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

Abstract

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.