UHPLC-ESI-QTOF-MS/MS profiling of saponins and tyrosinase inhibitory activity of Ilex cochinchinensis, Ilex annamensis, and Ilex rotunda leaves from Vietnam

Abstract

In this study, a rapid and sensitive UHPLC-ESI-QTOF-MS/MS method was established to characterize and differentiate saponin profiles in the leaves of Ilex cochinchinensis, Ilex annamensis, and Ilex rotunda collected in Vietnam. This is the first report on the chemical composition of I. cochinchinensis and I. annamensis using this advanced analytical approach. A total of 63 saponins were tentatively identified across all samples, with I. cochinchinensis, I. annamensis, and I. rotunda containing 39, 30, and 34 compounds, respectively. Among these, seven saponins were newly reported from I. cochinchinensis, including two novel structures corresponding to compound 9 at a retention time (RT) of 11.83 minutes, one novel structure corresponding to compound 15 at RT 12.09 minutes, and four novel structures corresponding to compound 46 at RT 13.71 minutes. Notably, compound 46 was also detected in I. annamensis, whereas no new saponins were identified in I. rotunda. Saponin profiles allowed clear differentiation among the three species. Additionally, we evaluated the tyrosinase inhibitory activity of methanolic leaf extracts at 100 μg mL⁻¹. I. annamensis exhibited the highest inhibition (40.70% ± 1.84), followed by I. cochinchinensis (24.40% ± 1.27) and I. rotunda (14.43% ± 1.53). These findings not only expand the phytochemical database of Vietnamese Ilex species but also highlight the potential of I. annamensis as a promising source of natural tyrosinase inhibitors for cosmetic and dermatological applications.