the adrenals constitute the single largest source out of any organ system including the liver for circulating metanephrine. In humans, about 93 percent of circulating metanephrine is derived from catecholamines metabolized within adrenal chromaffin cells.

S-Adenosyl-L-homocysteine (SAH), a potent methyltransferase inhibitor and a substrate of the s-adenosylhomocysteine hydrolase, is an amino acid derivative and an intermediator or modulator of several metabolic pathways, including the activated methyl cycle and cysteine biosynthesis. It was shown, that the plasma SAH might be a novel biomarker for the early clinical identification of cardiovascular disease. In addition, the elevated SAH in Alzheimer's brain was related to markers of disease progression and cognitive impairment.

L-alloisoleucine (2S, 3R), a diastereomer of L-isoleucine (2S, 3S), is a normal constituent of human plasma. It was shown, that the plasma L-alloisoleucine above the cutoff value of 5 micromol/L is the most specific and most sensitive diagnostic marker for all forms of maple syrup urine disease (MSUD). The precise mechanism of L-alloisoleucine formation is unclear, but existed suggestions, that R-3-methyl-2-oxopentanoate is an immediate and inevitable byproduct of L-isoleucine transamination and that alloisoleucine is primarily formed via transamination of 3-methyl-2-oxopenanoate in vivo.

Natural perseitol is to be named D-perseitol because it was synthesized through the reduction of D-manno-D-gala-heptose. D-perseitol would surely result also from the reduction of L-gala-D-manno-heptose. It was demonstrated that perseitol with a configuration of the hydroxyl group at the 4th carbon atom corresponding to that of mannoheptulose showed a significant inhibition of glucokinase. A complex of perseitol (D-glycero-D-galacto-heptitol) and K+ ions, isolated from the leaves of Scurrula fusca (Loranthaceae), which has been traditionally used for the treatment of cancer in Sulawesi Island (Indonesia), exhibits a potent inhibitory effect on [3H]-leucine incorporation for protein synthesis in Ehrlich ascites tumor cells in mice. Transaldolase-deficient patients had subtle elevations of perseitol in urine. Thus, heptitol perseitol might serves as novel urinary biomarkers for identification of transaldolase deficiency.