Mulberry latex rich in antidiabetic sugar-mimic alkaloids forces dieting on caterpillars
Mulberry latex rich in antidiabetic sugar-mimic alkaloids forces dieting on caterpillars
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DOI：
10.1073/pnas.0506944103
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发表时间：
2006-01-31
影响因子：
11.1
通讯作者：
Kohno, K
中科院分区：
文献类型：
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作者：
Konno, K;Ono, H;Kohno, K
自古以来，桑叶（Morus spp.）就被用来养家蚕。由于蚕在桑叶上生长良好，桑叶对草食性昆虫的毒性和防御作用一直被忽视。在这里，我们展示了桑叶对除家蚕之外的其他毛毛虫有很高的毒性，因为乳胶的成分，一种从桑叶叶脉中渗出的乳白色汁液。当从桑叶中去除乳胶时，桑叶的毒性就消失了，含有乳胶的人工饲料显示出毒性。桑树乳胶含有非常高浓度的生物碱糖模拟糖苷酶抑制剂，据报道具有抗糖尿病活性，如1,4-二脱氧-1,4-亚胺-d -阿拉伯糖醇、1-脱氧诺吉霉素和1,4-二脱氧-1,4-亚胺-d -利比醇。在一些桑树品种中，乳胶中这些抑制剂的总浓度达到1.5-2.5%（干重8-18%），是以前报道的桑叶中这些抑制剂浓度的近100倍。这些糖模拟生物碱对毛虫有毒，但对家蚕没有毒性，表明家蚕可以绕过桑树的防御。我们的研究结果表明，乳胶成分在该树和其他植物抵御虫食中起着关键作用，这意味着植物乳胶是有用的药物和农药生物活性物质的宝库。
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 approximate to 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.