title: Mulberry latex rich in antidiabetic sugar-mimic alkaloids forces dieting on caterpillars.
abstract: Since ancient times, mulberry leaves (Morus spp.) have been used to rear the silkworm Bombyx mori. Because the silkworm grows well on mulberry leaves, the toxicities and defensive activities of these leaves against herbivorous insects have been overlooked. Here we show that mulberry leaves are highly toxic to caterpillars other than the silkworm B. mori, because of the ingredients of the latex, a milky sap exuded from mulberry leaf veins. The toxicity of mulberry leaves was lost when the latex was eliminated from the leaves, and artificial diets containing latex showed toxicity. Mulberry latex contained very high concentrations of alkaloidal sugar-mimic glycosidase inhibitors reported to have antidiabetic activities, such as 1,4-dideoxy-1,4-imino-D-arabinitol, 1-deoxynojirimycin, and 1,4-dideoxy-1,4-imino-D-ribitol. The overall concentrations of these inhibitors in latex reached 1.5-2.5% (8-18% dry weight) in several mulberry varieties, which were approximately 100 times the concentrations previously reported from whole mulberry leaves. These sugar-mimic alkaloids were toxic to caterpillars but not to the silkworm B. mori, indicating that the silkworm can circumvent the mulberry tree's defense. Our results suggest that latex ingredients play key roles in defense of this tree and of other plants against insect herbivory, and they imply that plant latexes are treasuries of bioactive substances useful as medicines and pesticides.
authors.affiliation: National Institute of Agrobiological Sciences, 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan. konno@affrc.go.jp
authors.forename: Kotaro
authors.initials: K
authors.lastname: Konno
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ono
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nakamura
authors.forename: Ken
authors.initials: K
authors.lastname: Tateishi
authors.forename: Chikara
authors.initials: C
authors.lastname: Hirayama
authors.forename: Yasumori
authors.initials: Y
authors.lastname: Tamura
authors.forename: Makoto
authors.initials: M
authors.lastname: Hattori
authors.forename: Akio
authors.initials: A
authors.lastname: Koyama
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Kohno
mesh_terms: D017485:1-Deoxynojirimycin / Q000494:pharmacology; D000470:Alkaloids / Q000737:chemistry*; D000821:Animal Feed; D000818:Animals; D001089:Arabinose / Q000494:pharmacology; D001681:Biological Assay; D012831:Bombyx; D002244:Carbon / Q000737:chemistry; D005247:Feeding Behavior / Q000187:drug effects*; D050113:Imino Furanoses / Q000494:pharmacology; D007313:Insecta; D007840:Latex / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D031625:Morus; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D010946:Plants, Medicinal / Q000737:chemistry; D012255:Ribitol / Q000031:analogs & derivatives / Q000494:pharmacology; D013402:Sugar Alcohols / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000470:Alkaloids; D050113:Imino Furanoses; D007840:Latex; D010940:Plant Proteins; D013402:Sugar Alcohols; C058137:1,4-dideoxy-1,4-iminoarabinitol; D017485:1-Deoxynojirimycin; D012255:Ribitol; D002244:Carbon; D001089:Arabinose