Synergistic effect of potential alpha-amylase inhibitors from Egyptian propolis with acarbose using in silico and in vitro combination analysis.

BACKGROUND: Type 2 Diabetes mellitus (DM) is an affliction impacting the quality of life of millions of people worldwide. An approach used in the management of Type 2 DM involves the use of the carbohydrate-hydrolyzing enzyme inhibitor, acarbose. Although acarbose has long been the go-to drug in this key approach, it has become apparent that its side effects negatively impact patient adherence and subsequently, therapeutic outcomes. Similar to acarbose in its mechanism of action, bee propolis, a unique natural adhesive biomass consisting of biologically active metabolites, has been found to have antidiabetic potential through its inhibition of α-amylase. To minimize the need for ultimately novel agents while simultaneously aiming to decrease the side effects of acarbose and enhance its efficacy, combination drug therapy has become a promising pharmacotherapeutic strategy and a focal point of this study. METHODS: Computer-aided molecular docking and molecular dynamics (MD) simulations accompanied by in vitro testing were used to mine novel, pharmacologically active chemical entities from Egyptian propolis to combat Type 2 DM. Glide docking was utilized for a structure-based virtual screening of the largest in-house library of Egyptian propolis metabolites gathered from literature, in addition to GC-MS analysis of the propolis sample under investigation. Thereafter, combination analysis by means of fixed-ratio combinations of acarbose with propolis and the top chosen propolis-derived phytoligand was implemented. RESULTS: Aucubin, identified for the first time in propolis worldwide and kaempferol were the most promising virtual hits. Subsequent in vitro α-amylase inhibitory assay demonstrated the ability of these hits to significantly inhibit the enzyme in a dose-dependent manner with an IC50 of 2.37 ± 0.02 mM and 4.84 ± 0.14 mM, respectively. The binary combination of acarbose with each of propolis and kaempferol displayed maximal synergy at lower effect levels. Molecular docking and MD simulations revealed a cooperative binding mode between kaempferol and acarbose within the active site. CONCLUSION: The suggested strategy seems imperative to ensure a steady supply of new therapeutic entities sourced from Egyptian propolis to regress the development of DM. Further pharmacological in vivo investigations are required to confirm the potent antidiabetic potential of the studied combination.

Development of a validated HPTLC-bioautographic method for evaluation of aromatase inhibitory activity of plant extracts and their constituents.

INTRODUCTION: Aromatase is a CYP450 enzyme that catalyses the conversion of androgens into oestrogens, where the decrease in the production of oestrogens aided by aromatase inhibitors is considered a target in post-menopausal breast cancer therapy. TLC-bioautography is a technique employed for combining chromatographic separations on TLC plates with bioassays. This is the first report to evaluate aromatase inhibitory activity using this technique. OBJECTIVES: The aim of this study is to develop and validate a new TLC-bioautographic method for determination of aromatase inhibitory activity in 14 plant extracts. Two quantitation methods, the peak area method and reciprocal iso-inhibition volume (RIV) method, were compared and investigated to attain reliable results. Factors affecting the enzymatic reaction (temperature, pH, enzyme and substrate concentrations … etc.) were also investigated to attain the optimum parameters. METHODOLOGY: TLC assisted by digital image processing was implemented for quantitative estimation of the aromatase inhibition of 14 plant extracts using chrysin as positive control. The fluorometric substrate dibenzyl fluorescein (DBF) was utilised for the assay, where inhibitory compounds were visualised as dark spots against a blue fluorescent background. Two software programs, Sorbfil® videodensitometer (in the peak area method) and ImageJ® (in the RIV method), were thoroughly validated using the International Council on Harmonisation (ICH) guideline and used for quantitation. RESULTS: The RIV method showed superiority over the peak area method in the quantitation results of the tracks with non-homogenous background with %RSD values of 0.98 and 1.49 compared with 2.86 and 3.58, respectively. Further, the methods allow the comparison of the activity of different unknown inhibitory compounds without the need for a reference or a positive control. CONCLUSION: Using the TLC-bioautographic method by image processing combined with the RIV quantitation method, simultaneous separation and quantitation of aromatase inhibitory components could be applied to estimate the relative activity of various plant extracts.

Biologically-Guided Isolation of Natural Lead Antithyroid Drug from Medicago sativa L. Sprouts and Its Toxic Profile in Comparison with Propylthiouracil.

Hyperthyroidism is a common endocrine disorder associated with increased risk of cardiovascular complications and mortality. Although antithyroid drugs (ATDs) are approved as first line option for many hyperthyroidism cases, including pregnancy and childhood, they exert significant toxic profile. Medicago sativa L. (alfalfa) also called "The father of all food" was among the diet consumed by mares that gave birth to foals with congenital hypothyroidism. Since, greenfeed was accused for the development of such condition, alfalfa may possess constituents with promising antithyroid potential that could be a valuable substitute for the conventional ATDs. The current work was designed to identify the most biologically active antithyroid phytoconstituent separated from alfalfa sprouts and comparing its antithyroid mechanism, efficacy and toxic profile to the standard ATD; propylthiouracil (PTU). The most biologically active solvent fractions from alfalfa sprouts extract were identified by in vitro screening for anti-thyroid peroxidase (TPO) activity, from which different phytoconstituents were separated and identified by interpretation of spectroscopic data. These compounds were then in vitro screened for anti-TPO and virtually screened via GLIDE XP docking into the crystal structures of the enzymes; bovine lactoperoxidase, as an alternative to TPO, and mammalian selenocysteine-dependent iodothyronine deiodinase (IDI), that are both uniquely dually prohibited by PTU. The compound that showed the least TPO IC50 and highest combined docking XP score was elected for comparing its antithyroid mechanism, efficacy, tendency to reverse hyperthyroidism-triggered complications and toxicity to PTU using L-thyroxine-induced hyperthyroidism model in rats. Seven compounds (1-7) were isolated from the most biologically active fraction, whilst, compounds (4-7) were reported for the first time from alfalfa sprouts. Compound 5 (apigenin) showed the least TPO IC50 and highest in-silico combined score, thus, apigenin was selected for further in-vivo investigations. Apigenin was found to more effectively interfere with type 1-IDI than with TPO in vivo. Apigenin therapy resulted in nearly euthyroid state, without incidence of hypothyroidism, thyroid hypertrophy, hepatotoxity or WBCs count reduction. In addition, apigenin, but not PTU, corrected hyperthyroidism-induced left ventricular hypertyrophy. Therefore, apigenin is a natural lead antithyroid drug that represents a possible safer alternative to conventional ATDs.

Chemometric evaluation of alfalfa sprouting impact on its metabolic profile using HPTLC fingerprint-efficacy relationship analysis modelled with partial least squares regression.

Sprouting is a commonly applied food processing practice specially in Western countries. Tracking the impact of sprouting of Medicago sativa L. (alfalfa) seeds on their phytochemical composition and curative efficacy was implemented in the current study. Sprouting of alfalfa seeds under controlled conditions for eleven days was performed in a biochemical incubator and three samples were randomly taken each day. A total of thirty-six samples (three ungerminated seeds and thirty-three sprouts samples) were collected, extracted and their cytotoxic, antioxidant and antimicrobial activities against five pathogenic microbial strains were measured. Samples were subjected to High performance thin layer chromatography (HPTLC) as a pattern-oriented strategy for metabolite fingerprinting to discover the fluctuations occurring during the sprouting process accompanied by multivariate chemometric analysis. Unsupervised pattern recognition was carried out using Principal Component Analysis (PCA) after extracting the chromatographic fingerprints from HPTLC chromatograms using ImageJ® software. PCA- loading plots demonstrated that luteolin-7-O-glucoside, ferulic acid and P-coumaric acid were the metabolically significant markers. Thus, simultaneous quantification of these crucial three markers in different aged alfalfa seeds/ sprouts extracts was performed using a newly developed and validated HPTLC-image analysis method. The results of the biological activities together with the quantitative data were further subjected to a Partial Least Squares Regression (PLSR) model for implementing HPTLC fingerprint-efficacy relationship analysis. The results obtained from metabolic pool profiling revealed that sprouting can cause remarkable changes in the phytochemical, nutritional and efficacy characteristics of alfalfa seeds.

Digitally-optimized HPTLC coupled with image analysis for pursuing polyphenolic and antioxidant profile during alfalfa sprouting.

The utilization of Folin-Ciocalteu as a post-chromatographic derivatization reagent for direct quantitative estimation of polyphenolic compounds using HPTLC coupled with image analysis was developed, validated and implemented in this study. The phenolic compounds react with Mo+6; the hypothesized active center in molybdotungstophosphoric heteropolyanion causing its reduction into blue colored complex. In addition, a direct TLC-DPPH assay was developed and applied to determine the correlation between the polyphenolic content and their free radical scavenging ability during the sprouting of alfalfa seeds for eleven days. Moreover, different approaches for image to digital conversion routines were studied in this work. Digital camera and flatbed scanner as common in-house image acquisition tools were compared. In addition, three software packages (ImageJ®, JustTLC® and SorbfilTLC®) adopting completely different digitalization algorithms in quantitative image analysis were also competed. Different statistical data revealed that digital camera coupled with ImageJ® program was superior to other investigated approaches regarding linearity, precision, accuracy and detection of polyphenols as well as antioxidants at very low concentration levels.

Integrated in silico-in vitro strategy for screening of some traditional Egyptian plants for human aromatase inhibitors.

ETHNOPHARMACOLOGICAL RELEVANCE: Aromatase enzyme (CYP19) is widely known as a critical target protein for treating hormone-dependent breast cancer. Natural products from traditional medicinal plants continue to be an active source of aromatase inhibitors. Meanwhile, high cost of experimental work and low hit rate associated with HTS have stimulated the implementation of in-silico virtual screening to resolve these pitfalls, where coupling of both classical wet lab procedure and VS may offer a more deepened access to bioactive compounds with less work and time waste. AIM OF THE STUDY: In this work, a sequential structure-based and ligand-based virtual screening strategy was utilized for investigating an in-house database of 1720 phytochemical constituents of 29 medicinal plants and natural products used in traditional Egyptian medicine to search for compounds with the potential to be used as inhibitors of the human aromatase enzyme. MATERIALS AND METHODS: The suggested strategy included using Glide docking with its feature 'extra precision (XP)' for carrying out structure-based virtual screening (SBVS) where the resulting hits were further promoted to ligand-based virtual screening (LBVS) through the development of two pharmacophore and QSAR models; one for steroidal and the other for non-steroidal aromatase inhibitors. RESULTS: The combined results revealed that Artemisia annua, Zingiber officinale, Cicer arietinum, Annona muricata and Vitex agnus castus were the top scoring plants in terms of in-silico activity scores, respectively. The hydro-alcoholic extracts and different solvent fractions of the top scoring plants were subsequently tested experimentally for their aromatase inhibitory activity, by the aid of in-vitro fluorometric assay. The rank ordering of the activities for the plants agreed with the ordering predicted on the basis of SBVS and LBVS workflow implemented. CONCLUSION: The suggested strategy provides a reliable means of prospecting in-silico screening of natural products databases in the search for new dug leads as aromatase inhibitors. The hits so obtained can then be subjected to further phytochemical studies, to isolate and identify suitable compounds for further in-vitro testing.

Cornigerin, a new sesqui-lignan from the hepatoprotective fractions of Cynara cornigera L.

The ethanol extract of Cynara cornigera L. was fractionated and the fractions were subjected to hepatoprotective assays using Wistar albino rats at a dose of 500 and 250mg/kg. The liver injury was induced in rats using carbon tetrachloride. Biochemical parameters such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and total bilirubin were estimated as reflections of the liver condition, with silymarin as a positive control. Phytochemical investigation and chromatographic separation of the hepatoprotective fractions led to the isolation of a new sesqui-lignan namely cornigerin (1), along with eight known compounds: apigenin (2), luteolin (3), ß-sitosterol glycoside (4), apigenin 7-O-ß-D-glucopyranoside (5), luteolin-7-O-ß-D-glucopyranoside (6), apigenin-7-O-rutinoside (7), cynarin 1,5-di-O-caffeoylquinic acid (8), and apigenin-7-O-ß-D-glucuronide (9). This is the first report for the isolation of 8 and 9 from this plant.