The major indole alkaloid N,β-D-glucopyranosyl vincosamide from leaves of Psychotria leiocarpa Cham. & Schltdl. is not an antifeedant but shows broad antioxidant activity.
N,β-D-glucopyranosyl vincosamide (GPV), a major alkaloid of Psychotria leiocarpa, constitutes up to 2.5% of the dry weight in leaves. Alkaloid content was not elicited by mechanical wounding or jasmonate. At concentrations found in natural conditions or 2.5 fold higher, GPV did not inhibit herbivory in two unrelated generalist models (Helix aspersa and Spodoptera frugiperda) or in a specific interaction model (Heliconius erato fed with Passiflora suberosa). In situ staining assay showed quenching activity of hydrogen peroxide by GPV. Exposure of P. leiocarpa to acute UV-B stress did not change GPV or chlorophyll content, indicating high tolerance to this stress by the species. In vitro antioxidant tests against singlet oxygen, superoxide anions and hydroxyl radicals showed efficient quenching activity of the alkaloid. GPV was not effective as antifeedant, but it may act indirectly in P. leiocarpa protection against oxidative stress generated upon wounding, UV exposure and perhaps other environmental stresses.
Plant Physiology Laboratory, Center for Biotechnology and Department of Botany, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
Hélio Nitta
HN
Matsuura
Arthur Germano
AG
Fett-Neto
D000975:Antioxidants / Q000737:chemistry*; D005947:Glucose / Q000031:analogs & derivatives* / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D026121:Indole Alkaloids / Q000737:chemistry*; D018384:Oxidative Stress; D018515:Plant Leaves / Q000737:chemistry*; D032069:Psychotria / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry; D013481:Superoxides / Q000737:chemistry
D000975:Antioxidants; D026121:Indole Alkaloids; C483219:N,beta-D-Glucopyranosyl vincosamide; D013481:Superoxides; D026082:Singlet Oxygen; D017665:Hydroxyl Radical; D005947:Glucose