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Fig. 1. Results of high-performance liquid chromatography analysis. (A) Chromatogram of mixture of both (1) caffeic acid (CA) and (2) p-coumaric acid (PCA) reference standard compounds. (B) Comparison of chromatogram between APE from Trigona thoracica, CA and PCA as external standards. It demonstrates two peaks at the same wavelength of 300 nm, which are expressed as CA (retention time = 2.117 min) and p-coumaric acid (retention time = 2.799 min). APE: aqueous propolis extract, PPM: part per million.
Korean J Pain 2024;37:141~150 https://doi.org/10.3344/kjp.23318
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