Molecular modification approach on kojic acid derivatives as antioxidants related to ascorbic acid

Antioxidant capacity of simplified oxygen heterocycles and proposed derivatives by theoretical calculations

CONTEXT

Some structural properties can be involved in the antioxidant capacity of several polyphenol derivatives, among them their simplified structures. This study examines the contribution of simplified structure for the antioxidant capacity of some natural and synthetic antioxidants. The resonance structures were related to the π-type electron system of carbon-carbon double bonds between both phenyl rings. Trans-resveratrol, phenyl-benzofuran, phenyl-indenone, and benzylidene-benzofuranone are the best basic antioxidant templates among the simplified derivatives studied here. Additionally, the stilbene moiety was found on the molecules with the best antioxidant capacity. Furthermore, our investigation suggests that these compounds can be used as antioxidant scaffold for designing and developing of new promising derivatives.

METHODS

To investigate the structure-antioxidant capacity for sixteen simplified natural and proposed derivatives we have employed density functional theory and used Gaussian 09. Our DFT calculations were performed using the B3LYP functional and the 6-31+G(d,p) basis set. All electron transfer mechanisms were investigated by using values of HOMO, ionization potential, energy affinity, stabilization energies, and spin density distributions.

Fungal production of kojic acid and its industrial applications

Kojic acid has gained its importance after it was known worldwide that the substance functions primarily as skin-lightening agent. Kojic acid plays a vital role in skin care products, as it enhances the ability to prevent exposure to UV radiation. It inhibits the tyrosinase formation which suppresses hyperpigmentation in human skin. Besides cosmetics, kojic acid is also greatly used in food, agriculture, and pharmaceuticals industries. Conversely, according to Global Industry Analysts, the Middle East, Asia, and in Africa especially, the demand of whitening cream is very high, and probably the market will reach to $31.2 billion by 2024 from $17.9 billion of 2017. The important kojic acid-producing strains were mainly belongs to the genus Aspergillus and Penicillium. Due to its commercial potential, it continues to attract the attention for its green synthesis, and the studies are still widely conducted to improve kojic acid production. Thus, the present review is focused on the current production processes, gene regulation, and limitation of its commercial production, probable reasons, and possible solutions. For the first time, detailed information on the metabolic pathway and the genes involved in kojic acid production, along with illustrations of genes, are highlighted in the present review. Demand and market applications of kojic acid and its regulatory approvals for its safer use are also discussed. KEY POINTS: • Kojic acid is an organic acid that is primarily produced by Aspergillus species. • It is mainly used in the field of health care and cosmetic industries. • Kojic acid and its derivatives seem to be safe molecules for human use.

Essential features for antioxidant capacity of ascorbic acid (vitamin C)

Vitamin C or ascorbic acid is an indispensable micronutrient for human health found principally on citrus species such as lemon and orange fruits and vegetables. It was involved in the production of proteins such as collagen. Its biochemical mechanism is related to its antioxidant capacity; however, its function at the cellular level is still unclear. Several theoretical studies about antioxidant and redox mechanisms for ascorbic acid were suggested; however, no derivative was proposed. Thereby, an electronic study of antioxidant capacity for ascorbic acid derivatives was performed using theoretical chemistry at the DFT/ B3LYP/6-311 +  + (2d,2p) level of theory. Simplified derivatives show that enol hydroxyls are more important than any other functional group. The vicinal enolic hydroxyl on β position is more important for antioxidant capacity of ascorbic than hydroxyl on α position. According to our molecular modifications, the keto-alkene compound showed the best values when compared to ascorbic acid in some molecular characteristics. No lactone derivatives have superior application potential as antioxidant when compared with ascorbic acid. Several structures are possible to be proposed and were related to spin density contributions and the increase of chemical stability. New promising structural derivatives related to ascorbic acid can be developed in the future.