Chemical and Antifungal Variability of Several Accessions of Azadirachta indica A. Juss. from Six Locations Across the Colombian Caribbean Coast: Identification of Antifungal Azadirone Limonoids

Abstract

Plant materials (i.e., leaves, fruits, and seeds) from 40 trees of Azadirachta indica A. Juss. were collected from six different locations across the Colombian Caribbean coast. Eighty-four ethanolic extracts were prepared and the total limonoid contents (TLiC) and the antifungal activity against Fusarium oxysporum conidia were measured. Their chemical profiles were also recorded via liquid chromatography-electrospray ionization interface-mass spectrometry (LC-ESI-MS) analysis and the top-ranked features were then annotated after supervised multivariate statistics. Inter-location chemical variability within sample set was assessed by sparse partial least squares discriminant analysis (sPLS-DA) and the chemical profiles and biological activity datasets were integrated through single-Y orthogonal partial least squares (OPLS) to identify antifungal bioactives in test extracts. The TLiC and antifungal activity (IC50 values) of the A. indica-derived extracts were found to be ranging from 4.5 to 48.5 mg limonin equivalent per g dry extract and 0.08–44.8 μg/mL, respectively. The presence/abundance of particular limonoids between collected samples influenced the variability among locations. In addition, the integration of chemical and antifungal activity datasets showed five features as markers probably contributing to the bioactivity, annotated as compounds with an azadirone-like moiety. To validate the information provided by the single-Y OPLS model, a high performance liquid chromatography (HPLC)-based microfractionation was then carried out on an active extract. The combined plot of chromatographic profile and microfraction bioactivity also evidenced five signals possessing the highest antifungal activity. The most active limonoid was identified as nimonol 1. Hence, this untargeted metabolite profiling was considered as a convenient tool for identifying metabolites as inter-location markers as well as antifungals against Fusarium oxysporum.

Genomic and chemical evidence for local adaptation in resistance to different herbivores in Datura stramonium

“…First, we identified the seven most abundant constitutive alkaloids in D. stramonium : four tropane alkaloids (atropine, scopolamine, 3‐hydroxy‐6‐tigloyloxytropane, and anisodamine; De‐la‐Cruz et al. 2020), one alkaloid derived from the phenylalanine biosynthesis (phenylacetaldehyde), one pyrrolizidine alkaloid (pyrroline), and one triterpenoid of unknown name but of similar structure and molecular weight to azadirone triterpenoid (Álvarez‐Caballero and Coy‐Barrera 2019) (Supporting Information S2). Each alkaloid was searched and integrated (peak integration) individually in each chromatogram of each plant.…”

Characterization and Antifungal Activity of Limonoid Constituents Isolated from Meliaceae Plants Melia dubia, Aphanamixis polystachya, and Swietenia macrophylla against Plant Pathogenic Fungi In Vitro

“…Nimonol was the best inhibitor; of which inhibition against F. oxysporum conidia germination was observed at IC 50 of 1.48 µM. Alvarez-Caballero and Coy-Barrera (2019) also demonstrated that the presence of a 14, 15-epoxy group and the saturation at 1, 2-olefilic positions in the structure of azadirone-type limonoids led to a diminished effect on fungal conidia germination [11]. In our study, 1, 3, 4, and 5 were isolated and identified as azadirone-type limonoids.…”

“…Over the years, the well-known limonoids and neem extracts were documented as successful examples of botanical insecticides commercialized. Based on the record of known safety, mode of action, and interaction of the limonoid active ingredients, the chemical class is expected to repurpose or use widely for controlling the phytopathogens in organic agriculture [9][10][11][12][13]. However, to our best knowledge, there are very few studies on the activity of Meliaceous limonoids against phytopathogenic fungi.…”

Identification of Antifungal Compounds from Piper Plants Against Fusarium oxysporum: An Untargeted Metabolite Profiling-Based Approach

“…In Vitro Bioassay Against F Oxysporum F oxysporum LQB-03, a virulent isolate obtained from wilting Physalis peruviana plants, was used as the assessed phytopathogen. 43 This isolate had been preserved on Whatman paper # 1 at −20 °C and further reactivated in potato dextrose agar (PDA) to be used in the present antifungal assays. The in vitro antifungal activity against F oxysporum was evaluated by inhibiting mycelial growth (12-well plate amended semisolid medium assay).…”