Isolation, RP-UHPLC-ESI-LIT-Orbitrap-MS/MS-Based Metabolic Profiling and Anticandidal Activity of the Root and Leaf Secondary Metabolites of Monotes Kerstingii Gilg (Dipterocarpaceae).

The anticandidal activity of Monotes kerstingii leaf and root crude extracts was evaluated against five clinical Candida isolates: C. albicans, C. parapsilosis, C. krusei, C. glabrata and C. tropicalis. Extracts from both organs displayed Minimal Inhibitory Concentrations (MICs) ranging from 3.9 to 2000 µg/mL. Out of the five Candida species, the leaf hydroethanolic extract (EMKL) was the most active with MIC values of 3.9, 15.6 and 31.5 µg/mL on C. krusei, C. parapsilosis and C. albicans, respectively. The chemical investigation of these extracts led to the characterization of six previously undescribed metabolites, including a glycosylated stilbene: kerstingioside (1), three cis stilbene-coumarins: cis-kerstilbcoumarin A-C (2-4) among which two as inseparable cis/trans-mixtures, one flavanone: kerstingiiflavanone (5) and one fatty acid glycoside, monestoside B (6), alongside with 22 known compounds. The distribution of the annotated metabolites in the roots and leaves was confirmed by comprehensive RP-UHPLC-Orbitrap-MS and MS/MS analysis. In addition, all the isolated compounds were screened for their anticandidal activity. Stilbene 7 was the most active constituent, with MICs of 7.8, 15.6, and 15.6 µg/mL against C. albicans, C. krusei, and C. parapsilosis, respectively, while compounds 14 and 15 exhibited only moderate activity.