malates

Malates are salts or esters derived from malic acid, a dicarboxylic acid commonly found in fruits. In solution, malic acid can lose one or two protons to form malate and the corresponding dianion. Common malate salts include calcium malate, potassium malate, and magnesium malate, which are used as dietary mineral supplements. Esters of malic acid are sometimes referred to as malates in some contexts.

Malic acid exists as two enantiomers, L- and D-malate, with the natural form in most organisms being L-malate. In metabolism, L-malate is a key intermediate of the citric acid cycle, formed from fumarate and subsequently converted back to oxaloacetate by malate dehydrogenase. Malate can also participate in cytosolic pathways such as the malate–aspartate shuttle, transferring reducing equivalents into mitochondria.

Plants and some microorganisms accumulate malate for carbon storage and osmoregulation; in C4 and CAM photosynthesis, malate serves as a reservoir of carbon and can be transported between cellular compartments and vacuoles to help regulate stomatal opening.

Industrial and dietary uses include mineral supplements (calcium malate, magnesium malate, and potassium malate) and, more broadly, malic acid–related ingredients used as flavorings and acidulants in foods. Malate salts are valued for relatively high mineral bioavailability; however, the acidity of malic compounds should be considered in formulation and labeling.

Malates are generally regarded as safe when used as intended in foods and supplements. They naturally occur in fruits and vegetables, and their metabolism is well characterized in biochemistry and physiology.