Inhibition of lipoxygenase-1 by tetrahydrocurcumin

Synthesis, characterization and anti-inflammatory properties of karanjin (Pongamia pinnata seed) and its derivatives

Karanja (Pongamia pinnata) is a medicinal tree used in the Indian traditional ayurvedic system for treating several ailments. The seeds contain a unique furano-flavonoid karanjin, which has shown to possess many medicinal properties. Its usage at the clinical level is affected due to poor solubility and absorption. In the present investigation, molecular modifications of karanjin were attempted and evaluated their effect on anti-inflammatory activity. Firstly, Karanja ketone was obtained from karanjin by hydrolysis, and it was converted into karanja ketone oxime. The oxime undergoes Beckmann rearrangement and cyclized to yield furano benzoxazole (karanja oxazole). The new derivatives were purified with >95% purity (HPLC) and spectrally characterized (HR-MS, FTIR, and NMR). Among the test compounds, karanja ketone oxime exhibited higher antioxidant activity with an IC50 value of 360 µg/ml (DPPH). Soy lipoxygenase-1 (LOX-1) inhibitory activity of oxime was higher (IC50 = 65.4 µM) than other compounds. Fluorescence studies showed that oxime had higher quenching capacity with a Qmax of 76.3% and a binding constant of 0.9 × 105 M-1 for soy LOX-1. In-silico interaction studies showed that karanja ketone oxime had the least binding energy of -5.76 kcal/mol with LOX-1 by forming two hydrogen bonds with hydrophobic amino acids Leu 390 and Gly 392. The compounds were evaluated for their acute anti-inflammatory activity by the paw and ear edema in the rat model. Karanjin inhibits paw edema and ear edema by 34.13% and 51.13%, respectively, whereas the derivatives inhibited by 45-57 % and 70-76.8%. This study reports a rational approach to synthesize karanjin derivatives with considerable anti-inflammatory properties, both in-vitro and in-vivo.

Disposition, Metabolism and Histone Deacetylase and Acetyltransferase Inhibition Activity of Tetrahydrocurcumin and Other Curcuminoids

Tetrahydrocurcumin (THC), curcumin and calebin-A are curcuminoids found in turmeric (Curcuma longa). Curcuminoids have been established to have a variety of pharmacological activities and are used as natural health supplements. The purpose of this study was to identify the metabolism, excretion, antioxidant, anti-inflammatory and anticancer properties of these curcuminoids and to determine disposition of THC in rats after oral administration. We developed a UHPLC-MS/MS assay for THC in rat serum and urine. THC shows multiple redistribution phases with corresponding increases in urinary excretion rate. In-vitro antioxidant activity, histone deacetylase (HDAC) activity, histone acetyltransferase (HAT) activity and anti-inflammatory inhibitory activity were examined using commercial assay kits. Anticancer activity was determined in Sup-T1 lymphoma cells. Our results indicate THC was poorly absorbed after oral administration and primarily excreted via non-renal routes. All curcuminoids exhibited multiple pharmacological effects in vitro, including potent antioxidant activity as well as inhibition of CYP2C9, CYP3A4 and lipoxygenase activity without affecting the release of TNF-α. Unlike curcumin and calebin-A, THC did not inhibit HDAC1 and PCAF and displayed a weaker growth inhibition activity against Sup-T1 cells. We show evidence for the first time that curcumin and calebin-A inhibit HAT and PCAF, possibly through a Michael-addition mechanism.

Inhibition of lipoxygenase by sesamol corroborates its potential anti-inflammatory activity

Reactive oxygen species, the byproducts of oxygenases reaction, when in excess, promote degenerative diseases like cardiovascular, cancer and arthritis. Sesame lignans- sesamin, sesamolin and the phenolic degradation product of sesamolin, sesamol, are empirically known for their health promoting properties like antioxidant, antimutagenic, antiaging and antiinflammatory activities. In the current study, the effect of sesamol on the inflammatory oxygenase - lipoxygenase (LOX) was investigated. Enzyme kinetics and spectroscopic techniques were used to understand the inhibition mechanism. Sesamol was a potent inhibitor of soy LOX-1. It inhibited soy LOX-1 in a dose dependent manner with IC50 value of 51.84μM and Ki of 4.9μM. Binding studies using circular dichroism and corroborated by surface plasmon resonance, revealed that sesamol does not bind or change the conformation of LOX. Further, sesamol prevented the conversion of inactive LOX (Fe2+) to active LOX (Fe3+) by arresting the oxidation state of iron and prolonging the lag phase by virtue of its ability to scavenge hydroperoxides. Understanding the mechanism of action of such molecules will help in their application and promotion as nutraceuticals.

Synthesis of amino acid conjugates of tetrahydrocurcumin and evaluation of their antibacterial and anti-mutagenic properties

Tetrahydrocurcumin (THC), the hydrogenated and stable form of curcumin, exhibits physiological and pharmacological activities similar to curcumin. A protocol has been developed for the synthesis of novel conjugates of THC with alanine (2a), isoleucine (2b), proline (2c), valine (2d), phenylalanine (2e), glycine (2f) and leucine (2g) in high yields (43-82%). All the derivatives of THC exhibited more potent anti-microbial activity than THC against Bacillus cereus, Staphylococcus aureus, Escherichia coli and Yersinia enterocolitica. The MIC values of the derivatives were 24-37% of those for THC in case of both gram-positive and gram-negative bacteria. Derivatives 2g and 2d exhibited maximum anti-mutagenicity against Salmonella typhimurium TA 98 and TA 1538, respectively at a low concentration of 313 μg/plate, with comparable activity for THC evident only at 3750 μg/plate. These results clearly demonstrated that the conjugation of THC at the phenolic position with amino acids led to significant improvement of its in vitro biological attributes.