L-ascorbic acid (ascorbic acid) is the conjugate acid of L-ascorbate and the L enantiomer of ascorbic acid. is a chemical compound, a synthesized vitamin C. 

The name describes the structure of the molecule:

• L- refers to the configuration of the ascorbic acid molecule. In chemistry, the terms 'L-' and 'D-' are used to indicate the configuration of a molecule around a specific chiral centre. In the case of ascorbic acid, the 'L-' form is the one that is biologically active and used in food supplements and additives.
• Ascorbic acid. The term 'ascorbic' is derived from 'a-' (meaning 'no') and 'scorbutus' (the Latin word for scurvy), because ascorbic acid is effective in the prevention and treatment of scurvy.

The synthesis of L-ascorbic acid can be achieved by different methods, but one of the most common is the Reichstein process, which involves the following steps:

• Sorbitol fermentation. Sorbitol, a sugar alcohol, is fermented by bacteria to produce L-sorbose.
• Oxidation. L-sorbose is then oxidised to 2-keto-L-gulonic acid (2-KGA) using a microorganism or enzyme.
• Ring closure: 2-KGA is then heated under acidic conditions to cause ring closure, forming L-ascorbic acid.

What it is for and where

Medical

While vitamin C is an organic compound, ascorbic acid is the purest form of vitamin C, but it is a chemical compound, a synthesized form of vitamin C. Both have the same molecular formula C₆H₈O₆ or Hc₆H₇O₆

Let's talk about ascorbic acid and then we'll talk about vitamin C.

Ascorbic acid is not only an antioxidant, but has some biosynthetic peculiarities in different organisms as a co-substrate of several dioxygenases, a particular function in gene expression, the important role of regenerative enzymes, modulator of neuronal metabolism. It plays a key role in endogenous antioxidant defense and is cofactor in the production of carnitine and collagen.

Ascorbic acid insufficiency can occur in conditions of systemic oxidative stress, inflammation, sepsis, trauma. 

Many clinical and laboratory studies have established the effects of ascorbic acid in the treatment and prevention of cancer, with inhibition of prostate, ovarian, and pancreatic cancer cell growth, neuroblastoma cells, and inhibition of liver cancer growth and metastasis (1). However, L-ascorbic acid is a highly unstable compound and its use in pharmaceuticals and cosmetics, particularly at higher concentrations, is limited.

Cosmetics

Antioxidant agent. Ingredient that counteracts oxidative stress and prevents cell damage. Free radicals, pathological inflammatory processes, reactive nitrogen species and reactive oxygen species are responsible for the ageing process and many diseases caused by oxidation.

Buffering agent. It is an iingredient that can bring an alkaline or acid solution to a certain pH level and prevent it from changing, in practice a pH stabiliser that can effectively resist instability and pH change.

Fragrance. It plays a decisive and important role in the formulation of cosmetic products as it provides the possibility of enhancing, masking or adding fragrance to the final product, increasing its marketability. It is able to create a perceptible pleasant odour, masking a bad smell. The consumer always expects to find a pleasant or distinctive scent in a cosmetic product. 

Skin conditioning agent. It is the mainstay of topical skin treatment as it has the function of restoring, increasing or improving skin tolerance to external factors, including melanocyte tolerance. The most important function of the conditioning agent is to prevent skin dehydration, but the subject is rather complex and involves emollients and humectants that can be added in the formulation.

For more information:

L-ascorbic acid studies

Commercial ascorbic acid occurs as a fine white or nearly white crystalline powder or colorless crystals

Typical optimal characteristics of commercial L-ascorbic acid product

• Molecular Formula: C₆H₈O₆     HC₆H₇O₆
• Molecular Weight: 176.12  g/mol
• CAS: 50-81-7
• UNII PQ6CK8PD0R
• EC Number: 200-066-2    477-330-0
• DSSTox Substance ID: DTXSID5020106
• MDL number  MFCD00064328
• PubChem Substance ID 329749065
• InChI=1S/C6H8O6/c7-1-2(8)5-3(9)4(10)6(11)12-5/h2,5,7-10H,1H2/t2-,5+/m0/s1
• InChl Key      CIWBSHSKHKDKBQ-JLAZNSOCSA-N
• SMILES    C(C(C1C(=C(C(=O)O1)O)O)O)O
• IUPAC   (2R)-2-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxy-2H-furan-5-one
• ChEBI    29073

Synonyms:

• L(+)-Ascorbic acid
• l-ascorbic acid
• vitamin C
• Ascorbate, Sodium

Vitamin C is a water-soluble vitamin that must be consumed from external sources (mainly fruits and vegetables) because humans cannot synthesize it endogenously, whereas some animals can. From a health perspective, however, while dietary vitamin C from food has a protective association from early atherosclerosis, unfortunately, taking vitamin C supplements has an adverse association (2).

Vitamin C is is a simple low molecular weight carbohydrate and is necessary for tissue growth and repair in all parts of the body. The United States Institute of Medicine recommends a daily vitamin C intake of 75 milligrams per day for adult women and 90 milligrams per day for adult men.

Vitamin C It is used by our body to:

• make an important protein for skin, tendons, ligaments and blood vessels.
• heal wounds and scars.
• repair and maintain healthy cartilage, bones and teeth.
• In the food industry it is labeled as E300 in European food additives.

In the food industry it is labeled as E300 in European food additives.

In the human body it is used for the maintenance of the antioxidant defenses of the cell, it is a free radical scavenger. It also performs the important function of contributing to vitamin E regeneration. Vitamin C also cycles between an oxidized form (L-dehydroascorbic acid) and a reduced form (L-ascorbic acid). In addition, vitamin C is important for the absorption and metabolism of iron.

Vitamin C is one of many antioxidants. Antioxidants are substances that block some of the damage caused by free radicals.

Free radicals are formed when the body is in particular uncomfortable conditions, for example, when exposed to smoke or radiation, when ingesting too much saturated fat, etc. The accumulation of free radicals over time is largely responsible for the aging process. Free radicals can play a role in cancer, heart disease and arthritis.

The body is unable to produce vitamin C on its own and does not store it, therefore, it is important to get a certain amount of vitamin C from foods that contain it, daily.

It is used, in medicine, in the treatment of colds and flu.

In nature it is found in :

• Citrus fruits and juices, such as orange, lemon, grapefruit  
• Kiwi   
• Acerola
• Mango
• Papaya
• Pineapple
• Strawberries, raspberries, blueberries, cranberries
• Watermelon
• etc

References________________________________________________________________________

(1) Wan J, Zhou J, Fu L, Li Y, Zeng H, Xu X, Lv C, Jin H. Ascorbic Acid Inhibits Liver Cancer Growth and Metastasis in vitro and in vivo, Independent of Stemness Gene Regulation. Front Pharmacol. 2021 Aug 24;12:726015. doi: 10.3389/fphar.2021.726015. 

(2) Agarwal M, Mehta PK, Dwyer JH, Dwyer KM, Shircore AM, Nordstrom CK, Sun P, Paul-Labrador M, Yang Y, Merz CN. Differing Relations to Early Atherosclerosis between Vitamin C from Supplements vs. Food in the Los Angeles Atherosclerosis Study: A Prospective Cohort Study. Open Cardiovasc Med J. 2012;6:113-21. doi: 10.2174/1874192401206010113.