Synthesis and structure-activity relationship of oleanolic mono- or di-glycosides against Magnaporthe oryzae

Abstract

ABSTRACT. Saponins are naturally-occurring units with broad diversity and are usually recognized as phytoanticipins. In order to develop new saponin chemical entities with high activity against Magnaporthe oryzae, we selected oleanolic acid (OA), which has wide natural distribution and rich content in plants. We used the ability of OA to act as an aglycone for glycosylation to obtain information on the structure-activity relationship (SAR) for rational molecular pesticide design. Oleanolic mono-or di-glycosides were synthesized at either the C 3 -hydroxy and/or C 28 -carboxyl position, using trichloroacetimidate or glycosyl bromide donors, respectively. Structures were confirmed by [1 H]-,[13 C]-NMR. Furthermore, the activity of the synthesized glycosides against M. oryzae was assessed in vitro, based on the mycelium growth rate. The twenty five oleanolic mono-or di-glycosides 2 G. Huo et al. Genetics and Molecular Research 15 (3): gmr.15038998 comprised fourteen saponins with 3-monosaccharide residue 1a-1n, six saponins with 28-monosaccharide residue 2a-2f, and five saponins with 3, 28-monosaccharide residue 3a-3e; all showed different activities against M. oryzae according to their different structures. We concluded that the optimal oleanolic mono-and di-glycoside structure for activity against M. oryzae is a C 3 connection of a hexose such as mannose, galactose, or glucose, in combination with a C 28 connection to a small group such as allyl or a C 3 connection to a pentose accompanied by a larger group such as another pentose or heptenyl at C 28 .

Design and Properties of Novel Hydrophobic Natural Tea Saponin and Its Organogels

“…Huo et al used the ability of oleanolic acid to act as an aglycone for glycosylation to design a pesticide. The activity of the synthesized glycosides against M. oryzae was assessed in vitro, based on the mycelium growth rate, and all showed different activities against M. oryzae according to their different structures [10]. The application of tea saponin modification has appeared in many fields, but there is no report related to the direct Gels 2024, 10, 225 2 of 14 preparation of organogels from modified tea saponin.…”