Antioxidant Properties and Melanin Synthesis-Inhibitory Effects of Water and Hexane Extracts of <i>Synurus deltoides</i> Leaves

Synurus deltoides, a perennial and edible plant belonging to the Compositae family, has been used as a coloring agent in food and a remedy for various inflammatory disorders in traditional medicine.Most studies on this plant have been conducted using ethanol extracts of its leaves.To further explore its biological activities, the ethanol extracts were fractionated into a hydrophilic water extract and a lipophilic hexane extract.Both extracts were then investigated for their antioxidant properties and ability to inhibit melanin synthesis.Both extracts demonstrated the ability to scavenge 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radicals and to reduce Fe(III) and Mo(VI) to Fe(II) and Mo(V), respectively.The Fe-reducing power of the water and hexane extracts was 13.10 1.01 and 8.18 1.57 mg gallic acid equivalent (GAE)/g extract, respectively, while the Mo-reducing power was 17.80 1.34 and 24.09 2.52 mg GAE/g extract, respectively.Moreover, the total phenolic content in the water and hexane extracts was 58.65 11.76 and 3.32 1.03 mg GAE/g extract, respectively.The flavonoid content was 12.12 0.46 mg catechin equivalent/g extract in the water extract, while it was undetectable in the hexane extract.Despite differences in various parameters, particularly flavonoid content, both fractions exhibited activity in all tested assays, suggesting that they are efficient antioxidants.Furthermore, both extracts inhibited tyrosinase activity, and the hexane extract specifically suppressed melanin synthesis in murine melanoma cells.These findings suggest that the 2 extracts have potential benefits in managing inflammatory skin disorders, particularly skin hyperpigmentation or skin whitening, as they work synergistically to eliminate reactive oxygen species, prevent tissue damage, and suppress melanin synthesis by inhibiting tyrosinase.