In this study, lyophilized and methanolic extracts of aloe gel from different germplasms were evaluated for their potential to inhibit mushroom tyrosinase activity. The results showed potent inhibitory effect of Aloe vera gel extracts on L-dihydroxyphenylalanine (L-DOPA) oxidation catalyzed by tyrosinase in a dose-dependent manner. Significant differences in % inhibition of tyrosinase among the extraction methods and the germplasms were observed. The relative performance of the germplasms was evaluated with the help of posthoc multicomparison test. The methanolic extract was more effective than the lyophilized crude gel in all the germplasms. The inhibitory effect of the lyophilized gel and methanolic extract tested from five germplasms followed the order: RM > TN > S24 > OR > RJN. The germplasm RM showed the highest tyrosinase inhibition, and the maximum % inhibition noted was 26.04% and 41.18%, respectively for the lyophilized and methanolic extracts at 6 mg · mL(-1) concentration. Lineweaver-Burk plots of the different concentrations of L-DOPA in the absence and presence of lyophilized gel extract showed competitive inhibition of mushroom tyrosinase in all the germplasms. This study suggests that the germplasm RM could potentially be used for the isolation and identification of the effective tyrosinase inhibitory component, and ascertains the critical role of selecting the best source of germplasm for natural product isolation and characterization.
Agaricales ; enzymology ; Aloe ; chemistry ; Enzyme Inhibitors ; chemistry ; Fungal Proteins ; antagonists & inhibitors ; chemistry ; Gels ; chemistry ; Kinetics ; Monophenol Monooxygenase ; antagonists & inhibitors ; chemistry ; Plant Extracts ; chemistry

OBJECTIVETo evaluate the effects of aloin, cinnamic acid and 15 other kinds of natural chemicals on the activity of tyrosinase, in order to provide lightening agents in the treatment of hyperpigmentation disorders and cosmetic additives.

METHODSTyrosinase activity was estimated by measuring the oxidation rate of L-dopa. Inhibition of the enzyme was deduced according to the Lineweaver-Burk plots compared to the control.

RESULTSCadabine, paeonal, farrerol, evodin, cinnamic acid, aloin and sophorcarpidine had different levels of inhibition of tyrosinase. The inhibitory rates of cinnamic acid (2 mmol/L, 0.5 mmol/L), aloin (2 mmol/L) and the rest were significantly higher than that of hydroquinone (0.5 mmol/L) (P < 0.05).

CONCLUSIONSTyrosinase activity can be greatly inhibited by cinnamic acid, aloin and sophorcarpidine, of which sophorcarpidine functions as an uncompetitive inhibitor, compared to aloin and cinnamic acid, which are mixed-type inhibitors.

Cinnamates ; pharmacology ; Cosmetics ; pharmacology ; Emodin ; analogs & derivatives ; pharmacology ; Enzyme Inhibitors ; pharmacology ; Humans ; Hyperpigmentation ; drug therapy ; Monophenol Monooxygenase ; antagonists & inhibitors ; Plant Preparations ; pharmacology

OBJECTIVETo isolate and identify the tyrosinase inhibitory constituent from Angelica dahurica.

METHODA tyrosinase inhibitory constituent was isolated by silica gel column chromatography combined with a bioassay-linked HPLC method.

RESULTAn extract of heat-processed A. dahurica roots showed more potent tyrosinase inhibitory activity than that of the crude drug. Tyrosinase inhibitory furanocoumarin, 8-hydroxy-5-methoxypsoralen,was isolated. It express stronger tyrosinase inhibition than the known tyrosinase inhibitor, kojic acid (IC50 = 0.0907 mmol x L(-1)) with IC50 value of 0.0086 mmol x L(-1). Therefore, it is contributive to the increased tyrosinase inhibitory activity of the heat-processed A. dahurica.

CONCLUSIONThe active constituent was 8-hydroxy-5-methoxypsoralen from the heat-processed A. dahurica.

Angelica ; chemistry ; Chromatography, High Pressure Liquid ; Enzyme Inhibitors ; analysis ; isolation & purification ; pharmacology ; Inhibitory Concentration 50 ; Monophenol Monooxygenase ; antagonists & inhibitors ; Plant Roots ; chemistry

The present paper intends to discuss the antioxidant and tyrosinase inhibition effect of solanesol from three aspects of ultraviolet radiation and free radical scavenging. The paper makes a survey on diurnal variation rule of the minimum ultraviolet transmittance and ultraviolet transmittance of solanesol, hydroxyl (OH) free radical scavenging method of Smirnoff reaction system model, superoxide anion O2- free radical scavenging method of pyrogallol autoxidation, and the inhibitory effect of solanesol on tyrosinase activity by enzyme kinetic method. The experiment results showed that solanesol could effectively scavenge lipid radicals to block lipid peroxidation, and inhibit effects on tyrosinase. Solanesol is a natural extract which could be used to prevent senile atrophy of human skin and senile plaque.
Enzyme Inhibitors ; chemistry ; Free Radical Scavengers ; chemistry ; Humans ; Hydroxyl Radical ; chemistry ; Lipid Peroxidation ; Monophenol Monooxygenase ; antagonists & inhibitors ; Terpenes ; chemistry ; Ultraviolet Rays

Tyrosinase is a key enzyme related to skin pigmentation disorders of elderly people, while self-aggregation of the amyloid-beta peptide, Abeta42, has been considered as a key event in the pathogenesis of Alzheimer's disease (AD). The present study was undertaken to investigate the inhibitory effects of 20 samples from Rhodiola species on tyrosinase and Abeta42 aggregation, and to isolate their corresponding bioactive components. The results demonstrated that the oligomeric proanthocyanidins (OPCs) commonly found in Rhodiola species were the major bioactive components corresponding to their anti-tyrosinase and anti-Abeta42 aggregation bioactivities. Salidroside, a representative compound of Rhodiola plants, proved not to be active in the present studies.
Amyloid beta-Peptides ; antagonists & inhibitors ; metabolism ; Drugs, Chinese Herbal ; isolation & purification ; pharmacology ; Glucosides ; isolation & purification ; pharmacology ; Monophenol Monooxygenase ; antagonists & inhibitors ; metabolism ; Peptide Fragments ; antagonists & inhibitors ; metabolism ; Phenols ; isolation & purification ; pharmacology ; Plant Roots ; chemistry ; Plants, Medicinal ; chemistry ; Proanthocyanidins ; isolation & purification ; pharmacology ; Rhodiola ; chemistry

Xanthohumol (XH), the principal prenylflavonoid of the hop plant (Humulus lupulus L.), dose-dependently inhibited isobutylmethylxanthine (IBMX)-induced melanogenesis in B16 melanoma cells, with little cytotoxicity at the effective concentrations. Decreased melanin content was accompanied by reduced tyrosinase enzyme activity, protein and mRNA expression. The levels of tyrosinase-related protein 1 and 2 mRNAs were decreased by XH. XH also inhibited alpha-melanocyte stimulating hormone- or forskolin-induced increases in melanogenesis, suggesting an action on the cAMP-dependent melanogenic pathway. XH downregulated the protein and mRNA expression of microphthalmia-associated transcription factor (MITF), a master transcriptional regulator of key melanogenic enzymes. These results suggest that XH might act as a hypo-pigmenting agent through the downregulation of MITF in the cAMP-dependent melanogenic pathway.
1-Methyl-3-isobutylxanthine/pharmacology ; Animals ; Cell Line ; Cell Survival/drug effects ; Dose-Response Relationship, Drug ; Down-Regulation ; Drug Antagonism ; Forskolin/pharmacology ; *Humulus ; Intramolecular Oxidoreductases/antagonists & inhibitors/biosynthesis ; Melanins/antagonists & inhibitors/*biosynthesis ; Melanocytes/*drug effects/*metabolism ; Melanoma, Experimental ; Membrane Glycoproteins/antagonists & inhibitors/biosynthesis ; Mice ; Microphthalmia-Associated Transcription Factor/antagonists & inhibitors ; Monophenol Monooxygenase/antagonists & inhibitors/biosynthesis/genetics ; Oxidoreductases/antagonists & inhibitors/biosynthesis ; Propiophenones/*pharmacology ; Signal Transduction/drug effects ; alpha-MSH/metabolism