Application of a Customised Franz-Type Cell Coupled with HPTLC to Monitor the Timed Release of Bioactive Components in Complex Honey Matrices.

The aim of this study was to assess the release profile of components in five different honeys (a New Zealand Manuka and two Western Australian honeys, a Jarrah honey and a Coastal Peppermint honey) and their corresponding honey-loaded gel formulations using a custom-designed Franz-type diffusion cell in combination with High-Performance Thin-Layer Chromatography (HPTLC). To validate the suitability of the customised setup, release data using this new approach were compared with data obtained using a commercial Franz cell apparatus, which is an established analytical tool to monitor the release of active ingredients from topical semisolid products. The release profiles of active compounds from pure honey and honey-loaded formulations were found to be comparable in both types of Franz cells. For example, when released either from pure honey or its corresponding pre-gel formulation, the percentage release of two Jarrah honey constituents, represented by distinct bands at RF 0.21 and 0.53 and as analysed by HPTLC, was not significantly different (p = 0.9986) at 12 h with over 99% of these honey constituents being released in both apparatus. Compared to the commercial Franz diffusion cell, the customised Franz cell offers several advantages, including easy and convenient sample application, the requirement of only small sample quantities, a large diffusion surface area, an ability to analyse 20 samples in a single experiment, and lower cost compared to purchasing a commercial Franz cell. Thus, the newly developed approach coupled with HPTLC is conducive to monitor the release profile of minor honey constituents from pure honeys and honey-loaded semisolid formulations and might also be applicable to other complex natural-product-based products.

Design, Preparation, and Physicochemical Characterisation of Alginate-Based Honey-Loaded Topical Formulations.

Honey has widespread use as a nutritional supplement and flavouring agent. Its diverse bioactivities, including antioxidant, antimicrobial, antidiabetic, anti-inflammatory, and anticancer properties, have also made it an aspirant natural product for therapeutic applications. Honey is highly viscous and very sticky, and its acceptance as a medicinal product will require formulation into products that are not only effective but also convenient for consumers to use. This study presents the design, preparation, and physicochemical characterisation of three types of alginate-based topical formulations incorporating a honey. The honeys applied were from Western Australia, comprising a Jarrah honey, two types of Manuka honeys, and a Coastal Peppermint honey. A New Zealand Manuka honey served as comparator honey. The three formulations were a pre-gel solution consisting of 2-3% (w/v) sodium alginate solution with 70% (w/v) honey, as well as a wet sheet and a dry sheet. The latter two formulations were obtained by further processing the respective pre-gel solutions. Physical properties of the different honey-loaded pre-gel solutions (i.e., pH, colour profile, moisture content, spreadability, and viscosity), wet sheets (i.e., dimension, morphology, and tensile strength) and dry sheets (i.e., dimension, morphology, tensile strength, and swelling index) were determined. High-Performance Thin-Layer Chromatography was applied to analyse selected non-sugar honey constituents to assess the impacts of formulation on the honey chemical composition. This study demonstrates that, irrespective of the honey type utilised, the developed manufacturing techniques yielded topical formulations with high honey content while preserving the integrity of the honey constituents. A storage stability study was conducted on formulations containing the WA Jarrah or Manuka 2 honey. The samples, appropriately packaged and stored over 6 months at 5, 30, and 40 °C, were shown to retain all physical characteristics with no loss of integrity of the monitored honey constituents.

Monitoring the Release of Methylglyoxal (MGO) from Honey and Honey-Based Formulations.

Methylglyoxal (MGO) is considered to be one of the vital components responsible for the anti-bacterial activity of Leptospermum spp. (Manuka) honey. While many studies have demonstrated a dose-dependent antibacterial activity for MGO in vitro, from a therapeutic viewpoint, it is also important to confirm its release from Manuka honey and also from Manuka honey-based formulations. This study is the first to report on the release profile of MGO from five commercial products containing Manuka honey using a Franz diffusion cell and High-Performance Liquid Chromatography (HPLC) analysis. The release of MGO expressed as percentage release of MGO content at baseline was monitored over a 12 h period and found to be 99.49 and 98.05% from an artificial honey matrix and NZ Manuka honey, respectively. For the investigated formulations, a time-dependent % MGO release between 85% and 97.18% was noted over the 12 h study period.

Optimisation of an agar overlay assay for the assessment of the antimicrobial activity of topically applied semi-solid antiseptic products including honey-based formulations.

The aim of this study was to optimise the so-called agar overlay assay to investigate the antimicrobial activity of some currently available topical antimicrobial products against a range of Gram positive and Gram negative bacteria. During the optimisation process, various assay parameters including base agar volume, overlay agar volume, overlay agar concentration, placement of products into wells or onto coverslip and inoculum concentration were taken into consideration. The optimised assay was found to be a convenient, suitable and effective platform for the assessment of the antimicrobial activity of commercial semi-solid over-the-counter (OTC) products (i.e. non-prescription medicines for topical application used commonly without supervision by a healthcare professional) containing a range of active pharmaceutical ingredients and to be potentially also applicable to complex natural product-based formulations (e.g. honey-based formulation, melaleuca oil-based formulation). The most auspicious aspect of the optimised method was its capability of determining the antimicrobial activity of intact products without further manipulation, unlike other tests that require products to be dissolved or dilute, thus compromising their integrity.

A Review of Commonly Used Methodologies for Assessing the Antibacterial Activity of Honey and Honey Products.

Honey, a naturally sweet and viscous substance is mainly produced by honeybees (Apis mellifera) from flower nectar. Honey exerts a plethora of biological and pharmacological activities, namely, antioxidant, antimicrobial and anti-inflammatory activity, because of the presence of an extensive variety of bioactive compounds. The antibacterial activity is one of the most reported biological properties, with many studies demonstrating that honey is active against clinically important pathogens. As a result, beside honey's widespread utilization as a common food and flavouring agent, honey is an attractive natural antimicrobial agent. However, the use of neat honey for therapeutic purposes poses some problems, for instance, its stickiness may hamper its appeal to consumers and health care professionals, and the maintenance of an adequate therapeutic concentration over a sufficient timeframe may be challenging due to honey liquidity and leakage. It has motivated researchers to integrate honey into diverse formulations, for example, hydrogels, dressings, ointments, pastes and lozenges. The antibacterial activity of these formulations should be scientifically determined to underscore claims of effectiveness. Some researchers have made efforts to adapt the disc carrier and suspension test to assess the antimicrobial activity of topical products (e.g., silver-based wound dressings). However, there is currently no established and validated method for determining the in vitro antimicrobial potential of natural product-based formulations, including those containing honey as the active principle. Against the backdrop of a brief discussion of the parameters that contribute to its antibacterial activity, this review provides an outline of the methods currently used for investigating the antibacterial activity of neat honey and discusses their limitations for application to honey-based formulations.

Antibacterial compounds from the root of the indigenous Australian medicinal plant Carissa lanceolata R.Br.

The conkerberry, Carissa lanceolata R.Br. (Apocynaceae), is commonly used by many indigenous Australian communities across Northern Australia for the treatment of a variety of conditions such as chest pain, toothache, colds and flu. Indigenous uses of this plant strongly argue for an antibacterial bioactivity. The aim is to identify antibacterial compounds from root material of C. lanceolata, therefore confirming the indigenous use of the plant. Antibacterial activity was examined against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Bacillus subtilis using a micro broth dilution technique. Three compounds demonstrating considerable activity were isolated. The volatile phenolic compound 2'-hydroxyacetophenone and the lignan carinol both were reported for the first time from C. lanceolata, whereas this is the second account of the occurrence of carissone. All three compounds showed activity, with 2'-hydroxyacetophenone and carinol having a minimum inhibitory concentration of <1.25 mg mL⁻¹ against all four bacteria. Extracts and compounds isolated from C. lanceolata roots were found to possess a significant antibacterial activity, confirming the indigenous use of this plant.