Phytochemical and anti-tyrosinase studies were performed on the stems
of Anaxagorea luzonensis A. Gray, collected from a forest area in Petchaburee
Province, Thailand. The hexane, dichloromethane and ethyl acetate extracts were
found to be active against mushroom tyrosinase with percent inhibition at 0.909
mg/ml of 28.56 %, 58.27 % and 86.76 %, respectively. Results also confirmed the
antioxidant activities of these extracts as shown by the IC50 values of 162.7, 10.60
and 3.33 ug/ml, respectively. Bioassay-guided fractionation of these extracts was
carried out by chromatographic methods. Phytochemical investigation of these
extracts resulted in the isolation and identification of five compounds; the three
xanthones were found to be 1,6-dihydroxy-5-methoxy-4',5'-dihydro-4',4',5'-
trimethyl-furano-(2',3':3,4)-xanthone (A), 2-deprenyl-rheediaxanthone B (B) and
1,3,6-trihydroxy-5-methoxyxanthone(C) and the two flavonols were identified as
kaempferol (D) and quercetin (E). Their structures were established by
spectroscopic methods (UV, IR, MS, 1H-NMR and 13C-NMR). This is the first
report on the anti-tyrosinase activity of the A. luzonensis, compounds A (IC50 1.18
mM) and B (IC50 1.35 mM), while compound D (kaempferol) and E (quercetin),
are known anti-tyrosinase agents. These compounds exhibited scavenging activity
toward DPPH radical with IC50 values of 5.56 (A), 7.62 (B), 6.94 (D) and 5.30 (E)
uM. However, compound C was found to be inactive against mushroom tyrosinase
and to have little free radical scavenging activity.
The results of this study demonstrated the potential of A.luzonensis as
tyrosinase inhibitory and antioxidant agents for applications in the pharmaceutical
and cosmeceutical fields.
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