Research Summary
Hydroxy acids are organic acids having one or more hydroxyl groups attached directly to the carbon chain of an aliphatic or alicyclic carbon atom. These acids occur in nature and can also be synthesized through chemical or enzymatic methods. Many hydroxy acids are found in plants such as sugar cane, tomatoes, oranges, lemons, grapes, and apples, as well as in animal tissues. Historically, human civilizations have used hydroxy acids in the form of crude plant extracts for treating various ailments and diseases. For instance, the ancient Sumerians and Egyptians knew about the analgesic properties of willow leaf and used its extract to cure joint pain and inflammation. Today, we understand that salicylic acid is the active ingredient in this extract (Jack, 1997).
In traditional medicine, especially in ‘Ayurveda,’ the ancient Indian science, formulations containing one or more hydroxy acids have been used as anti-aging treatments, anti-inflammatory agents, and remedies for other skin disorders (Datta et al., 2011). For decades, formulations with hydroxy acids have been used in clinical practice to treat various skin infections. These acids have broad applications in several fields, such as cosmetics (Saint-Leger et al., 2007), pharmaceuticals, and food processing (Kornhauser et al., 2010).
In cosmetics, hydroxy acids are employed for treating skin conditions like photoaging, acne, pigmentation disorders, and psoriasis (Wang, 1999; Kornhauser et al., 2010). Since their introduction into dermatology, hydroxy acids have revolutionized skin care (Van Scott & Yu, 1974; Green, 2006; Green et al., 2009). They are also precursors in synthesizing a range of pharmaceutically important chiral synthons. For example, α-hydroxyphenylacetic acid (mandelic acid) is used in producing antitumor agents (Surivet & Vatele, 1999), anti-obesity drugs, semi-synthetic penicillin (Furlenmeier et al., 1976), and cephalosporin (Terreni et al., 2001).
Hydroxy acids and their derivatives serve as useful starting materials in synthetic organic chemistry. They can be synthesized through biochemical resolution of racemates and asymmetric synthesis. Biochemical processes are often preferred over chemical ones due to their eco-friendliness, high chemo- and regio-selectivity, and better yield. However, limited information is available on the synthesis of hydroxy acids through biological routes, with only a few reports published. In this chapter, the synthesis of hydroxy acids, particularly focusing on enzymatic routes, and their applications are discussed.
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