Acylated Lignans Isolated from Brachanthemum gobicum and Their Trypanocidal Activity

Abstract

Eight isovaleryllignans (1−4 and 8−11), three isovalerylphenylpropanoids (5−7), three known lignans (12− 14), and four known compounds were isolated from an extract of the aerial part of Brachanthemum gobicum. The structures of the isolated compounds were elucidated based on NMR and MS data analyses. The enantiomers of compounds 1−3, 5, 8, and 9 were isolated using chiral-phase HPLC, and the absolute configurations of 1a/1b−3a/3b, 5a/5b, 8a/8b, and 9a/9b were elucidated from their optical rotations and ECD spectra; the other lignans were assumed to be racemic or scalemic by chiralphase HPLC analyses and optical rotation data. Some of the acylated lignans (racemic mixtures) (1−4, 8, 9, and 12−14) exhibited moderate inhibitory activities against Trypanosoma congolense, the causative agent of nagana disease in animals.

Biological activity evaluations of chemical constituents derived from Mongolian medicinal forage plants and their applications in combating infectious diseases and addressing health problems in humans and livestock

“…4), which was confirmed by the experiments that were conducted using pure samples during an investigation of the chemical constituents from Calligonum mongolicum of the family Polygonaceae [46]. Brachanthemum gobicum is used to remove external parasites, such as the parasitic louse Linognathus, from domesticated sheep [33]. The characteristic acylated lignans have an isovaleryl moiety, which is released by the disassembly of the compounds.…”

“…Characteristic acylated lignans were isolated from Brachanthemum gobicum (Asteraceae). They were isolated as pairs of enantiomers and their absolute configurations were determined from their optical rotations and electronic circular dichroism (ECD) spectra [33]. These Brachanthemum phenylpropanoid dimers (6-10, Fig.…”

“…Brachanthemum gobicum have isovaleryl moieties in lignans [33], and isovaleric acid is easily released by their hydrolysis. Although B. gobicum are known as desirable forage plants for camels in spring and autumn [20,21], humans perceive isovaleric acid as having a strong unpleasant odor.…”

Natural Enantiomers: Occurrence, Biogenesis and Biological Properties

“…configs. being determined by comparing the ECD and specific optical rotation data with those of (−)-lucidenal [34]. The plausible biosynthetic pathway of 39 was also proposed as shown in Scheme 1, with the nonstereospecific free radical coupling being the key factor to generate enantiomers.…”

“…Benzofuran-type lignan enantiomer pairs 42−44, 45 and 46 were discovered from Jatropha integerrima in 2015 [39], Brachanthemum gobicum in 2018 [34] and Picrasma quassioides in 2018 [40], respectively. The 7,8-trans configurations for 42−46 were determined by the large J 7,8 values (7.5 Hz for 42−45 in CDCl 3 , and 6.7 Hz for 46 in DMSO-d 6 ) and NOE analyses, while the abs.…”