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DOI: 10.1055/s-0028-1084363
Tyrosinase inhibitors and acylated sesquiterpene diglycosides from Guioa crenulata and G. villosa
As new-Caledonian Guioa gracillis extracts are used in cosmetic and pharmaceutical preparations for the treatment of skin aging [1], we investigated the tyrosinase inhibitory activity of two Caledonian Guioa sp., G. crenulata and G. villosa. Through a bioassay-guided phytochemical investigation involving mushroom tyrosinase inhibitory activity, seven new acylated farnesyl diglycosides (Crenulatosides A-G) (1-7), five flavonoids (8-12), one trimeric proanthocyanidin (13), two triterpenes (14-15), and one cerebroside (16), were isolated from the leaves of G. crenulata [2] and G. villosa [3]. The sesquiterpene diglycosides isolated form the active EtOAc extract showed no inhibitory activity, whereas betulin (14), lupeol (15) and soyacerebroside I (16) demonstrated a potent tyrosinase inhibitory activity [3].
Structures of isolated compounds were established by means of 1D and 2D NMR experiments as well as HR-ESI-MS.
The ethanol and ethyl acetate extracts of the leaves were tested in a preliminary biological screening, but exhibited no cytotoxic activity, no inhibition of acetylcholinesterase, and no activity in the tubulin test and on topoisomerase I.
References: 1. Renimel et al. (1998) FR Patent 199961220
2. Alabdul Magid et al. (2005) Phytochemistry 66:2714–8
3. Alabdul Magid et al. (2008) Planta Med 74:55–60