Development of solution containing plant extracts for relief of pharyngeal inflammation using mucous-penetrating system

Pharyngitis, well known as sore throat, is the inflammation of pharyngeal tissue which causes swelling and reddening of the tissue. Plant-derived bioactive compounds have been extensively used as herbal recipes in traditional medicine especially in Ayurvedic traditional medicine, Chinese traditional medicine, and Thai traditional medicine. Among 5 herbal plants used for screening the potential extract, the Indian gooseberry extract (IG) and the sappanwood extract (SH) expressed a relatively high antioxidant activity (AOA) and total phenolic content (TPC). The optimization of solvent and method for extracting both herbal plants was accomplished. Therefore, utilizing ethanol in Soxhlet extraction for the extraction of IG and SH gave the greatest condition for obtaining effective compounds. It was then mixed at various mass ratios to prepare the herbal recipes for determining AOA and anti-inflammatory activity (AIA). To the best of the researcher’s knowledge, synergism in AOA (IC50 = 2.97 µg/mL) and AIA (IC50 = 16.38 µg/mL) of the extracts were noticed for the first time in the herbal recipe namely F2. It was selected as an effective herbal recipe (HR) for encapsulating with the niosome nanovesicles. However, the physicochemical stability of HR was investigated under various conditions of pH, ionic strength, and temperature. It was found that HR could be degraded by heat-induced oxidation under an alkaline condition. Nevertheless, it had become more stable when dissolved in an acidic solution containing sodium chloride. Hence, the phosphate-buffered saline pH 5.8 was chosen to be an aqueous phase used for the preparation of HR-loaded niosome. Improving the bioavailability of HR for applying as a solution for the relief of pharyngitis had been achieved by encapsulating in niosome nanovesicles with the incorporation of poloxamer 407 (P407) as a mucous-penetrating agent. The niosome suspensions were successfully prepared using an ethanol injection method. The encapsulation efficiency and the particle size were determined to be ranged from 2.07 - 9.11 % and 27.97 - 359.03 nm, respectively. In vitro release using mucin as a mucus model and the mathematical modeling revealed that the release mechanism of niosome suspension prepared without P407 relied on the diffusion of HR. Meanwhile, the incorporation of P407 resulted in a release mechanism of non-Fickian transport might cause by the presence of the mucous-penetrating agent. Here the researcher has shown that the obtained niosome suspensions are the promising solution for validating the effectiveness against pharyngitis in the future.