Highly Oxygenated Limonoids and Lignans from Phyllanthus flexuosus

Abstract

Two new highly oxygenated limonoids, flexuosoids A (1) and B (2), and three new arylnaphthalene lignan glycosides, phyllanthusmins D–F (3–5), were isolated from the roots of Phyllanthus flexuosus, in addition to three known lignans, phyllanthusmin C, arabelline, and (+)-diasyringaresinol. Their structures were elucidated on the basis of detailed spectroscopic analysis and chemical methods. Compounds 1 and 2, two new decaoxygenated limonoids with a C-19/29 lactol bridge and heptaoxygenated substituents at C-1, C-2, C-3, C-7, C-11, C-17, and C-30, represent the second example of limonoids in the Euphorbiaceae family. Most of the isolates were tested for their antifeedant, anti-herpes simplex virus 1, and cytotoxic activities. The new limonoids 1 and 2 showed promising antifeedant activity against the beet army worm (Spodoptera exigua) with EC₅₀ values of 25.1 and 17.3 μg/cm², respectively. In addition, both of them displayed moderate cytotoxicity against the ECA109 human esophagus cancer cell line, along with the known lignan glycoside, phyllanthusmin C, with the IC₅₀ values of 11.5 (1), 8.5 (2), and 7.8 (phyllanthusmin C) μM, respectively.

Graphical Abstract

Two new highly oxygenated limonoids, flexuosoids A (1) and B (2), and three new arylnaphthalene lignan glycosides, phyllanthusmins D–F (3–5), were isolated from the roots of Phyllanthus flexuosus, along with three known lignans. Flexuosoids A (1) and B (2) showed promising antifeedant activity against the beet army worm (Spodoptera exigua) with EC₅₀ values of 25.1 and 17.3 μg/cm², respectively. In addition, both of them and the known lignan glycoside, phyllanthusmin C, displayed moderate cytotoxicity against the ECA109 human esophagus cancer cell line, with the IC₅₀ values of 11.5, 8.5, and 7.8 μM, respectively.