Abstract
Three undescribed bicyclo[3.2.1]octanoid neolignan glucosides, along with a known neolignan, were isolated from the leaves of Piper crocatum Ruiz & Pav. Their chemical structures were elucidated using extensive spectroscopic analyses including 1D and 2D NMR experiments and HR-ESI-MS analysis, as well as through comparison with previously reported data. Two compounds were assessed for their inhibitory effect against pyruvate dehydrogenase E1α S300 phosphorylation. The fluorescent image suggested that both compounds (60 µM) revealed a stronger inhibition effect than the positive control (dichloroacetate, DCA 5 mM), with IC50 values of 99.82 µM and 80.25 µM, respectively.
Highlights
The genus Piper belongs to the Piperaceae family, considered as one of the largest genera among angiosperms and one of the most abundant species in tropical forests [1]
The bicyclo[3.2.1]octanoid neolignans constitute a significant category of neolignan compounds, which were classified as the guianin- and macrophyllin-type
Among the known bicyclo[3.2.1]octanoid neolignans, the later type neolignans are less common than the former one
Summary
The genus Piper belongs to the Piperaceae family, considered as one of the largest genera among angiosperms and one of the most abundant species in tropical forests [1]. The connection between aromatic ring, glycosyl group, and bicyclo[3.2.1]octane of compound 1 was unambiguously assigned based on HMBC spectra (Figure 2). The correlation between H-1” (δH 4.84) and 145.2 (C-3) indicated that the glycosyl group was attached at C-7 of the aromatic ring These data led to the identification of a guianin-type 7.1 ,8.3 -connected neolignan skeleton of compound 1. The correlation between H-1′′ (δH 4.84) and 145.2 (C-3) indicated that the glycosyl group was attached at C-7 of4tohf e9 aromatic ring The HMBC correlations further confirmed these connections among the bicyclooctane moiety through colo1 -OMe (δH 3.34)/C-1 (δC 86.2), which indicated the deshielding effect of C-1 (δC 86.2) compared with the other three compounds. The adjacent torsion angles were measured by Chemdraw 3D (version 17.1)
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