Preparative isolation and identification of tyrosinase inhibitors from the seeds of Garcinia kola by high-speed counter-current chromatography.
In continuation of our search for bioactive natural products that can be used for the treatment of dermatological disorders associated with melanin hyperpigmentation, 50 extracts/fractions from 21 families of medicinal plants from West and Central Africa were evaluated for inhibitory activity against tyrosinase (E:C:1.14.18.1), the rate-limiting enzyme in melanin synthesis. Four extracts including the methanol extract of Garcinia kola seeds at 100 microg/ml displayed >60% inhibition of tyrosinase activity. Preparative high-speed counter-current chromatography with solvent system composed of n-hexane-ethyl acetate-methanol-water (3:5:3:5) successfully separated the most active extract from G. kola seed. By stepwise increase of the flow-rate of the mobile phase, five major biflavanones including GB-I-glucoside (1) GB-1a (2), GB-1 (3), GB-2 (4), kolaflavonone (5) were successfully isolated in 6 h. Compound (4) was the most potent (IC(50) 582 microM) and compared favorably with a reference tyrosinase inhibitor (kojic acid, IC(50) 130 microM).
Okunji
Christopher
C
Biotech Center, Cook College, Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901-8520, USA.
Komarnytsky
Slavko
S
Fear
Georgie
G
Poulev
Alexander
A
Ribnicky
David M
DM
Awachie
Peter I
PI
Ito
Yoichiro
Y
Raskin
Ilya
I
D003377:Countercurrent Distribution / Q000379:methods*; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification; D029763:Garcinia kola / Q000737:chemistry*; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification*; D015203:Reproducibility of Results; D012639:Seeds / Q000737:chemistry*
D005419:Flavonoids; D010455:Peptides