Purpose
This study aimed to determine the extent of contribution of dopamine to antioxidant and anti-tyrosinase activities, by dopamine addition to vanillin. This study achieved the synthesis of dopamine-associated vanillin Mannich base derivatives prepared via a one-step reaction involving a green chemistry approach, and investigation of antioxidant and anti-tyrosinase activities.
Methods
Novel one-pot synthesis of Mannich base dopamine-connected vanillin (
1a-l
) derivatives can be achieved via green chemistry without using a catalyst. Newly-prepared compounds were characterised with FTIR and NMR (
1
H and
13
C) spectra, mass spectra, and elemental analyses. In total, 12 compounds (
1a-l
) were synthesised and their antioxidant and anti-tyrosinase activities evaluated. Antioxidant activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO), hydrogen peroxide (H
2
O
2
), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and diammonium assays, ABTS
•+
radical scavenging, and linoleic acid peroxidation were used to screen all synthesised compounds (
1a-l
) for anti-tyrosinase activities and cytotoxicity against MCF-7 and Vero cell lines;.
Results
The compound
1k
inhibited (IC
50
:11.02µg/mL) the DPPH-scavenging activity to a greater extent than the standard BHT (IC
50
:25.17µg/mL), and showed high activity in H
2
O
2
and NO scavenging assays. Compound
1e
was more potent (96.21%) against ABTS and compound
1k
was more potent (95.28%) against 2,2ʹ-azobis(2-amidinopropane)dihydrochloride antioxidant than the standard trolox. All synthesised compounds were screened for anti-tyrosinase inhibitory activity. Compound
1e
had higher activity against tyrosinase (IC
50
=10.63 µg/mL), than kojic acid (IC
50
=21.52µg/mL), and was more cytotoxic (GI
50
0.01µM) against MCF-7 cell line than the doxorubicin standard and other tested compounds.
Conclusion
In this study, all compounds were found to possess significant antioxidant and anti-tyrosinase activities. Compounds
1e
and
1k
performed well, compared with other compounds, in all assays. In addition, this study successfully identified several promising molecules that exhibited antioxidant and anti-tyrosinase activities.
