A novel diarylheptanoid bearing flavonol moiety from the rhizomes of Alpinia officinarum Hance

Diarylheptanoids from Rhizomes of Alpinia officinarum Inhibit Aggregation of α-Synuclein

Two new diarylheptanoids, alpinin A (1) and alpinin B (2), together with 18 known diarylheptanoids (3-20), were isolated from the rhizomes of Alpinia officinarum. Their structures were elucidated by comprehensive spectroscopic analysis, including high-resolution mass spectrometry, infrared spectroscopy, and one- and two-dimensional nuclear magnetic resonance spectroscopy. Structurally, alpinin A is a new member of the small family of oxa-bridged diarylheptanoids and contains the characteristic 2,6-cis-configured tetrahydropyran motif (C₁-C₅ oxa bridge). The absolute configuration of alpinin A was confirmed by asymmetric total synthesis of the enantiomer (ent-1), corroborating the assignment of the molecular structure. The absolute configuration of alpinin B was determined on the basis of the analysis of the circular dichroism exciton chirality spectrum. We evaluated the inhibitory activity of all isolated diarylheptanoids against α-synuclein aggregation at 10 μM. Alpinins A and B significantly inhibited α-synuclein aggregation by 66 and 67%, respectively.

An overview of chemical constituents from Alpinia species in the last six decades

Alpinia species is one of the most important genera of the Zingiberaceae family. Up to 2015, 544 compounds with various bioactivities were isolated, the major components are diarylheptanoids (143) and sesquiterpenoids (132).

A new dimeric diarylheptanoid from the rhizomes of Alpinia officinarum

AIM

To study the chemical constituents of the rhizomes of Alpinia officinarum Hance.

METHOD

Compounds were isolated by repeated column chromatography, and their structures were elucidated on the basis of spectral analysis. The cytotoxic activities of these compounds were evaluated with the T98G and B16F10 cell lines by the MTT assay.

RESULTS

A dimeric diarylheptanoid, named alpinin B (1), along with three known diarylheptanoids were obtained, and their structures were identified as alpinin B (1), 1, 7-diphenyl-3,5-heptanedione (2), (4E)-1, 7-diphenylhept-4-en-3-one (3) and (4E)-7- (4-hydroxyphenyl)-1-phenylhept-4-en-3-one (4).

CONCLUSION

Compound 1 is a new dimeric diarylheptanoid. The biosynthetic pathway of 1 was speculated to originate from a Michael reaction between compounds 2 and 3. Compound 3 showed cytotoxicity against the human glioblastoma T98G cell line with IC50 of 27 μmol·L(-1).

Naturally Occurring Diarylheptanoids

Diarylheptanoids, natural products with a 1,7-diphenylheptane structural skeleton, are mainly distributed in the roots, rhizomes and bark of Alpinia, Zingiber, Curcuma and Alnus species. They have become of interest in natural product research over the past twenty years because of their remarkable anticancer, anti-emetic, estrogenic, antimicrobial and antioxidant activity. This paper compiles all 307 naturally occurring diarylheptanoids from 46 plants as reported in 137 references with their distributions, physiological activities and 13C-NMR spectral data.