In Vitro and In Silico Studies of Two 1,4-Naphthoquinones and Their Topical Formulation in Bigels.

BACKGROUND: 1,4-Naphthoquinones (1,4-NQs) are secondary plant metabolites with numerous biological activities. 1,4-NQs display low water solubility and poor bioavailability. Bigels are a new technology with great potential, which are designated as drug delivery systems. Biphasic bigels consisting of solid and liquid components represent suitable formulations improving diffusion and bioavailability of NQs into the skin. OBJECTIVE: We evaluated the in silico and in vitro activity of 5,8-dihydroxy-1,4-naphthoquinone (M1) and 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (M2) on elastase and assessed their cytotoxicity towards COLO38 melanoma cells. The 1,4-NQs were loaded into bigels for topical application. METHODS: Molecular docking was performed, and cytotoxicity was evaluated on COLO38 cells using the resazurin assay. M1 and M2 were separately incorporated into bigels consisting of hydrogel organogel with sweet almond oil as the non-polar solvent and span 65 as an organogelator. Their rheological behavior and microscopic properties were characterized. The diffusion kinetics and permeation of 1,4-NQs from bigels were studied by a paddle-over-extraction cell and a "Franz cell" in vitro permeation model. RESULTS: Molecular docking data predicted high interactions between elastase and ligands. Hydrogen bonds with LYS233 were observed for M1, M2, and phosphoramidon (positive control). The average binding energies were -8.5 and -9.7 kcal/mol for M1 and M2 and -12.6 kcal/mol for phosphoramidon. M1 and M2 inhibited the elastase activity by 58.9 and 56.6%, respectively. M1 and M2 were cytotoxic towards COLO38 cells (IC50 value: 2.6 and 9.8 µM). The M1 release from bigels was faster and more efficient than that of M2. CONCLUSION: M1 and M2 are promising for skin disease treatment. Biphasic organogel-hydrogel bigels are efficient and safe formulations to overcome their low bioavailability.

Evaluation of in vitro biological activities: antioxidant; anti-inflammatory; anti-cholinesterase; anti- xanthine oxidase, anti-superoxyde dismutase, anti-α-glucosidase and cytotoxic of 19 bioflavonoids.

Pure compounds belonging to phenolic family were studied for their biological potential such as 5,8-dihydroxy-1,4-naphthoquinone (M1), rutin hydrate (M2), 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (M3), taxifolin (M4), myricetin (M5), plumbagin (M6), silibinin (M7), dihydromyricetin (M8), shikonin (M9), quercetin 3-ß-D-glucoside (M10), (±)-taxifolin hydrate (M11), cardamonin (M12),(-)-epicatechin (M13), 9-chloro-10-hydroxy-anthracene-1,4-dione (M14), 9-chloro-10-hydroxy-2,3-dimethyl-anthracene-1,4-dione (M15), 2-chloro-3-(2-hydroxy-5-methylanilino)-1,4-naphthoquinone (M16), 2-chloro-3-(4-hydroxy-phenylamino)-(1,4) naphthoquinone (M17), 2-chloro-3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-(1,4)-naphtoquinone (M18), and myricitrin dihydrate (M19). These molecules were chosen based on two reasons; the limited or total absence of their exploitation in several studied activities and the use of other tests for the same activity. The evaluation of the in vitro anti-acetyl-cholinesterase (AChE), anti-5-lipoxygenase (5-LOX), anti-xanthine oxidase (XOD), anti-alpha glucosidase, anti-superoxide dismutase (SOD), anti-oxidant (DPPH (1, 1-diphenyl-2-picrylhydrazyl) and ABTS (2, 2- azinobis-3-ethylbenzothiazoline-6-sulphonate)), and anticancer activities of mentioned 19 molecules was explored during this work. M3, M14, M15, M16, M17, M18, M19 were exploited for the first time for such purposes. Tested compounds were shown to have interesting radical scavenging abilities against DPPH radicals, and the highest molecules among them were M19 and M5 (IC50 = 12.0 and 15.5 µM, respectively), and M4, M19 and M2 against ABTS (IC50= 1.9, 4.3 and 4.3 µM, respectively). Moreover, the majority of products showed very important cytotoxic activity since IC50 values were ranging between (IC50= 0.2 µM (M1) and 79 µM (M8)) against HCT116 cell line, and values of IC50= 0.2 µM for M1 against MCF7 cell line. All new molecules (non studied before) were shown to have great cytotoxic effect against both cancer cell lines.Furthermore, molecule M5 was shown to have anti-inflammatory potential via the inhibition of 5-LOX enzyme (65% at 100 µM). In addition, M19 showed important anti XOD activity with 47% of inhibition at 100 µM. Also, it has been found that compound M3 had the best anti alpha glucosidase activity with 43.8 % of inhibition at 100 µM, the highest anti-AChE effect (IC50= 14.5 µM), and the best effect towards SOD (IC50= 10.0 µM).  A structure-activity relationship study was also performed.

The antioxidant 2,3-dichloro,5,8-dihydroxy,1,4-naphthoquinone inhibits acetyl-cholinesterase activity and amyloid ß42 aggregation: A dual target therapeutic candidate compound for the treatment of Alzheimer's disease.

Alzheimer's disease is characterized by amyloid ß aggregation and cholinergic neurodegeneration. In the present study, pure DDN (2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone) was examined, for the first time, for its dual potential as inhibitor of acetylcholinesterase (AChE) and Aß42 aggregation. Such investigation was encouraged by the in vitro high antioxidant potential of DDN. Indeed, it revealed interesting antioxidant activity with IC50 values of 9.8 and 4.3 µM for ABTS and reducing power, respectively. The ability of DDN to counteract Aß42 aggregation was evaluated by thioflavine-T assay. Strong inhibition of Aß42 aggregation of more than 90% at 25 µM was measured. Moreover, results showed that DDN inhibited AChE (IC50 = 14.5 µM). To better understand the interactions between DDN and AChE, molecular docking was performed. Obtained data predicted a high interaction characterized by hydrogen bonding at TYR337 as for galanthamine (positive control). Several residues involved in AChE hydrophobic interactions were similarly implicated in binding of this domain to DDN (ASP74, THR83, and TYR124). All these data would be useless if DDN could not pass the blood-brain barrier. So, DDN was loaded into alginate microspheres to enhance its stability and bioavailability. Thereafter, drug release profiles were assessed using immersion cell apparatus.