Anti-melanogenesis potential of a new series of Morita-Baylis-Hillman adducts in B16F10 melanoma cell line.

Melanin is a natural polymer pigment which provides skin photoprotection against ultraviolet radiation. An excessive synthesis of melanin leads to hyperpigmentation disorders. Tyrosinase catalyzes the rate limiting steps on melanogenesis. Therefore, tyrosinase inhibitors have potential applications in medicine and cosmetic fields. We carried out herein the screening of a family of cyclic Morita-Baylis-Hillman adducts (MBH) to find out their effects on tyrosinase activity and on melanogenesis in murine melanoma B16F10 cell line. Kinetic analysis of tyrosinase inhibition showed that compounds 1a (2-hydroxymethyl) cyclohex-2-enone) and 3f (diethyl (1-(6-oxocyclohex-1-en-1-yl) ethyl-phosphonate) were competitive inhibitors, whereas the compound 2b (6-oxocyclohex-1-en-1-yl) ethyl acetate) was a non-competitive one. Additionally we have found that (1a, 2b and 3f) compounds had a strong melanogenesis inhibition effect in isobutylmethylxanthine (IBMX)-treated murine melanoma B16F10 cells when tested at low and non cytotoxic dose (10-50 µM), by attenuating the melanin production, intracellular tyrosinase activity and tyrosinase expression. Thus, we suggest that these compounds could be used as effective skin-whitening agents.

Safety assessment of fish oil green extraction and in vivo acute toxicity evaluation.

Sardine co-products can represent an interesting source of bioactive compounds, such as polyunsaturated fatty acids and in particular omega-3. This study aimed to investigate extraction of oil from sardine co-products by enzymatic hydrolysis using two proteases: commercial Alcalase and protease Bb from a local fungal strain (P2) of Beauveria bassiana, which overproduces proteases. Despite a higher degree of hydrolysis (41.34%) than Alcalase (24.28%), protease Bb allowed the extraction of approximately the same oil content. Resulting oil from both processes had the same fatty acid profile. Interestingly, the all-produced oil displayed an attractive w6/w3 ratio, an indicator of nutritional quality, of the order of 0.16. The safety of the generated oils was also assessed by treating two groups of Wistar rats with the fish oil administered by oral gavage at the doses (30 mg/kg and 300 mg/kg body weight) for 14 days using olive oil as a vehicle. Compared to controls used, both treated groups showed no statistically significant differences. Consequently, the acute oral toxicity evaluated by hematological, biochemical, and histological studies showed the safety of the oil generated using B. bassiana protease.

Purification and characterization of latent polyphenol oxidase from truffles (Terfezia arenaria).

The polyphenol oxidase was extracted and purified from truffles (Terfezia arenaria) and it exhibited a molecular weight of 67 kDa. The truffle PPO was able to oxidize monophenolic, o-diphenolic and triphenolic substrates. Thus, the enzyme seems to be stable under wide range of pH and temperature. Best catalytic efficiency was observed for catechol as substrate (Kcat/km; 674.2 S-1 mM-1).The effect of detergents, chaotropic agents, metal ions and eleven different inhibitors on relative activity of Truffles PPO was also investigated. A latent form of enzyme was observed and its activity was stimulated using 4 mM of SDS. Likewise, the type of inhibition and the values of KI and IC50 were reported for L-cysteine, Sodium fluoride, sodium metabisulfite and kojic acid. Besides, the effect of four concentrations of kojic acid(0.05.,0.1.,0.2 and 0.3 mM) on thermal inactivation of PPO was performed in temperature range " 60-75° C". The use of Kojic acid increase the rate of inactivation process and disrupt enzymatic activity. Moreover, the combined effect of temperature and kojic acid prevent from enzymatic browning reaction and maintain high antioxidant activities including ABTS scavenging activity, FRAP, and total phenolic contents.

Purification and characterization of catechol oxidase from Tadela (Phoenix dactylifera L.) date fruit.

Catechol oxidase (PPO) was extracted and purified from Tadela (Phoenix dactylifera L.) date fruit, by a procedure that included (NH4)2SO4 precipitation followed by dialysis, Q-Sepharose bb ion-exchange chromatography and HPLC gel filtration chromatography. Some of its biochemical characteristics were studied. The purification rate and the yield were 80% and 20%, respectively. The Tadela date fruit catechol oxidase exhibited a molecular weight of 90 kDa using SDS-PAGE. The catechol oxidase showed only o­diphenolase and triphenolase activities while no monophenolase activity was detected. A better affinity was observed using catechol as substrate (Km = 35 mM) with thus, a higher Vmax/Km ratio (80 U/mM·mL). This enzyme is thermostable in the temperature range (30-60 °C) with optimum activity in acidic range of pH. Four inhibitors were used for the control of enzymatic browning, of which sodium metabisulfite was the most potent (IC50 = 0, 11 mM). The values of KI and mechanism of inhibition were also determined. No significant change on enzyme activity was noticed in the presence of metal ion and detergents. Therefore, thermal inactivation was studied in the temperature range between 60 and 80 °C using catechol as substrate. Their kinetic (K, D, t1/2, Zt, Ea) and thermodynamic (ΔH, ΔG and ΔS) parameters were also estimated.

Aryl Butenes Active against K562 Cells and Lacking Tyrosinase Inhibitory Activity as New Leads in the Treatment of Leukemia.

BACKGROUND & OBJECTIVE: The inhibitory effects of four series of aryl butene derivatives, active against breast cancer, on the monophenolase activity of tyrosinase, in melanin-free ink from Sepia officinalis, have been studied. Hydroxytamoxifen 1, ferrociphenol 17 and several aryl butene analogs have shown strong antiproliferative activity on hormone-dependent and hormone-independent breast cancer cells and were evaluated in leukemia K562 cell proliferation. Their potential to induce skin depigmentation by evaluating their anti-tyrosinase activity was also estimated. In order to better rationalize the tyrosinase inhibitory action and the binding mode of the compounds, docking studies were carried out. CONCLUSION: Hydroxytamoxifen and some aryl butenes showed strong antiproliferative effects against K562 cells at 1 µM without showing tyrosinase inhibition. If phenolic compounds 16 and 17 showed the best antiproliferative activity on K562, Hydroxytamoxifen and compounds 5, 10, 20 and 21 have been identified as candidates for further development against chronic myeloid leukemia (CML), and are predicted to not induce depigmentation of the skin, a side effect encountered with imatinib, conventionally used for the treatment of CML.