Methylglyoxal (MGO) is an essential component of Manuka honey that contributes to its antibacterial activity. While previous studies have demonstrated the antibacterial effects of MGO in vitro, it is important to understand its release from Manuka honey and honey-based products for therapeutic purposes. This study investigated 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 results showed that MGO was released from an artificial honey matrix and pure Manuka honey at a rate of 99.49% and 98.05% respectively over a 12-hour period. The release of MGO from the commercial formulations ranged from 85% to 97.18% over the same period. These findings provide valuable insights into the release of MGO from Manuka honey-based products and their potential therapeutic efficacy.

Keywords: release profile, methylglyoxal, honey-based formulation, Franz diffusion cell, High-Performance Liquid Chromatography

Introduction

Honey is a natural substance produced by bees from the nectar of flowers or the exudation of plants or insect excretions. It has been used for its medicinal properties for thousands of years due to its antibacterial, antioxidant, anticancer, antiparasitic, antiviral, and antidiabetic effects. The therapeutic potential of honey is attributed to its complex compound profile, including phenolic compounds, organic acids, enzymes, minerals, and other minor constituents. The antibacterial activity of honey is primarily due to its high osmolarity, acidity, enzymatic generation of hydrogen peroxide (H2O2) and nitric oxide (NO), and the presence of other minor constituents such as phenolics, flavonoids, and organic acids.

Manuka honey, derived from the Leptospermum species, is known for its non-peroxide antibacterial activity, which is mainly attributed to the presence of methylglyoxal (MGO). MGO is formed during the maturation, storage, and processing of honey from the dehydration of a precursor molecule called dihydroxyacetone (DHA). The therapeutic effects of honey-based medicinal products are expected to be influenced by the release of active components such as MGO from the formulation matrix upon topical application.

The Franz diffusion cell is a commonly used tool to evaluate the in vitro release of drugs from topical dosage forms. In this study, a Franz diffusion cell and HPLC analysis were used to monitor the release of MGO from Manuka honey and commercial honey-based products. The release profile of MGO was determined over a 12-hour period, and the results provide insights into the release kinetics and potential therapeutic efficacy of these products.

Materials and Methods

Samples

Five commercial products containing Manuka honey as the active ingredient were purchased from pharmacies and veterinary product suppliers in Australia. The products had different applications, including wound healing, burns, and dry eye symptoms.

Chemicals and Reagents

HPLC-grade acetonitrile (ACN), hydroxyacetone (HA), methylglyoxal (MGO) solution, and o-(2,3,4,5,6-Pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA) were used in the analysis.

In Vitro Release of MGO

The release of MGO was evaluated using a Franz diffusion cell with a dialysis membrane as a mimic for skin. The donor and receptor compartments were filled with phosphate-buffered saline (PBS), and the samples were applied to the membrane surface. Samples were collected at various time points over a 12-hour period, and the MGO release was determined using HPLC analysis.

HPLC Analysis of Released MGO

HPLC analysis was performed using a diode array detector, a Gemini NX-C18 column, and a mobile phase consisting of acetonitrile and water. The MGO content in the collected samples was determined by preparing standards and using a calibration curve. The MGO release profile was analyzed based on the peak area ratios of MGO to the internal standard.

Statistical Analysis

Statistical analysis was performed using Graphpad Prism software. Analysis of variance (ANOVA) and Tukey’s post hoc test were used to determine significant differences between the samples.

Results

The baseline MGO content varied among the investigated formulations, indicating variations in the MGO levels of Manuka honeys. The release of MGO from the honey matrix and pure Manuka honey was found to be approximately 99.49% and 98.05% respectively over a 12-hour period. The release of MGO from the commercial formulations ranged from 85% to 97.18% over the same period. The excipients in the commercial products had mixed effects on the release of MGO, with some formulations showing lower release compared to others. The presence of oils and waxes as excipients in two formulations may have contributed to the lower release of MGO.

Discussion

In vitro release studies are important for understanding the performance and quality of pharmaceutical dosage forms. For honey-based products, the release of active components from the formulation matrix is crucial for their therapeutic efficacy. This study investigated the release profile of MGO from Manuka honey and commercial honey-based products. The results showed that MGO was released from the honey matrix and commercial formulations over a 12-hour period. The release of MGO was influenced by the honey matrix itself and the presence of excipients in the commercial products. The slow and time-dependent release of MGO observed in this study may be advantageous for wound healing applications.

Conclusion

This study provides insights into the release profile of MGO from Manuka honey and honey-based products. The results demonstrate the time-dependent release of MGO from the honey matrix and commercial formulations over a 12-hour period. These findings contribute to our understanding of the therapeutic efficacy of Manuka honey-based products and their potential application in wound healing. Further research is needed to explore the release kinetics and bioavailability of MGO in different formulations to optimize their therapeutic effects.