Investigation of in vitro HDAC 1 inhibitory activity of Curcuma longa L. extracts, isolated fractions and curcumin

Histone deacetylases are a group of enzymes that have been linked with various inflammatory, cancerous and hereditary diseases. In this study, turmeric extracts and isolated fractions were investigated specifically for in vitro HDAC 1 inhibitory activity. Crude extracts (hexane, dichloromethane, 2-MeTHF, ethanol, 70% ethanol and water) covering a wide range of polarity were screened. Quantitative analysis of total phenol, flavonoid content and curcuminoids were performed using spectrophotometry and UPLC-DAD, ESI–MS/MS. Among the crude extracts, dichloromethane yielded the highest total phenol and flavonoid content along with curcuminoids (177.82 mg CE/g). Curcumin was the major curcuminoid followed by bis-demethoxycurcumin and demethoxycurcumin. 2-MeTHF, a greener biobased solvent alternative, presented similar bioactive content and HDAC 1 inhibitory activity compared to dichloromethane. Despite the results of crude extracts, the highest amounts of curcuminoids were isolated in 25:75 water:ethanol fraction of the 70% ethanol extract, which also possessed the strongest HDAC 1 inhibitory activity (IC 50 : 7.70 µg/ml) where curcumin alone (IC 50 : 3.75 µg/ml, 10.18 µM) showed remarkable potency. To the best of our knowledge, this is the first study comparatively revealing in vitro HDAC 1 inhibitory potential of Curcuma longa L. extracts and isolated fractions. In future studies, the curcuminoid-rich fraction can be evaluated for use in products as a supplement or nutraceutical, that may be beneficial against the HDAC related disorders.