The Free Radical Scavenging and Tyrosinase Inhibition Activities of Protocatehuic Acid and Caffeic Acid Derivatives
Chau-Chen Yang*, Ching-Gong Lin, Zong-Shiow Chen
Institute of Cosmetic Science, Chia-Nan University of Pharmacy and Science, 60 Erh-Jen Road, Sec.1, Jen-Te, Tainan 717, Taiwan.
Objects
The most current research on antioxidant action focuses on phenolic compounds. They are the most common compounds in fruits and vegetables and have a strong antioxidant capacity. Caffeic acid (3, 4-dihydroxycinnamic acid) is among the major hydroxycinnamic acids present in many kinds of fruits. Protocatehuic acid belongs to the hydroxybenzoic acid has also been identified as one of the active antioxidants. In the present study, the antioxidant properties of the caffeic acid and protocatehuic acid derivatives were synthesized and evaluated by using different in vitro antioxidant assays such as 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH•) scavenging and DNA protection activities. The effective antioxidants were also surveyed of the tyrosinase inhibition activity.
Keywords free radical scavenging, tyrosinase inhibition, protocatehuic acid, caffeic acid, esterification, amidization
Conclusion
As seen in results, compounds 1, 2, 5, 6 (esterification derivatives of protocatehuic acid) had effective DPPH•
scavenging activity in a concentration dependent manner (1–50 μg/mL). There is a significant decrease in the concentration of DPPH•due to the scavenging capacity of these compounds. Present study has clearly shown that two protocatehuic acid derivatives, compounds 1 (methyl 3, 4- dihydroxy benzoate) and 2 (ethyl 3, 4- dihydroxy benzoate), were effective antioxidants in different in vitro antioxidant assays including total antioxidant activity by DPPH•
scavenging and DNA protection assays. In addition, compounds 6 and 7 derived from protocatehuic acid were potent tyrosinase inhibitors.
Acknowledgement
The authors thank Dr. Scott Valentine for proofreading the manuscript and Ms. Che-Hsiu Tsai for technique assistance. We also thank Chia-Nan University of Pharmacy and Science and Ministry of Education for financial supports.
Materials and methods
Esterification and amidization reactions for the syntheses of the protocatehuic acid and caffeic acid derivatives were illustrated in Figure 1.
Control UV 10-1 10-2 8x10-3 6x10-3 4x10-3 2x10-3 10-3 10-4
