Flavonols from saffron flower: tyrosinase inhibitory activity and inhibition mechanism.
Kubo I,Kinst-Hori I
Journal of agricultural and food chemistry
A common flavonol, kaempferol, isolated from the fresh flower petals of Crocus sativus L. (Iridaceae) was found to inhibit the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) catalyzed by mushroom tyrosinase with an ID(50) of 67 microgram/mL (0.23 mM). Interestingly, its 3-O-glycoside derivatives did not inhibit this oxidation. The inhibition kinetics analyzed by a Lineweaver-Burk plot found kaempferol to be a competitive inhibitor, and this inhibitory activity presumably comes from its ability to chelate copper in the enzyme. This copper chelation mechanism can be applicable for all of the flavonols as long as their 3-hydroxyl group is free. However, quercetin, kaempferol, and galangin each affect the oxidation of L-tyrosine in somewhat different ways.
A comprehensive appraisal on Crocus chrysanthus (Herb.) Herb. flower extracts with HPLC-MS/MS profiles, antioxidant and enzyme inhibitory properties.
Zengin Gokhan,Aumeeruddy Muhammad Zakariyyah,Diuzheva Alina,Jekő József,Cziáky Zoltán,Yıldıztugay Aysegul,Yıldıztugay Evren,Mahomoodally Mohamad Fawzi
Journal of pharmaceutical and biomedical analysis
In the quest for new drugs of herbal origin, the ethyl acetate (EAE), methanol (ME), and water (WE) extracts of Crocus chrysanthus (Herb.) Herb. flowers were analyzed for their polyphenolic composition, antioxidant, and enzyme inhibitory potential. WE showed the highest antioxidant activities in all assays including metal chelating, phosphomolybdenum, FRAP, CUPRAC, ABTS and DPPH. EAE was the most effective enzyme inhibitor, exhibiting the highest inhibition against some enzymes linked to Alzheimer's disease (cholinesterases), diabetes mellitus (α-glucosidase and α-amylase) and hyperpigmentation problems (tyrosinase). The highest total phenolics (34.99 mg GAE/g) and flavonoids content (77.58 mg RE/g) were observed in WE and ME, respectively. Eight compounds were identified in EAE, 24 in ME, and 15 in WE. Kaempferol 3-O glucoside was found in all extracts. In conclusion, C. chrysanthus flowers can be suggested as a source of bioactive components with potential use against chronic disorders caused by oxidative stress. Future in-depth studies are recommended to determine the biological effects of isolated compounds from C. chrysanthus to identify the main compounds modulating the observed activities.