A Novel Multilayer Natural Coating for Fed-State Gastric Protection

Several nutraceutical products require gastric protection against the hostile environment in the stomach. Currently marketed synthetic and semi-synthetic coatings suffer from major shortcomings such as poor gastric protection, slow-release response to pH change, and the use of artificial ingredients. The challenge of coating natural products is further exacerbated by the relatively high gastric pH in the fed state.

In this work, a novel natural enteric coating is presented as a breakthrough alternative to current solutions. Two coating systems were devised: (i) a triple-layer coating that comprises a wax layer embedded between two alginate-based coatings, and (ii) a double-layer coating, where an overcoat of organic acids (fumaric or citric acid) is applied to an alginate-based coating. The multi-layer architecture did not impact the pH-responsive nature of the coating even when more biologically relevant Krebs bicarbonate buffer of lower buffer capacity was used.

Interestingly, the gastric protection barrier of organic acid-based coating remained resistant at elevated gastric pH 2, 3, or 4 for 2 h. This is the first report of using an alginate-based coating to provide gastric protection against fed-state stomach conditions (pH 2–4). Being biodegradable, naturally occurring, and with no limit on daily intake, the reported novel coating provides a superior platform to current coating solutions for pharmaceutical and nutraceutical products.

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Materials: Anhydrous theophylline was purchased from Acors Organics. The excipients used for tablet compression were: directly compressible lactose monohydrate—Lactopress (BASF SE, Ludwigshafen, Germany), polyvinylpyrrolidone K90 (Sigma-Aldrich, Dorset, UK), microcrystalline cellulose (MCC) PH101 (FMC Biopolymer, Woluwe-Saint-Lambert, Belgium), cross-carmellose sodium SD-711 (FMC Biopolymer, Belgium), and magnesium stearate (Sigma–Aldrich Co., Ltd., Dorset, UK). The coating components were: sodium alginate (Alg, 15–20 cps) supplied by Sigma-Aldrich (Dorset, UK), ceresin wax supplied by Fisher Scientific (UK), glyceryl monostearate (Imwitor® 900K, GMS) donated by Cremer OLEO (Hamburg, Germany), citric acid monohydrate and pectin from citrus supplied by Sigma-Aldrich (USA), and fumaric acid purchased from Fischer Scientific (USA).

Article information: Habashy, R.; Khoder, M.; Isreb, A.; Alhnan, M.A. A Novel Multilayer Natural Coating for Fed-State Gastric Protection. Pharmaceutics 2022, 14, 283. https://doi.org/10.3390/pharmaceutics14020283