Evodialones A and B: Polyprenylated Acylcyclopentanone Racemates with a 3-Ethyl-1,1-diisopentyl-4-methylcyclopentane Skeleton from Evodia lepta

Abstract

Two polyprenylated acylcyclopentanone racemates, evodialones A (1) and B (2), featuring a 3-ethyl-1,1-diisopentyl-4-methylcyclopentane skeleton, were isolated from an extract of the aerial parts of Evodia lepta. Evodialone A (1) was resolved by chiral-phase HPLC to afford a pair of enantiomers, (+)- and (-)-evodialones A (1b/1a), while evodialone B (2) could not be resolved. Their structures were elucidated by spectroscopic analysis and a combination of computational techniques including gauge-independent atomic orbital calculation of 1D NMR data and experimental and TDDFT-calculated ECD spectra. A putative biosynthetic pathway of 1 and 2 starting from the monocyclic polyprenylated acylphloroglucinols is proposed. All the isolates were screened for the antimicrobial activity in vitro, and 1a and 1b showed moderate inhibitory activities against several pathogenic fungi with MICs values of 17.1-68.3 μM.

Isolation, Chiral-Phase Resolution, and Determination of the Absolute Configurations of a Complete Series of Stereoisomers of a Rearranged Acetophenone with Three Stereocenters

“…To define the absolute configurations of the individual enantiomers of 1 , the experimental ECD curves of (+)- 1 and (−)- 1 were compared with those calculated by using the time-dependent density functional theory (DFT) approach. As illustrated in Figure , the calculated ECD spectra of (3 R ,5 R ,16 R )- 1 and (3 S ,5 S ,16 S )- 1 agreed well with the experimental curves of (+)- 1 and (−)- 1 , respectively, which was consistent with reported data . The modified Mosher’s method was applied to confirm the absolute configuration of (−)- 1 . , Esterification of (−)- 1 with ( R )- and ( S )-α-methoxy-α-(trifluoromethyl)­phenylacetyl chloride (MTPACl) gave the corresponding (16 S )- and (16 R )-MTPA esters, respectively.…”

“…Their structures were identified as rearranged acetophenones having a prenylated acylcyclopentenone scaffold, by analysis of spectroscopic data (1D, 2D NMR) and comparison with literature values (Table S1, Supporting Information). The lack of optical activity and Cotton effects in the ECD spectrum indicated that 1 was racemic. Subsequently, 1 was resolved into two enantiomers, (+)- 1 and (−)- 1 , in a ratio of 1:1 by chiral-phase HPLC (Figure S14, Supporting Information).…”

“…The structures of 1 and 2 have been reported in a recent paper. However, 2 was reported as a racemate . The minor constituents 3 and 4 were also pursued in the present study and subjected to chiral-phase HPLC analysis.…”

Natural Enantiomers: Occurrence, Biogenesis and Biological Properties

“…configs. by a combination of modified Mosher's and TDDFT-ECD methods [200], while 423a/423b and 424 in racemic form had been previ-ously isolated from Evodia lepta by Tang et al in 2018 [201]. Also identified as rearranged acetophenones, compounds 427a/427b coupled with a phenylpropanoid fragment were isolated from Xanthostemon chrysanthus in 2019 [187].…”

Characterization, Antioxidant and Antitumor Activities of Oligosaccharides Isolated from Evodia lepta (Spreng) Merr. by Different Extraction Methods

“…In addition to its medicinal use, it has a long history being used as food, such as in Guangdong herbal tea [ 13 ]. The fat-soluble components of E. lepta [ 14 ], e.g., volatile oil, alkaloids, flavonoids, and coumarins, showed good anti-inflammatory [ 15 ], anti-viral [ 16 ], anti-bacterial [ 17 ], and antitumor [ 18 ] activities. Interestingly, the total sugar content of E. lepta is more than 30%, with oligosaccharides appearing to be the main active ingredients.…”