Objectives: Medicated oil has been traditionally used as an analgesic medicine to relieve pain by applying to the skin over painful muscles, and has been established in The National List of Essential Medicines (2556 B.E.). Traditional Medicated oil (TMO) consists of cassumunar ginger, Wan En Lueang, and Wan Ron Thong. It is prepared by frying herbs in coconut oil which is a traditional method. Thai Herbal Medicated oil formula (MOF) comprises cassumunar ginger, sweet flag, lesser galangal, wild turmeric, Wan En Lueang, and Wan Ron Thong. Its preparation by maceration with methyl salicylate is modified method to avoid the heat in the traditional preparation. Since both recipes have different methods of extraction and compositions, it is necessary to determine the chemical constituents and acute skin irritation potential of MOF and TMO.
Methods: This study applied Gas Chromatography-Mass Spectrometry (GC-MS) for quality assessment of MOF extract and TMO extract. The mass spectra of the compounds matched with authentic standards from the NIST library. The compounds were identified by comparing their retention time and peak area, and the percentage of matched factor was more than 80%. The safety assessment on acute skin irritation used the 4 h human patch test (4 h HPT) in 36 healthy subjects.
Results: The 37 compounds were found in MOF extract. The most common chemical constituents were terpene derivatives; monoterpenes and sesquiterpenes, and others, namely benzene derivatives, ester, phenylpropanoid, and other compounds. The 33 compounds were found in TMO extract and the chemical groups were similar to MOF extract. The 4 h HPT demonstrated that the MOF extract, TMO extract, methyl salicylate solvent, and coconut oil solvent, did not induce skin irritation. However, the vehicle of the formulae and the whole formulae as MOF and TMO clinically induced skin irritation and accorded with rubefacient. The characteristic as mild erythema or dryness, but not erythema with edema, could appear after the use of rubbing skin products.
Conclusions: The chemical constituents found in MOF and TMO extracts were partially different and their acute skin irritation reactions were not significantly different. A study on the efficacy of both remedies should be performed in the future, as well as a study on active chemical constituents. This study provides scientific evidences of quality and safety, including GC-MS condition for poly-herbal medicated oil standardization.
Keywords: Thai herbal formula; gas chromatography-mass spectrometry; medicated oil; skin irritation.
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