Formulation, characterization and anti-malarial activity of homolipid-based artemether microparticles

Irvingia gabonensis baill. (African Mango): A comprehensive review of its ethnopharmacological significance, unveiling its long-standing history and therapeutic potential

ETHNOPHARMACOLOGICAL RELEVANCE

Irvingia gabonensis (Aubry-Lecomte ex O'Rorke) Baill. (IG) is a multipurpose tree native to tropical Africa such as Equatorial Guinea, Nigeria, Gabon, and Cameroon with high ethnomedicinal values.

AIM OF THE STUDY

This review emphasizes the ethnopharmacological significance, phytochemical, and functional properties of African mango, focusing on its potential for human health and industrial applications.

MATERIALS AND METHODS

Literature published on IG was traced by different databases, including the Egyptian Knowledge Bank database (EKB), ScienceDirect, PubMed, Google Scholars, Research Gate, Web of Science, Elsevier, and Scopus. Numerous keywords were used to achieve an inclusive search in the databases, like 'African Mango', 'Bush Mango', 'Irvingia gabonensis', 'Wild Mango', 'Dika Nut', 'Phytochemistry', 'Traditional uses', 'Functional foods', 'Polyphenols', 'Ogbono', 'Ellagic acid and its derivatives', and 'Pharmacological activities'.

RESULTS

Different parts of IG have been employed in traditional medicine and recorded a great success. The ripe fruit pulp was consumed fresh or processed into juice and wine documented for anti-diarrheal, anti-diabetic, anti-ulcer, hepatoprotective, antimicrobial, and anti-inflammatory properties. The kernels, which are widely traded and incorporated into traditional dishes, remain an integral part of culinary traditions. Seeds have folkloric uses for weight loss and are popular as blood thinners and anti-diabetics. Where the bark is reported for dysentery, colic, scabies, toothache, and various skin conditions. In Senegal, the stem bark is employed for gonorrhea, hepatic disorders, and gastrointestinal ailments. The leaves possess the potential to enhance renal and hepatic functions, safeguarding these vital organs against the detrimental effects of toxic substances. Pulp is rich in vitamin C, carbohydrates, and proteins. Oil is the major constituent of the seed, which is mainly composed of myristic and lauric acids. The defatted extracts are characterized by flavonoid glycosides and ellagic acid derivatives. Despite their widespread use, IG extracts are still inadequately characterized phytochemically and merit further investigation within the realm of scientific research. Encouragingly, toxicity studies have demonstrated the relative safety of IG extract at the administered doses.

CONCLUSION

The review extends our knowledge of the health benefits of IG, where these effects could be attributed to the phytochemicals present.

Opportunity in nanomedicine to counter the challenges of current drug delivery approaches used for the treatment of malaria: a review

Malaria is a life-threatening parasitic disease transmitted by the infected female Anopheles mosquito. The development of drug tolerance and challenges related to the drugs' pharmacodynamic and pharmacokinetic parameters limits the antimalarial therapeutics response. Currently, nanotechnology-based drug delivery system provides an integrative platform for antimalarial therapy by improving the drug physicochemical properties, combating multidrug resistance, and lowering antimalarial drug-related toxicity. In addition, surface engineered nanocarrier systems offer a variety of alternatives for site-specific/targeted delivery of antimalarial therapeutics, anticipating better clinical outcomes at low drug concentrations and low toxicity profiles, as well as reducing the likelihood of the emergence of drug resistance. So, constructing nano carrier-based approaches for drug delivery has been considered the foremost strategy to combat malaria. This review focuses on the numerous nanotherapeutic strategies utilised to treat malaria as well as the benefits of nanotechnology as a potentially effective therapeutic.

Comparison of the In Vitro Drug Release Methods for the Selection of Test Conditions to Characterize Solid Lipid Microparticles

The release profiles of active substances from microspheres are one of the most important features in solid lipid microparticles (SLM) characterization. Unfortunately, the results of the dissolution tests are largely dependent on the chosen method and test conditions, which in relation to novel dosage forms, such as dispersions of lipid microspheres, are not clearly defined in international compendiums and guidelines. This makes it impossible to compare the results of different studies. The aim of the research was to identify the factors most influencing the variability of the obtained results. An attempt was also made to select the most appropriate method for testing drug substance release from SLM. Various dissolution methods were employed (method I: without a membrane, method II: in a dialysis bag, and method III: in a Side-Bi-Side chamber), and the obtained release profiles of cyclosporine and indomethacin from SLM dispersions were compared. In addition to the effect of membranes, the types of acceptor fluids were also investigated. Significant differences were observed when testing the SLM formulations under various test conditions. The results were significantly influenced by the selected membrane, the acceptor fluid, or the difference in the concentrations of active substance between the donor and acceptor compartments. The burst effect observed in some experimental methods was not noticed in other conditions. At this stage, the method with a dialysis bag has been selected as the most suitable, while the methods without the membrane can only play a complementary role.

Development and formulation of antidiabetic property of Anarcadium occidantale-based solid lipid microparticles

Anacardium occidentale (AO) possesses potent anti-diabetic properties, owing to its high phytochemicals content. This study attempted to maximise the efficacy of AO by encapsulating it in a solid lipid microparticle (SLMs) formulation. Leaves of AO were extracted with water and formulated into SLMs using a lipid matrix composed of P90H and Dika fat. Characterisation of the SLMs include morphology, particle size, pH, encapsulation efficiency percentage, in vitro release and anti-diabetic properties. SLMs were spherical with sizes ranging from 16.7 ± 0.8 µm to 40.12 ± 2.34 µm and had a fairly stable pH over time. Highest drug entrapment was 87%_. Batch A₂ exhibited an even release of 89%, sustained over time, and a mean percentage reduction in glucose of 25.9% at 12 h after oral administration to study animals. Anacardium occidentale-loaded SLMs exhibited a good hypoglycaemic effect and can be used in the management of diabetes.

Exploitation of capsule system for colon targeted drug delivery of biopolymer-based microparticles: in vivo and in vitro applications

The current study was to improve and control aceclofenac delivery prepared as biopolymer-based microparticles for effective colon-targeted drug delivery using modified gelatin capsules (MGCs) at different time intervals developed in two batches (C1 and C2). Microparticles were formulated with extracted mucuna gum using liquid paraffin oil (AC.LPO) and soybean oil (AC.SO) and evaluated in vitro for physicochemical performance and in vivo in rats. Encapsulation efficiency ranges from 54.48 ± 0.21% to 82.83 ± 0.22% for AC.LPO and 52.64 ± 0.11% to 80.36 ± 0.22% for AC.SO. SEM showed oblong and irregular shapes with porous and cracked surfaces. DSC showed low enthalpy and a very broad endothermic peak depicting high amorphous property. Delayed drug release was observed in the upper gastrointestinal tract with sustained release depicted in the lower gastrointestinal tract (GIT) using 3 and 9-h batch C1 of MGCs. AC.SO exhibited significantly (p < 0.05) higher anti-inflammatory activity (86%) than AC.LPO (77%). Hence, aceclofenac colon delivery could be improved and controlled using biopolymer-based colon-targeted microparticles delivered with MGCs.

Distribution of Drug Substances in Solid Lipid Microparticles (SLM)—Methods of Analysis and Interpretation

The incorporation of drug substances into the matrix of solid lipid microparticles (SLM) is critical to providing effects such as prolonged release, taste masking, and protection of the labile API. Currently, a commonly used method of characterizing multi-compartment lipid systems, such as SLM, is to determine entrapment efficiency (EE) and drug loading (DL) parameters, but this is not sufficient for understanding the localization of API either in the core or on the surface of the microspheres. The main objective of the research was to study the distribution of API in an aqueous dispersion of SLM in order to distinguish between the API incorporated in the lipid matrix and localized in the superficial region (interphase) and to refer the obtained results to the EE and DL parameters. SLM dispersions (10–30% of the lipid) with four model drug substances, i.e., cyclosporine, clotrimazole, diclofenac sodium and hydrocortisone, were prepared and investigated. In the first stage, the experiments were designed to optimize the method of extracting the API fraction localized on the SLM surface by shaking the dispersions with methanol. The fraction dissolved in the aqueous phase was obtained by ultrafiltration of SLM dispersions. Total drug content and the concentration in the separated phases were determined by the HPLC method. The obtained results were compared with the EE and DL parameters. Selected SLM dispersions were tested both before and after thermal sterilization. Short-term shaking of SLM dispersion with methanol does not damage the lipid matrix and allows the API fraction localized on the SLM surface to be extracted, the result of which was the determination of API distribution between lipid matrix, interphase and aqueous phase. It was found that the majority of API represented by EE value was localized on the surface of SLM. Only for cyclosporine was the incorporation of drug molecules in the lipid core very effective (up to 48%), while for other drug substances only 1–21% was found in the lipid core of SLM. A clear influence of the sterilization process on the distribution of API within the microparticles was found. The presented studies showed that the characterization of multi-compartment SLM dispersions solely on the basis of EE and DL values, is insufficient. The proposed new distribution test method enables the localization of API to be demonstrated within the microspheres, with the quantitative characteristics of the drug fraction incorporated in the lipid matrix and the fraction associated with the surface of the lipid matrix. The proposed new method allows the influence of the sterilization process on the changes in the API distribution within the lipospheres to be evaluated. Such characteristics provide new opportunities for the development and use of this dosage form as a carrier providing prolonged release and other aforementioned advantages.

Formulation and evaluation of transdermal nanogel for delivery of artemether

Artemether (ART) is second to artesunate in being the most widely used derivatives of artemisinin in combination therapy of malaria. Nanostructured lipid carrier (NLC) formulations were prepared following our previous report using optimized ART concentration of 0.25 g dissolved in 5% w/v mixture of solid (Gelucire 43/01 and Phospholipon 85G) and liquid (Transcutol) lipids at 90 °C. An aqueous surfactant phase at 90 °C was added (dropwise) under magnetic stirring (1000 rpm) for 5 min. The pre-emulsion was speedily homogenized at 28,000 rpm for 15 min and further probe sonicated at 60% amplitude (15 min). Resultant sample was cooled at room temperature and frozen at - 80 °C prior to lyophilization. The freeze-dried sample was used for solid-state characterization as well as in the formulation of transdermal nanogels using three polymers (Carbopol 971P, Poloxamer 407, and Prosopis africana peel powder) to embed the ART-NLC, using ethanol as a penetration enhancer. Transdermal ART-nanogels were characterized accordingly (physical examination, pH, drug content, rheology, spreadability, stability, particle size and morphology, skin irritation, in vitro and ex vivo skin permeation, and analysis of permeation data), P < 0.05. Results indicated that ART nanogels showed good encapsulation, drug release, pH-dependent swelling, stability, and tolerability. Overall, ART nanogels prepared from Poloxamer 407 showed the most desirable drug permeation, pH, swellability, spreadability, viscosity, and transdermal antiplasmodial properties superior to PAPP-ANG > C971P-ANG. A two-patch/week concurrent application of the studied nanogels could offer 100% cure of malaria as a lower-dose (50 mg ART) patient-friendly regimen devoid of the drug's many side effects.

Artemisinin inhibits TLR4 signaling by targeting co-receptor MD2 in microglial BV-2 cells and prevents lipopolysaccharide-induced blood-brain barrier leakage in mice

Artemisinin and its derivatives have been the frontline drugs for treating malaria. In addition to the antiparasitic effect, accumulating evidence shows that artemisinins can alleviate neuroinflammatory responses in the central nervous system (CNS). However, the precise mechanisms underlying their anti-neuroinflammatory effects are unclear. Herein we attempted to delineate the molecule target of artemisinin in microglia. In vitro protein intrinsic fluorescence titrations and saturation transfer difference (STD)-NMR showed the direct binding of artemisinin to Toll-like receptor TLR4 co-receptor MD2. Cellular thermal shift assay (CETSA) showed that artemisinin binding increased MD2 stability, which implies that artemisinin directly binds to MD2 in the cellular context. Artemisinin bound MD2 showed much less collapse during the molecular dynamic simulations, which supports the increased stability of MD2 upon artemisinin binding. Flow cytometry analysis showed artemisinin inhibited LPS-induced TLR4 dimerization and endocytosis in microglial BV-2 cells. Therefore, artemisinin was found to inhibit the TLR4-JNK signaling axis and block LPS-induced pro-inflammatory factors nitric oxide, IL-1β and TNF-α in BV-2 cells. Furthermore, artemisinin restored LPS-induced decrease of junction proteins ZO-1, Occludin and Claudin-5 in primary brain microvessel endothelial cells, and attenuated LPS-induced blood-brain barrier disruption in mice as assessed by Evans blue. In all, this study unambiguously adds MD2 as a direct binding target of artemisinin in its anti-neuroinflammatory function. The results also suggest that artemisinin could be repurposed as a potential therapeutic intervention for inflammatory CNS diseases.

Analytical Techniques for the Assessment of Drug-Lipid Interactions and the Active Substance Distribution in Liquid Dispersions of Solid Lipid Microparticles (SLM) Produced de novo and Reconstituted from Spray-Dried Powders

Solid lipid microparticles (SLM) can be presented as liquid suspension or spray-dried powder. The main challenge in SLM technology is to precisely determine the location of the active substance (API) in the different compartments of the formulation and its changes during SLM processing. Therefore, the purpose of the research was to assess the distribution of the API and to investigate the nature of the API-lipid interaction when the formulation was subjected to spray drying, with an indication of the most suitable techniques for this purpose. SLM were prepared with two various lipids (Compritol or stearic acid) and two model APIs: cyclosporine (0.1% and 1% w/w) and spironolactone (0.1% and 0.5% w/w). Physicochemical characterizations of the formulations, before and after spray drying, were performed by differential scanning calorimetry (DSC), atomic force microscopy (AFM), Raman spectroscopy and nuclear magnetic resonance (NMR). The API distribution between the SLM matrix, SLM surface and the aqueous phase was determined, and the release study was performed. It was demonstrated that, in general, the spray drying did not affect the drug release and drug distribution; however, some changes were observed in the SLM with Compritol and when the API concentration was lower. Only in the SLM with stearic acid was a change in the DSC curves noted. Measurements with the AFM technique proved to be a useful method for detecting differences in the surface properties between the placebo and API-loaded SLM, while the Raman spectroscopy did not show such evident differences.

Preparation, characterisation and in vitro antibacterial property of ciprofloxacin-loaded nanostructured lipid carrier for treatment of Bacillus subtilis infection

Context: In this study, controlled ciprofloxacin (CIPRO) nanostrustructured lipid carriers of Precirol^® ATO 5/Transcutol^® HP (batch A) and tallow fat/Transcutol^® HP (batch B) was carreid out. Objective: The aim was to improve solubility and bioavailability of CIPRO. Objective: Study of controlled ciprofloxacin (CIPRO) nanostructured lipid carriers of Precirol^® ATO 5/Transcutol^® HP (batch A) and tallow fat/Transcutol^® HP (batch B). Methods: CIPRO concentrations C_1-5 (0.0, 0.2, 0.5, 0.8, and 1.0% w/w) as AC_1-5 and BC_1-5 were prepared by hot homogenisation and characterised by zetasizer, differential scanning calorimetry, Fourier transform infra-red spectroscopy, in vitro drug release and growth inhibitory zone diameter (IZD) on agar-seeded Bacillus subtilis. Results: AC₅ achieved polydispersed particles of ∼605 nm, 92% encapsulation efficiency (EE) and -28 mV similar to BC₅ (∼789 nm, 91% EE, and -31 mV). Crystallinity indices (AC₅ and BC₅) were low at 3 and 5%, respectively. CIPRO release in AC₅ was ∼98% in SGF (pH 1.2) and BC₅ similarly ∼98% in SIF (pH 6.8). Conclusions: AC₅ had superior growth inhibition of B. subtilis at lower concentration (1.2 µg/mL) than BC₅ and CIPRO controls; hence could serve as possible sustained delivery system of CIPRO.

Characteristics of Artemether-Loaded Poly(lactic-co-glycolic) Acid Microparticles Fabricated by Coaxial Electrospray: Validation of Enhanced Encapsulation Efficiency and Bioavailability

Artemether is one of the most effective drugs for the treatment of chloroquine-resistant and Plasmodium falciparum strains of malaria. However, its therapeutic potency is hindered by its poor bioavailability. To overcome this limitation, we have encapsulated artemether in poly(lactic-co-glycolic) acid (PLGA) core-shell microparticles (MPs) using the coaxial electrospray method. With optimized process parameters including liquid flow rates and applied electric voltages, experiments are systematically carried out to generate a stable cone-jet mode to produce artemether-loaded PLGA-MPs with an average size of 2 μm, an encapsulation efficiency of 78 ± 5.6%, and a loading efficiency of 11.7%. The in vitro release study demonstrates the sustained release of artemether from the core-shell structure in comparison with that of plain artemether and that of MPs produced by single-axial electrospray without any relevant cytotoxicity. The in vivo studies are performed to evaluate the pharmacokinetic characteristics of the artemether-loaded PLGA-MPs. Our study implies that artemether can be effectively encapsulated in a protective shell of PLGA for controlled release kinetics and enhanced oral bioavailability.

Sustained-release liquisolid compact tablets containing artemether-lumefantrine as alternate-day regimen for malaria treatment to improve patient compliance

The present study aimed to develop low-dose liquisolid tablets of two antimalarial drugs artemether–lumefantrine (AL) from a nanostructured lipid carrier (NLC) of lumefantrine (LUM) and estimate the potential of AL as an oral delivery system in malariogenic Wistar mice. LUM-NLCs were prepared by hot homogenization using Precirol^® ATO 5/Transcutol^® HP and tallow fat/Transcutol^® HP optimized systems containing 3:1 ratios of the lipids, respectively, as the matrices. LUM-NLC characteristics, including morphology, particle size, zeta potential, encapsulation efficiency, yield, pH-dependent stability, and interaction studies, were investigated. Optimized LUM-NLCs were mixed with artemether powder and other dry ingredients and the resultant powder evaluated for micromeritics. Subsequent AL liquisolid tablets were tested for in vitro drug release and in vivo antiplasmodial activity in mice infected with Plasmodium berghei berghei (NK 65). Results showed that optimized LUM-NLC were stable, spherical, polydispersed but nanometric. Percentage yield and encapsulation efficiency were ~92% and 93% for Precirol^® ATO 5/Transcutol^® HP batch, then 81% and 95% for tallow fat/Transcutol^® HP batch while LUM was amorphous in NLC matrix. In vitro AL release from liquisolid compacts revealed initial burst release and subsequent sustained release. Liquisolid tablet compacts formulated with Precirol^® ATO 5/Transcutol^® HP-AL4 achieved higher LUM release in simulated intestinal fluid (84.32%) than tallow fat/Transcutol^® HP-BL3 (77.9%). Non-Fickian (anomalous) diffusion and super case II transport were the predominant mechanisms of drug release. Equal parasitemia reduction was observed for both batches of tablet compacts (~92%), superior to the reduction obtained with commercial antimalarial formulations: Coartem^® tablets (86%) and chloroquine phosphate tablets (66%). No significant difference (P<0.05) in parasite reduction between double (4/24 mg/kg) and single (2/12 mg/kg) strength doses of AL compacts was observed. Our result highlights that AL could be formulated in much lower doses (4/24 mg/kg), for once-in-two days oral administration to improve patient compliance, which is currently not obtainable with conventional AL dosage forms.

Solid lipid nanoparticles encapsulating a fluorescent marker (coumarin 6) and antimalarials – artemether and lumefantrine: evaluation of cellular uptake and antimalarial activity

Artemisinins, the mainstay in the treatment of malaria today, are used in combination with other antimalarials to forestall resistance, as artemisinin-combination therapies. In line with the World Health Organization’s recommendation in that respect, solid lipid nanoparticles (SLN) were formulated to encapsulate two antimalarial drugs — artemether and lumefantrine. The nanoparticles were evaluated for size and solid state properties. Caco-2 cells were used to investigate the ability of the SLN to deliver its payload at the absorptive interface of the gastrointestinal tract. Mice heart endothelial cells (MHEC) were also used as marker cells to assess cellular uptake of coumarin 6 from the SLN with imaging by confocal laser scanning microscopy (CSLM). In vivo antimalarial activity was done using a standard suppressive protocol. The results of this study revealed different crystal properties for artemether and lumefantrine, which affected their solubility in the lipid matrix and thus, loading in the lipid nanoparticles. The particles of the SLN were within the range of 150 nm–500 nm with varied polydispersity indices. Wide angle X-ray diffraction analysis indicated the presence of particles of solid nature. Cellular uptake studies indicated uptake of coumarin 6 from the coumarin 6-labeled SLN. In vivo antimalarial studies indicated high clearance of parasitemia with minimal effect on hematological parameters tested.