Phytochemical Investigation and Biological Activities of Desmodium heterocarpon Extract as Anti-Tyrosinase: Isolation of Natural Compounds, In Vitro and In Silico Study

Tyrosinase is an important enzyme in the biosynthesis of melanin. Many skin-whitening agents that inhibit tyrosinase activity from natural sources have been identified because they are harmless and non-toxic. In this work, 114 samples of 54 Fabaceae plants were assessed for their anti-tyrosinase activity using a dopachrome method. The results found that Desmodium heterocarpon stems and roots demonstrated the highest tyrosinase inhibitory activity at 20 µg/mL (92.50 ± 1.09%), whereas the water extract of Artocarpus lacucha and kojic acid demonstrated 87.41 ± 0.61% and 95.71 ± 0.33%, respectively. Six compounds were isolated from this plant, including genistein (1); hexadecanoic acid (2); salicylic acid (3); β-sitosterol-D-glucoside (4); 2,3-dihydroxybenzoic acid (5); and 2,5-dihydroxybenzoic acid (6). Among them, 2,5-dihydroxybenzoic acid demonstrated a potential effect for tyrosinase inhibition with an IC50 of 57.38 µg/mL, while standards of kojic acid and the water extract of A. lacucha showed 2.46 and 0.15 µg/mL, respectively. 2,3-dihydroxybenzoic acid had a similar structure as 2,5-dihydroxybenzoic acid; however, it was shown to have tyrosinase inhibitory activity, with an IC50 of 128.89 µg/mL. Studies using computer simulations confirmed this reservation. The determination of antimicrobial activities found that 2,5-dihydroxybenzoic acid showed the strongest inhibitory activity against Staphylococcus aureus, with MIC and MBC of 5 and 5 µg/mL, respectively. In addition, it inhibited MRSA, S. epidermidis, Propionibacterium acnes, Escherichia coli, and Pseudomonas aeruginosa, with MIC and MBC of 15–30 and 15–40 µg/mL. It showed potential activities against yeast and filamentous fungi, such as Candida albicans, Microsporum gypseum, Trichophyton rubrum, and T. mentagrophytes, with MIC and MFC of 15 µg/mL. So, 2,5-dihydroxybenzoic acid could inhibit tyrosinase activity and microorganisms that cause skin diseases. Therefore, it can be concluded that this plant has advantageous properties that will be investigated and further developed for possible uses, particularly in the cosmetic and pharmaceutical industries.This study was financially supported by the Graduate School, Prince of Songkla University, the Discipline of Excellence (DOE) in Pharmacy Project, Dissertation Funding for Thesis, Faculty of Pharmaceutical Sciences, Prince of Songkla University and a Postdoctoral Fellowship from Prince of Songkla University, Thailand.Graduate School, Prince of Songkla Universitythe Discipline of Excellence (DOE) in Pharmacy ProjectFaculty of Pharmaceutical Sciences, Prince of Songkla University and a Postdoctoral Fellowship from Prince of Songkla University, Thailan

Antibacterial, antibiofilm, and anti-adhesion activities of Piper betle leaf extract against Avian pathogenic Escherichia coli

Piper betle leaves have traditionally been used to treat many diseases, including bacterial infections. The present studyaimed to investigate the antibacterial, antibiofilm, and anti-adhesion activities of P. betle extract against avian pathogenicEscherichia coli (APEC). The ethanol extract of P. betle leaves demonstrated strong antibacterial activity against clinicalisolates of APEC with MIC and MBC values ranging from 0.5 to 1.0 mg/mL as compared with 1% DMSO, a negative control.Disruption and breakdown of the bacterial cells were detected when the cells were challenged with the extract at 2 × MIC.Bacterial cells treated with the extract demonstrated longer cells without a septum, compared to the control. The extract at1/8, 1/4, and 1/2× MIC significantly inhibited the formation of the bacterial biofilm of all the tested isolates except the iso-late CH10 (P < 0.05) without inhibiting growth. At 1/2 × MIC, 55% of the biofilm inhibition was detected in APEC CH09,a strong biofilm producer. At 32 × MIC, 88% of the inhibition of viable cells embedded in the mature biofilm was detectedin APEC CH09. Reduction in the bacterial adhesion to surfaces was shown when APEC were treated with sub-MICs of theextract as observed by SEM. Hydroxychavicol was found to be the major compound presented in the leaf extract as detectedby GC–MS analysis. The information suggested potential medicinal benefits of P. betle extract to inhibit the growth, biofilm,and adhesion of avian pathogenic E. coli.publishe

Curcumin effect on Acanthamoeba triangularis encystation under nutrient starvation

Curcumin is an active compound derived from turmeric, Curcuma longa, and is known for its benefits to human health. The amoebicidal activity of curcumin against Acanthamoeba triangularis was recently discovered. However, a physiological change of intracellular pathways related to A. triangularis encystation mechanism, including autophagy in the surviving amoeba after curcumin treatment, has never been reported. This study aims to investigate the effect of curcumin on the survival of A. triangularis under nutrient starvation and nutrient-rich condition, as well as to evaluate the A. triangularis encystation and a physiological change of Acanthamoeba autophagy at the mRNA level. In this study, A. triangularis amoebas were treated with a sublethal dose of curcumin under nutrient starvation and nutrient-rich condition and the surviving amoebas was investigated. Cysts formation and vacuolization were examined by microscopy and transcriptional expression of autophagy-related genes and other encystation-related genes were evaluated by real-time PCR. A. triangularis cysts were formed under nutrient starvation. However, in the presence of the autophagy inhibitor, 3-methyladenine (3-MA), the percentage of cysts was significantly reduced. Interestingly, in the presence of curcumin, most of the parasites remained in the trophozoite stage in both the starvation and nutrient-rich condition. In vacuolization analysis, the percentage of amoebas with enlarged vacuole was increased upon starvation. However, the percentage was significantly declined in the presence of curcumin and 3-MA. Molecular analysis of A. triangularis autophagy-related (ATG) genes showed that the mRNA expression of the ATG genes, ATG3, ATG8b, ATG12, ATG16, under the starvation with curcumin was at a basal level along the treatment. The results were similar to those of the curcumin-treated amoebas under a nutrient-rich condition, except AcATG16 which increased later. On the other hand, mRNA expression of encystation-related genes, cellulose synthase and serine proteinase, remained unchanged during the first 18 h, but significantly increased at 24 h post treatment. Curcumin inhibits cyst formation in surviving trophozoites, which may result from its effect on mRNA expression of key Acanthamoeba ATG-related genes. However, further investigation into the mechanism of curcumin in A. triangularis trophozoites arrest and its association with autophagy or other encystation-related pathways is needed to support the future use of curcumin

Anti-Acanthamoeba activity of a semi-synthetic mangostin derivative and its ability in removal of Acanthamoeba triangularis WU19001 on contact lens

Garcinia mangostana L., also known as the mangosteen tree, is a native medicinal plant in Southeast Asia having a wide variety of pharmacologically active compounds, including xanthonoid mangostin. In this study, we examined the pharmacological activities of the selected semi-synthetic mangostin derivative, namely, amoebicidal activity, encystation inhibition, excystation activity, and removal capacity of adhesive Acanthamoeba from the surface of contact lens (CL). Among the three derivatives, C1 exhibited promising anti-Acanthamoeba activity against Acanthamoeba triangularis WU19001 trophozoites and cysts. SEM images displayed morphological changes in Acanthamoeba trophozoites, including the loss of acanthopodia, pore formation in the cell membrane, and membrane damage. In addition, the treated cyst was shrunken and adopted an irregular flat cyst shape. Under a fluorescence microscope, acridine orange and propidium iodide (AO/PI) staining revealed C1 induced condensation of cytoplasm and chromatin with the loss of cell volume in the treated trophozoites, while calcofluor white staining demonstrated the leakage of cell wall in treated cysts, leading to cell death. Interestingly, at the concentration ranges in which C1 showed the anti-Acanthamoeba effects (IC50 values ranging from 0.035–0.056 mg/mL), they were not toxic to Vero cells. C1 displayed the highest inhibitory effect on A. triangularis encystation at 1/16×MIC value (0.004 mg/mL). While C1 demonstrated the excystation activity at 1/128×MIC value with a high rate of 89.47%. Furthermore, C1 exhibited the removal capacity of adhesive Acanthamoeba from the surface of CL comparable with commercial multipurpose solutions (MPSs). Based on the results obtained, C1 may be a promising lead agent to develop a therapeutic for the treatment of Acanthamoeba infections and disinfectant solutions for CL

Targeting Acanthamoeba proteins interaction with flavonoids of Propolis extract by in vitro and in silico studies for promising therapeutic effects

Background: Propolis is a natural resinous mixture produced by bees. It provides beneficial effects on human health in the treatment/management of many diseases. The present study was performed to demonstrate the anti-Acanthamoeba activity of ethanolic extracts of Propolis samples from Iran. The interactions of the compounds and essential proteins of Acanthamoeba were also visualized through docking simulation. Methods: The minimal inhibitory concentrations (MICs) of Propolis extract against Acanthamoeba trophozoites and cysts was determined in vitro. In addition, two-fold dilutions of each of agents were tested for encystment, excystment and adhesion inhibitions. Three major compounds of Propolis extract such as chrysin, tectochrysin and pinocembrin have been selected in molecular docking approach to predict the compounds that might be responsible for encystment, excystment and adhesion inhibitions of A. castellanii. Furthermore, to confirm the docking results, molecular dynamics (MD) simulations were also carried out for the most promising two ligand-pocket complexes from docking studies. Results: The minimal inhibitory concentrations (MICs) 62.5 and 125 µg/mL of the most active Propolis extract were assessed in trophozoites stage of Acanthamoeba castellanii ATCC30010 and ATCC50739, respectively. At concentrations lower than their MICs values (1/16 MIC), Propolis extract revealed inhibition of encystation. However, at 1/2 MIC, it showed a potential inhibition of excystation and anti-adhesion. The molecular docking and dynamic simulation revealed the potential capability of Pinocembrin to form hydrogen bonds with A. castellanii Sir2 family protein (AcSir2), an encystation protein of high relevance for this process in Acanthamoeba. Conclusions: The results provided a candidate for the development of therapeutic drugs against Acanthamoeba infection. In vivo experiments and clinical trials are necessary to support this claim

Antifungal metabolites from marine-derived Streptomyces sp. AMA49 against Pyricularia oryzae

Marine-derived actinobacteria are considered as potential sources of bioactive metabolites including antifungal substances. Fifteen out of 155 marine-derived actinobacteria exhibited strong antifungal activity against the rice blast fungus Pyricularia oryzae. Their extracts were further determined for minimum inhibitory concentrations (MIC) and minimum fungicidal concentrations (MFC). Ethyl acetate extract from the strain AMA49 and its subfraction AMA49F1 strongly inhibited hyphal growth of various P. oryzae strains with MICs (8 to 16µg/ml) and MFCs (16 to 128µg/ml) comparable to propiconazole. Both extracts destroyed fungal membrane and organelles, completely inhibited conidial germination, appressorium formation, and were non-toxic to Galleria mellonella. High performance liquid chromatography/mass spectrometry identified oligomycin A and its derivatives as the active components of AMA49F1 besides several diketopiperazines. AMA49 was identified as a Streptomyces sp. based on morphological characteristics and 16S rDNA sequence analysis. The results suggest that the Streptomyces sp. strain AMA49 is a potential biocontrol agent against rice blast pathogen P. oryzae. This is the first report on the inhibitory effect of the marine-derived Streptomyces extract containing oligomycin A and its derivatives on mycelial growth, conidial germination and appressorium formation of P. oryzae

Conserved Candidate Antigens and Nanoparticles to Develop Vaccine against <i>Giardia intestinalis</i>

Giardia intestinalis (Giardia lambia, Giardia duodenalis) infections in humans may be asymptomatic or symptomatic and associated with diarrhea (without blood), abdominal cramps, bloating, flatulence, and weight loss. The protozoan Giardia is the third most common cause of diarrhea and death in children under five, preceded only by rotavirus and by Cryptosporidium parvum and C. hominis infections. Antimicrobial drugs, particularly 5-nitroimidazole (5-NIs), are used to treat giardiasis in humans. Immunologically naive or immunocompromised host are more vulnerable to Giardia infection, whereas a degree of resistance to this protozoan is present in humans living in endemic areas. This suggests that vaccination may be a potential and appropriate means to control this parasitic disease outbreak and protect the human population. This review discusses Giardia antigens related to vaccine development. Additionally, based on the latest development of nanoparticle technology, a combination of methods for future research and development is proposed for the design of the next generation of powerful immunogens and an effective vaccine against Giardia

Phytochemical, anti-Acanthamoeba, and anti-adhesion properties of Garcinia mangostana flower as preventive contact lens solution

Acanthamoeba keratitis infection extends due to the growing number of contact lens users. Indigenous plants including Garcinia mangostana play a vital role in human health and well being. Many species of this plant have been reported with myriads of potent medicinal properties. However, the aims of this study were, for the first time, to isolate compounds from the flower of G. mangostana and to test their anti-Acanthamoeba and antiadhesion activity against Acanthamoeba triangularis. Powdered flowers of G. mangostana were extracted and chromatographed on a silica gel column. The structures of the compounds were established with the aid of 1 H NMR. More so, the anti-Acanthamoeba and anti-adhesion properties were tested on a 96-well polystyrene microtiter plate and soft contact lenses. Scanning electron microscope (SEM) was used to determine the features of A. triangularis on contact lenses. Eight pure compounds were obtained, namely 9-hydroxycalabaxanthone, tovophillin A, garcinone E, garcinone B, α-mangostin, gartinin, 8-deoxygartinin and γ-mangostin. The extract and pure compounds exhibited anti-Acanthamoeba activity with MIC values in the range of 0.25–1 mg/mL. In addition, the extract and α-mangostin displayed significant activity against the adhesion of A. triangularis trophozoites both in polystyrene plate and in contact lenses at 0.5 × MIC (0.25 mg/mL). Furthermore, α-mangostin has the potential to remove A. triangularis adhesion in contact lenses similar to a commercial multipurpose solution (MPS). SEM study confirmed that crude extract and α-mangostin are effective as solutions for contact lenses, which removed A. triangularis trophozoites within 24 h. Alpha-mangostin was non-toxic to Vero cells at a concentration below 39 μM in 24 h. Crude extract of G. mangostana flower and its α-mangostin serve as candidate compounds in the treatment of Acanthamoeba infection or as lens care solution, since they can be used as a source of natural products against Acanthamoeba and virulence factor associated with the adhesion of A. triangularis

Targeting Acanthamoeba proteins interaction with flavonoids of Propolis extract by in vitro and in silico studies for promising therapeutic effects [version 2; peer review: 2 approved]

Background: Propolis is a natural resinous mixture produced by bees. It provides beneficial effects on human health in the treatment/management of many diseases. The present study was performed to demonstrate the anti-Acanthamoeba activity of ethanolic extracts of Propolis samples from Iran. The interactions of the compounds and essential proteins of Acanthamoeba were also visualized through docking simulation. Methods: The minimal inhibitory concentrations (MICs) of Propolis extract against Acanthamoeba trophozoites and cysts was determined in vitro. In addition, two-fold dilutions of each of agents were tested for encystment, excystment and adhesion inhibitions. Three major compounds of Propolis extract such as chrysin, tectochrysin and pinocembrin have been selected in molecular docking approach to predict the compounds that might be responsible for encystment, excystment and adhesion inhibitions of A. castellanii. Furthermore, to confirm the docking results, molecular dynamics (MD) simulations were also carried out for the most promising two ligand-pocket complexes from docking studies. Results: The minimal inhibitory concentrations (MICs) 62.5 and 125 µg/mL of the most active Propolis extract were assessed in trophozoites stage of Acanthamoeba castellanii ATCC30010 and ATCC50739, respectively. At concentrations lower than their MICs values (1/16 MIC), Propolis extract revealed inhibition of encystation. However, at 1/2 MIC, it showed a potential inhibition of excystation and anti-adhesion. The molecular docking and dynamic simulation revealed the potential capability of Pinocembrin to form hydrogen bonds with A. castellanii Sir2 family protein (AcSir2), an encystation protein of high relevance for this process in Acanthamoeba. Conclusions: The results provided a candidate for the development of therapeutic drugs against Acanthamoeba infection. In vivo experiments and clinical trials are necessary to support this claim