As part of our effort to develop potential tyrosinase inhibitors, we have conjugated the well-known tyrosinase inhibitor kojic acid (KA) with several phenolic natural products such as umbelliferone, ...sesamol, thymol, carvacrol, eugenol, isoeugenol, vanillin, isovanillin, and apocynin that some reports have shown their activity on tyrosinase enzyme. The designed compounds were synthesized using click reaction and 1,2,3-triazole formation. All compound showed potent anti-tyrosinase activity significantly higher than KA. The best activities were observed with apocynin and 4-coumarinol analogs (10c and 16c) displaying IC50 values of 0.03 and 0.02 μM, respectively. The potency of 16c was >460-times more than that of KA. Cell-based assays against B16F10 and HFF cells revealed that the representative compounds can efficiently suppress the melanogenesis without significant toxicity on cells.
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•A series of kojic acid (KA)–natural product conjugates were prepared via click reaction.•All compounds 2c-16c were highly potent tyrosinase inhibitors (IC50s ≤ 3.75 μM).•Apocynin and 4-coumarinol derivatives (10c and 16c) were the most potent compounds.•The 4-coumarinol analog (16c) was >460-fold more potent than KA.•Certainly, 16c can suppress melanogenesis without significant toxicity on B16F10 cells.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Molecules that alter the normal dynamics of microtubule assembly and disassembly include many anticancer drugs in clinical use. So far all such therapeutics target β-tubulin, and structural biology ...has explained the basis of their action and permitted design of new drugs. However, by shifting the profile of β-tubulin isoforms, cancer cells become resistant to treatment. Compounds that bind to α-tubulin are less well characterized and unexploited. The natural product pironetin is known to bind to α-tubulin and is a potent inhibitor of microtubule polymerization. Previous reports had identified that pironetin reacts with lysine-352 residue however analogues designed on this model had much lower potency, which was difficult to explain, hindering further development. We report crystallographic and mass spectrometric data that reveal that pironetin forms a covalent bond to cysteine-316 in α-tubulin via a Michael addition reaction. These data provide a basis for the rational design of α-tubulin targeting chemotherapeutics.
Eight examples of biosynthetic pathways wherein a natural enzyme has been identified and claimed to function as a catalyst for the 4 + 2 cycloaddition reaction, namely, Diels–Alderases, are briefly ...reviewed. These are discussed in the context of the mechanistic challenges associated with the technical difficulty of proving that the net formal 4 + 2 cycloaddition under study indeed proceeds through a synchronous mechanism and that the putative biosynthetic enzyme deploys the pericyclic transition state required for a Diels–Alder cycloaddition reaction.
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One new α-pyrone (nocapyrone R (1)), and three known γ-pyrones (nocapyrones B, H and L (2-4)) were isolated from the culture extract of a Nocardiopsis strain collected from marine sediment. ...Structures of these compounds were determined on the basis of spectroscopic data including NMR and MS. γ-Pyrones 2-4 were found to induce adiponectin production in murine ST-13 preadipocyte cells but the α-pyrone 1 had no activity. The absolute configuration of the anteiso-methyl branching in 4 was determined by HPLC comparison of a degraded product of 4 with standard samples as a 2:3 enantiomeric mixture of (R)- and (S)-isomers.
Natural dibenzo-α-pyrones are an important group of metabolites derived from fungi, mycobionts, plants and animal feces. They exhibit a variety of biological activities such as toxicity on human and ...animals, phytotoxicity as well as cytotoxic, antioxidant, antiallergic, antimicrobial, antinematodal, and acetylcholinesterase inhibitory properties. Dibenzo-α-pyrones are biosynthesized via the polyketide pathway in microorganisms or metabolized from plant-derived ellagitannins and ellagic acid by intestinal bacteria. At least 53 dibenzo-α-pyrones have been reported in the past few decades. This mini-review aims to briefly summarize the occurrence, biosynthesis, biotransformation, as well as their biological activities and functions. Some considerations related to synthesis, production and applications of dibenzo-α-pyrones are also discussed.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The neglected tropical diseases Chagas disease and leishmaniasis affect together more than 20 million people living mainly in developing countries. The mainstay of treatment is chemotherapy, however ...the drugs of choice, which include benznidazole and miltefosine, are toxic and have numerous side effects. Safe and effective therapies are urgently needed. Marine alpha-pyrones have been previously identified as scaffolds with potential antiprotozoan activities. In this work, using a phenotypic screen, twenty-seven examples of 3-substituted 4-hydroxy-6-methyl alpha-pyrones were synthesized and their antiparasitic efficacy evaluated against Leishmania (L.) infantum and Trypanosoma cruzi in order to evaluate structure-activity relationships within the series. The mechanism of action and the in vivo efficacy of the most selective compound against T. cruzi were evaluated using different techniques. In vitro data indicated that compounds 8, 15, 25, 26 and 28 presented IC50 values in the range between 13 and 54 μM against L. infantum intracellular amastigotes. Among them, hexanoyl substituted pyrone 8 was the most selective and potent, with a Selectivity Index (SI) > 14. Fifteen of the alpha-pyrones were effective against T. cruzi trypomastigotes, with 3-undecanoyl (11) and 3-tetradecanoyl (12) substituted pyrones being the most potent against trypomastigotes, with IC50 values of 1 and 2 μM, respectively, and SI higher than 70. Using flow cytometry and fluorescent-based assays, pyrone 12 was found to induce hyperpolarization of the mitochondrial membrane potential of T. cruzi, without affecting plasma membrane permeability. An experimental acute phase-murine model, demonstrated that in vivo dosing of 12 (30 mg/kg/day; 5 days), had no efficacy at the first parasitemia onset of T. cruzi, but reduced the second onset by 55% (p < 0.05), suggesting a delayed action in BALB/c mice. Additionally, a histopathology study demonstrated no toxic effects to the treated mice. The finding that several 3-substituted alpha-pyrones have in vitro efficacy against both L. infantum and T. cruzi, and that one analogue exhibited moderate and non-toxic in vivo efficacy against T. cruzi is encouraging, and suggests that this compound class should be explored as long-term treatments in experimental Chagas disease.
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•The SAR of 3-substituted 4-hydroxy-6-methyl-2-pyrone derivatives were explored.•Several derivatives exhibited in vitro efficacy against L. infantum and T. cruzi.•One derivative exhibited moderate, non-toxic in vivo efficacy against T. cruzi.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Human lactate dehydrogenase A (LDHA) plays a critical role in the glycolytic process, making the enzyme an ideal of anti-cancer drug target. Herein, we report the discovery of novel potent LDHA ...inhibitors by screening an in-house library. The hit-to-lead modification enabled us to identify compound 24c, which inhibited LDHA activity with an EC50 value of 90 nM, and reduced MiaPaCa-2 cancer cell proliferation with an IC50 value of 2.1 μM. In line with the in vitro anticancer activity, 24c suppressed the tumor growth at a dose of 10 mg/kg in a MiaPaCa-2 cells xenograft model, but with little effect to the mice weight. Moreover, 24c strongly inhibited MiaPaCa-2 cell colonies formation, induced MiaPaCa-2 cell apoptosis, and arrested MiaPaCa-2 cell cycle at G2 phase. In addition, the mitochondrial bioenergetics analysis suggested that 24c could reprogram cancer cell metabolic pathways from glycolysis to oxidation phosphorylation, which verified by decreasing the extracellular acidification rates and lactate formation, and increasing oxygen consumption rate in cancer cell. All these results indicate 24c is a promising metabolic modulator for the anticancer drug development.
Compound 24c exhibited a potent biochemical potency, and in vitro and in vivo anticancer activity. Display omitted
•Compound 24c inhibited LDHA with an EC50 value of 90 nM.•Compound 24c reduced MiaPaCa-2 cell proliferation with an IC50 value of 2.1 μM.•Compound 24c suppressed tumor growth in a xenograft model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•Two series of novel kojic acid analogues were synthesized.•All newly synthesized compounds were screened for tyrosinase inhibitory activity.•Most of the prepared compounds exhibited ...significant inhibitory activity of tyrosinase in vitro.•The structure-activity relationship was discussed.
Two series of novel kojic acid analogues (4a–j) and (5a–d) were designed and synthesized, and their mushroom tyrosinase inhibitory activities was evaluated. The result indicated that all the synthesized derivatives exhibited excellent tyrosinase inhibitory properties having IC50 values in the range of 1.35±2.15–17.50±2.75μM, whereas standard inhibitor kojic acid have IC50 values 20.00±1.08μM. Specifically, 5-phenyl-3-5-hydroxy-4-pyrone-2-yl-methylmercap-to-4-(2,4-dihydroxyl-benzylamino)-1,2,4-triazole (4f) exhibited the most potent tyrosinase inhibitory activity with IC50 value of 1.35±2.15μM. The kinetic studies of the compound (4f) demonstrated that the inhibitory effects of the compound on the tyrosinase were belonging to competitive inhibitors. Meanwhile, the structure-activity relationship was discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Successful activation of the pyranonigrin biosynthetic gene cluster and gene knockout in Aspergillus niger plus in vivo and in vitro assays led to isolation of six new products, including a spiro ...cyclobutane-containing dimeric compound, which served as the basis for the proposed comprehensive pyranonigrin biosynthetic pathway. Two redox enzymes are key to forming the characteristic fused γ-pyrone core, and a protease homologue performs the exo-methylene formation.
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