Insecticidal Activity of Trichilia hirta L. (Sapindales: Meliaceae) Extracts Against Spodoptera frugiperda (Lepidoptera: Noctuidae) Larvae and the Identification of Bioactive Compounds

TL;DR

This study shows that Trichilia hirta plant extracts are highly effective against Spodoptera frugiperda larvae and identifies specific compounds responsible for this insecticidal activity.

Contribution

The first identification of noreugenin in the Trichilia genus and the discovery of bioactive compounds in T. hirta against a major pest.

Findings

The crude methanolic extract of T. hirta caused 100% larval mortality in Spodoptera frugiperda.

The ethyl acetate fraction showed the highest insecticidal activity, reducing larval weight gain and causing mortality.

Four compounds, including noreugenin, were identified as potentially responsible for the observed bioactivity.

Abstract

Studying plants with insecticidal activity and the compounds responsible for this type of activity is a promising approach for discovering new insecticides. Plants from the Meliaceae family are rich in limonoids, compounds with proven insecticidal action against certain pests. This study investigated the insecticidal activity of the crude methanolic extracts from Trichilia hirta fruits against Spodoptera frugiperda larvae. An initial toxicity bioassay showed 100% larval mortality when testing T. hirta extract. The crude extract was partitioned using ethyl acetate, dichloromethane, and n‐butanol, and the LD50 dose (785.244 mg kg−
1) was used to test the solvent fractions against the larvae. The ethyl acetate fraction caused the highest mortality and reduced larval weight gain. This fraction was subjected to column chromatography, yielding 12 fractions, of which, fractions 5 to 9 inhibited larval weight gain and caused mortality. LC‐ESI‐HRMS/MS analysis of the ethyl acetate fraction enabled the identification of four compounds: (1) noreugenin, (2) methyl 6,11β‐dihydroxy‐12α‐(2‐methylpropanoyloxy‐3,7‐dioxo‐14β, 15β‐epoxy‐1,5‐meliacadien‐29‐oate, (3) hirtinol A, and (4) 5α‐androstane‐3β,17β‐diol. This is the first study to report the presence of noreugenin in this plant genus. Future studies will be carried out to isolate other substances with promising insecticidal activities.

Fruits of Trichilia hirta were extracted and fractionated according to solvent polarity. The resulting partitions were screened for insecticidal activity by evaluating larval mortality and weight after 7 and 14 days. LC‐MS analysis of the most active fraction enabled the annotation of secondary metabolites potentially associated with the observed bioactivity.

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