Two New Phragmalin-Type Limonoids from Chukrasia tabularis var. velutina

Yi Li,Hui Li,Ling-Yi Kong,Jun Luo

doi:10.3390/molecules18010373

Abstract

Two new phragmalin-type limonoids with different structural skeletons, chuktabrin K (1) and tabulalin J (2), were isolated from the stem barks of Chukrasia tabularis var. velutina in the course of our ongoing research work in this area. Compound 1 was a 16-norphragmalin with an enolic alkyl appendage at C-15, and the carbonate moiety in 1 was also rare in natural organic molecules. The basic skeleton of compound 2 was a D-ring-opened phragmalin. Their structures were elucidated on HR-ESI-MS, 1H and 13C-NMR, HSQC, HMBC, and ROESY experiments.

Highlights

The stem barks of plants of the genus Chukrasia, traditionally used in Southern China to treat cold and fever [1], have been a research focus for natural products chemistry in recent years, and a series of phragmalin-type limonoids with novel and diverse structures have been isolated [2,3,4,5,6]
Further investigation on the phragmalin-type limonoids of this plant led to the isolation of two new phragmalin-type limonoids (Figure 1) with different structural skeletons
Their structures were elucidated on their extensive 1D and 2D spectroscopic analysis (HSQC, HMBC, and ROESY) and HR-ESI-MS

Summary

Introduction

The stem barks of plants of the genus Chukrasia, traditionally used in Southern China to treat cold and fever [1], have been a research focus for natural products chemistry in recent years, and a series of phragmalin-type limonoids with novel and diverse structures have been isolated [2,3,4,5,6]. In our previous research on limonoids from the stem barks of the title plant, many kinds of phragmalins with different skeletons were isolated, such as 16-norphragmalin with ketonic, enolic, or ketal alkyl appendages at. Chuktabrin K (1) was a rare 16-norphragmalin with enolic alkyl appendage at C-15, and the carbonate moiety in 1 is rare in natural organic molecules. Their structures were elucidated on their extensive 1D and 2D spectroscopic analysis (HSQC, HMBC, and ROESY) and HR-ESI-MS. Their isolation and structural elucidation are reported

Results and Discussion

General

Plant Material

Extraction and Isolation

Conclusions