Even though there are reported methods for the quantification of free amino acids (FAAs) in biological products, no work has been done on the analysis of these substances in formulations. Moreover, further research is required as the reported methods do not fulfill analytical method requirements. The objective of this study was, therefore, to develop and validate a rapid, reliable, and appropriate RP-HPLC/DAD method for the simultaneous determination of 18 FAAs (l-Ala, l-Arg, l-Asn, l-Asp, l-Gln, l-Glu, l-Gly, l-His, l-Ile, l-Lue, l-Lys, l-Met, l-Orn, l-Phe, l-Pro, l-Ser, l-Thr, and l-Val) in topical formulations. After appropriate method development, the technique was validated for selectivity, linearity and range, limit of detection, limit of quantification, precision, and accuracy. The samples were derivatized with 9-fluorenylmethyl chloroformate (Fmoc-Cl). Chromatographic separation was performed on InfinityLab Poroshell 120 E.C 18 (3 × 50) mm, 2.7 μm column at 25 °C. The mobile phase consisting of water and acetonitrile adjusted to appropriate pH was pumped in gradient mode at a flow rate of 0.7 mL/min. Ten microliters were injected and analyte detection was conducted using a DAD. The results indicate that the method was selective for these FAAs. It was linear over the concentration range of 5–80 µM with a correlation coefficient greater than 0.995. Moreover, it was sensitive, precise, accurate, and robust. All the reported drawbacks of RP-HPLC-based analysis of FAAs were resolved, and hence, this new method can be considered appropriate for the analysis of these FAAs in topical formulations.

Free amino acids (FAAs), the major constituents of the natural moisturizing factor (NMF), are very important for maintaining the moisture balance of human skin and their deficiency results in dry skin conditions. There is a great interest in the identification and use of nature-based sources of these molecules for such cosmeceutical applications. The objective of the present study was, therefore, to investigate the FAA contents of selected Ethiopian plant and fungi species; and select the best sources so as to use them for the stated purpose. About 59 different plant species and oyster mushroom were included in the study and the concentrations of 27 FAAs were analyzed. Each sample was collected, lyophilized, extracted using aqueous solvent, derivatized with Fluorenylmethoxycarbonyl chloride (Fmoc-Cl) prior to solid-phase extraction and quantified using Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometric (LC-ESI–MS/MS) system. All the 27 FAAs were detected in most of the samples. The dominant FAAs that are part of the NMF were found at sufficiently high concentration in the mushroom and some of the plants. This indicates that FAAs that could be included in the preparations for the management of dry skin condition can be obtained from a single natural resource and the use of these resources for the specified purpose have both economic and therapeutic advantage in addition to fulfilling customer needs.