Tyrosinase inhibition and antioxidant properties of Asphodelus microcarpus extracts.
BACKGROUND
Asphodelus microcarpus belongs to the family Liliaceae that include several medicinal plants. In the traditional medicine plants of the genus Asphodelus are used to treat skin disorders such as ectodermal parasites, psoriasis, microbial infection and for lightening freckles. In order to find novel skin depigmenting agents, the present work was carry out to evaluate antioxidant activity and tyrosinase inhibitory potential of leaves, flowers and tubers extracts of A. microcarpus. The phytochemical composition of the active extract was also evaluated.


METHODS
Three different extracts (water, methanol and ethanol) from leaves, flowers and tubers of A. microcarpus were evaluated for their inhibitory effect on tyrosinase activity using L-3,4-dihydroxyphenylalanine (L-DOPA) as substrate. Inhibition of cellular tyrosinase activity and melanin production was also investigated in melanoma B16F10 cells. Antioxidant activity, total phenolic and flavonoids contents were determined using standard in vitro methods. HPLC-DAD-MS was used to identify phenolic profile of the active extract.


RESULTS
The results showed that all extracts have a direct inhibitory anti-tyrosinase activity, with ethanolic extract from flowers (FEE) exhibiting the stronger effect. Kinetic analysis revealed that FEE acts as an uncompetitive inhibitor with a Ki value of 0.19 mg/mL. The same effect was observed in murine melanoma B16F10 cells. Cellular tyrosinase activity as well as melanin content were reduced in FEE-treated cells. The results were comparable to that of the standard tyrosinase inhibitor (kojic acid). Furthermore, the same extract showed the highest antioxidant activity and an elevated levels of total phenolics and flavonoid content. Eleven phenolic components were identified as chlorogenic acid, luteolin derivates, naringenin and apigenin.


CONCLUSIONS
Our findings showed that FEE from A. microcarpus inhibits tyrosinase and exerted antimelanogenesis effect in B16F10 cells. This extract also showed the highest scavenging activity, which could be mainly attributed to its high levels of total polyphenols and flavonoids. These results suggest that A. microcarpus has a great potential as sources of bioactive compounds which could be used as depigmenting agents in skin disorders.
Department of Life and Environmental Sciences, University of Cagliari, SS 554, Bivio per Sestu, I-09042 Monserrato, Cagliari, Italy.
Amalia
A
Di Petrillo
Grupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Facultad de Farmacia, Universidad de Salamanca, Salamanca, Spain.
Ana Maria
AM
González-Paramás
Department of Life and Environmental Sciences, University of Cagliari, SS 554, Bivio per Sestu, I-09042 Monserrato, Cagliari, Italy.
Benedetta
B
Era
Department of Life and Environmental Sciences, University of Cagliari, SS 554, Bivio per Sestu, I-09042 Monserrato, Cagliari, Italy.
Rosaria
R
Medda
Department of Life and Environmental Sciences, University of Cagliari, SS 554, Bivio per Sestu, I-09042 Monserrato, Cagliari, Italy. fpintus@unica.it.
Francesca
F
Pintus
Grupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Facultad de Farmacia, Universidad de Salamanca, Salamanca, Spain.
Celestino
C
Santos-Buelga
Department of Life and Environmental Sciences, University of Cagliari, SS 554, Bivio per Sestu, I-09042 Monserrato, Cagliari, Italy.
Antonella
A
Fais
D000818:Animals; D000975:Antioxidants / Q000737:chemistry*; D045744:Cell Line, Tumor; D007700:Kinetics; D019668:Liliaceae / Q000737:chemistry*; D008543:Melanins / Q000096:biosynthesis; D051379:Mice; D014442:Monophenol Monooxygenase / Q000032:analysis / Q000037:antagonists & inhibitors*; D010936:Plant Extracts / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry; D062327:Skin Lightening Preparations / Q000737:chemistry*
D000975:Antioxidants; D008543:Melanins; D010936:Plant Extracts; D062327:Skin Lightening Preparations; D014442:Monophenol Monooxygenase
Antioxidants; Asphodelus microcarpus; B16F10 melanoma cells; Flavonoids; Polyphenols; Tyrosinase inhibitors