title: Phenolic Compounds and Their Fates In Tropical Lepidopteran Larvae: Modifications In Alkaline Conditions.
abstract: Lepidopteran larvae encounter a variety of phenolic compounds while consuming their host plants. Some phenolics may oxidize under alkaline conditions prevailing in the larval guts, and the oxidation products may cause oxidative stress to the larvae. In this study, we aimed to find new ways to predict how phenolic compounds may be modified in the guts of herbivorous larvae. To do so, we studied the ease of oxidation of phenolic compounds from 12 tropical tree species. The leaf extracts were incubated in vitro in alkaline conditions, and the loss of total phenolics during incubation was used to estimate the oxidizability of extracts. The phenolic profiles of the leaf extracts before and after incubation were compared, revealing that some phenolic compounds were depleted during incubation. The leaves of the 12 tree species were each fed to 12 species of lepidopteran larvae that naturally feed on these trees. The phenolic profiles of larval frass were compared to those of in vitro incubated leaf extracts. These comparisons showed that the phenolic profiles of alkali-treated samples and frass samples were similar in many cases. This suggested that certain phenolics, such as ellagitannins, proanthocyanidins, and galloylquinic acid derivatives were modified by the alkaline pH of the larval gut. In other cases, the chromatographic profiles of frass and in vitro incubated leaf extracts were not similar, and new modifications of phenolics were detected in the frass. We conclude that the actual fates of phenolics in vivo are often more complicated than can be predicted by a simple in vitro method.
authors.affiliation: Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20014, Turku, Finland. maviha@utu.fi.
authors.forename: Matti
authors.initials: M
authors.lastname: Vihakas
authors.affiliation: Zoological Museum, Department of Biology, University of Turku, FI-20014, Turku, Finland.
authors.forename: Isrrael
authors.initials: I
authors.lastname: Gómez
authors.affiliation: Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20014, Turku, Finland.
authors.forename: Maarit
authors.initials: M
authors.lastname: Karonen
authors.affiliation: Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20014, Turku, Finland.
authors.forename: Petri
authors.initials: P
authors.lastname: Tähtinen
authors.affiliation: Zoological Museum, Department of Biology, University of Turku, FI-20014, Turku, Finland.
authors.forename: Ilari
authors.initials: I
authors.lastname: Sääksjärvi
authors.affiliation: Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20014, Turku, Finland. j-p.salminen@utu.fi.
authors.forename: Juha-Pekka
authors.initials: JP
authors.lastname: Salminen
mesh_terms: D000818:Animals; D060434:Herbivory; D006863:Hydrogen-Ion Concentration; D007814:Larva / Q000737:chemistry / Q000378:metabolism; D007915:Lepidoptera / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D010636:Phenols / Q000032:analysis / Q000378:metabolism*; D010936:Plant Extracts / Q000737:chemistry / Q000378:metabolism*; D018515:Plant Leaves / Q000737:chemistry / Q000378:metabolism*; D010944:Plants / Q000737:chemistry / Q000378:metabolism*
chemical_list: D010636:Phenols; D010936:Plant Extracts
keywords: Amazonia; Faeces; MRM; Neotropical; Oxidation; Rain forest; SRM; UHPLC–DAD–MS