Background Asphodelus microcarpus belongs to the family Liliaceae that include several medicinal plants. In the traditional medicine plants of the genus Asphodelus are used to treat skin disorders such as ectodermal parasites, psoriasis, microbial infection and for lightening freckles. In order to find novel skin depigmenting agents, the present work was carry out to evaluate antioxidant activity and tyrosinase inhibitory potential of leaves, flowers and tubers extracts of A. microcarpus. The phytochemical composition of the active extract was also evaluated.MethodsThree different extracts (water, methanol and ethanol) from leaves, flowers and tubers of A. microcarpus were evaluated for their inhibitory effect on tyrosinase activity using l-3,4-dihydroxyphenylalanine (l-DOPA) as substrate. Inhibition of cellular tyrosinase activity and melanin production was also investigated in melanoma B16F10 cells. Antioxidant activity, total phenolic and flavonoids contents were determined using standard in vitro methods. HPLC-DAD-MS was used to identify phenolic profile of the active extract.ResultsThe results showed that all extracts have a direct inhibitory anti-tyrosinase activity, with ethanolic extract from flowers (FEE) exhibiting the stronger effect. Kinetic analysis revealed that FEE acts as an uncompetitive inhibitor with a Ki value of 0.19 mg/mL. The same effect was observed in murine melanoma B16F10 cells. Cellular tyrosinase activity as well as melanin content were reduced in FEE-treated cells. The results were comparable to that of the standard tyrosinase inhibitor (kojic acid). Furthermore, the same extract showed the highest antioxidant activity and an elevated levels of total phenolics and flavonoid content. Eleven phenolic components were identified as chlorogenic acid, luteolin derivates, naringenin and apigenin.ConclusionsOur findings showed that FEE from A. microcarpus inhibits tyrosinase and exerted antimelanogenesis effect in B16F10 cells. This extract also showed the highest scavenging activity, which could be mainly attributed to its high levels of total polyphenols and flavonoids. These results suggest that A. microcarpus has a great potential as sources of bioactive compounds which could be used as depigmenting agents in skin disorders.

Alzheimer’s disease (AD) is a neurodegenerative disorder representing the leading cause of dementia and is affecting nearly 44 million people worldwide. AD is characterized by a progressive decline in acetylcholine levels in the cholinergic systems, which results in severe memory loss and cognitive impairments. Expression levels and activity of butyrylcholinesterase (BChE) enzyme has been noted to increase significantly in the late stages of AD, thus making it a viable drug target. A series of hydroxylated 2-phenylbenzofurans compounds were designed, synthesized and their inhibitory activities toward acetylcholinesterase (AChE) and BChE enzymes were evaluated. Two compounds (15 and 17) displayed higher inhibitory activity towards BChE with IC50 values of 6.23 μM and 3.57 μM, and a good antioxidant activity with EC50 values 14.9 μM and 16.7 μM, respectively. The same compounds further exhibited selective inhibitory activity against BChE over AChE. Computational studies were used to compare protein-binding pockets and evaluate the interaction fingerprints of the compound. Molecular simulations showed a conserved protein residue interaction network between the compounds, resulting in similar interaction energy values. Thus, combination of biochemical and computational approaches could represent rational guidelines for further structural modification of these hydroxy-benzofuran derivatives as future drugs for treatment of AD.

The aim of the present study was to evaluate antioxidant, antimicrobial, anti-HIV, and cholinesterase inhibitory activities of aqueous and alcoholic extracts from leaves, stems, and flowers of Euphorbia characias. The extracts showed a high antioxidant activity and were a good source of total polyphenols and flavonoids. Ethanolic extracts from leaves and flowers displayed the highest inhibitory activity against acetylcholinesterase and butyrylcholinesterase, showing potential properties against Alzheimer's disease. Antimicrobial assay showed that leaves and flowers extracts were active against all Gram-positive bacteria tested. The ethanolic leaves extract appeared to have the strongest antibacterial activity against Bacillus cereus with MIC value of 312.5 μg/mL followed by Listeria monocytogenes and Staphylococcus aureus that also exhibited good sensitivity with MIC values of 1250 μg/mL. Moreover, all the extracts possessed anti-HIV activity. The ethanolic flower extract was the most potent inhibitor of HIV-1 RT DNA polymerase RNA-dependent and Ribonuclease H with IC50 values of 0.26 and 0.33 μg/mL, respectively. The LC-DAD metabolic profile showed that ethanolic leaves extract contains high levels of quercetin derivatives. This study suggests that Euphorbia characias extracts represent a good source of natural bioactive compounds which could be useful for pharmaceutical application as well as in food system for the prevention of the growth of food-borne bacteria and to extend the shelf-life of processed foods.

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Antibiotic resistance is one of the main public health concerns of this century. This resistance is also associated with oxidative stress, which could contribute to the selection of resistant bacterial strains. Bearing this in mind, and considering that flavonoid compounds are well known for displaying both activities, we investigated a series of hydroxy-3-arylcoumarins with structural features of flavonoids for their antibacterial activity against different bacterial strains. Active compounds showed selectivity against the studied Gram-positive bacteria compared to Gram-negative bacteria. 5,7-Dihydroxy-3-phenylcoumarin (compound 8) displayed the best antibacterial activity against Staphylococcus aureus and Bacillus cereus with minimum inhibitory concentrations (MICs) of 11 g/mL, followed by Staphylococcus aureus (MRSA strain) and Listeria monocytogenes with MICs of 22 and 44 g/mL, respectively. Moreover, molecular docking studies performed on the most active compounds against Staphylococcus aureus tyrosyl-tRNA synthetase and topoisomerase II DNA gyrase revealed the potential binding mode of the ligands to the site of the appropriate targets. Preliminary structure–activity relationship studies showed that the antibacterial activity can be modulated by the presence of the 3-phenyl ring and by the position of the hydroxyl groups at the coumarin scaffold.

Tyrosinase is a well-known key enzyme in melanin biosynthesis and its inhibitors have become increasingly important because of their potential use as hypopigmenting agents. In the present study, the anti-melanogenic effect of aqueous and ethanolic extracts from Euphorbia characias leaves, stems, and flowers in cell-free and cellular systems was examined. All the extracts showed inhibitory effects against mushroom tyrosinase with leaf extracts exhibiting the lowest IC50 values of 24 and 97 µg/mL for aqueous and ethanolic extracts respectively. Enzyme kinetic analysis indicated that leaf aqueous extract acts as a mixed type inhibitor, while ethanolic extract shows a competitive inhibition effect on mushroom tyrosinase using L-DOPA as substrate. In addition, the inhibitory effect of leaf extracts on tyrosinase activity and melanin production was examined in murine melanoma B16F10 cells. Cellular tyrosinase activity as well as levels of melanin synthesis are reduced in a dose-dependent manner by extracts in cells treated with α-melanocyte stimulating hormone (α-MSH). The effects are comparable, and sometimes even better, than that of kojic acid, a well known tyrosinase inhibitor used for reference. All these results suggest that E. characias could be a great source of the natural inhibitors from tyrosinase and has the potential to be used as a whitening agent in therapeutic fields.

In this manuscript we report the synthesis, pharmacological evaluation and docking studies of a selected series of 3-aryl and 3-heteroarylcoumarins with the aim of finding structural features for the tyrosinase inhibitory activity. The synthesized compounds were evaluated as mushroom tyrosinase inhibitors. Compound 12b showed the lowest IC50 (0.19 μM) of the series, being approximately 100 times more active than kojic acid, used as a reference compound. The kinetic studies of tyrosinase inhibition revealed that 12b acts as a competitive inhibitor of mushroom tyrosinase with l-DOPA as the substrate. Furthermore, the absence of cytotoxicity in B16F10 melanoma cells was determined for this compound. The antioxidant profile of all the derivatives was evaluated by measuring radical scavenging capacity (ABTS and DPPH assays). Docking experiments were carried out on mushroom tyrosinase structures to better understand the structure-activity relationship

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