Phosphodiesterase 5 and Arginase Inhibitory Activities of the Extracts from Some Members of Nelumbonaceae and Nymphaeaceae Families

Abstract

The objectives of this study were (1) to investigate the effect of extracts from some plants in the families Nelumbonaceae and Nymphaeaceae on phosphodiesterase 5 (PDE5) and arginase, which have been used in erectile dysfunction treatment, and (2) to isolate and identify the compounds responsible for such activities. The characterization and quantitative analysis of flavonoid constituents in the active extracts were performed by HPLC. Thirty-seven ethanolic extracts from different parts of plants in the genus Nymphaea and Victoria of Nymphaeaceae and genus Nelumbo of Nelumbonaceae were screened for PDE5 and arginase inhibitory activities. The ethanolic extracts of the receptacles and pollens of Nelumbo nucifera Gaertn., petals of Nymphaea cyanea Roxb. ex G.Don, Nymphaea stellata Willd., and Victoria amazonica (Poepp.) Sowerby and the petals and receptacles of Nymphaea pubescens Willd. showed IC50 values on PDE5 of less than 25 μg/mL while none of the extracts showed effects on arginase. The most active extract, N. pubescens petal extract, was fractionated to isolate and identify the PDE5 inhibitors. The results showed that six flavonoid constituents including quercetin 3’-O-β-xylopyranoside (1), quercetin 3-methyl ether 3’-O-β-xylopyranoside (2), quercetin (3), 3-O-methylquercetin (4), kaempferol (5) and 3-O-methylkaempferol (6) inhibited PDE5 with IC50 values at the micromolar level.

Vasorelaxant and hypotensive effects of an ethanolic extract of Nymphaea pubescens and its main compound quercetin 3-methyl ether 3′-O-β-xylopyranoside

“…Moreover, the extract enhanced the effect of the NO donor but did not act itself as a direct sGC activator. Altogether, these results suggest that the phosphodiesterase inhibitory properties exhibited by the extract ( Panklai et al, 2023 ) may contribute to its relaxant effect, but the causal relationship has to be investigated in future studies. Regarding the effect of the extract on calcium fluxes, only extracellular calcium entry through ROCCs was weakly but significantly inhibited by the extract, without any effect on VOCC or intracellular calcium release from SR.…”

“…These data suggest that this compound is probably involved in the relaxant effect of the extract, but other compounds that remain to be identified are also involved. Of interest, our previous work demonstrated that the WL extract also contains, to a lesser extent, quercetin 3′-O-β-xylopyranoside, quercetin, 3-O-methylquercetin, kaempferol, and 3-O-methylkaempferol ( Panklai et al, 2023 ). Mechanistically, the main compound quercetin 3-methyl ether 3′-O- β -xylopyranoside shared with the extract the same effects on the NO-sGC-cGMP pathway and ROCCs but did not present an α 1 -receptor antagonistic effect.…”

“…However, whether N. pubescens extract induces such a favorable effect on endothelial NO production has never been investigated. Of note, our previous work revealed that the main compound of an ethanolic extract of flowers from N. pubescens is a quercetin derivative, quercetin 3-methyl ether 3′-O- β -xylopyranoside ( Panklai et al, 2022 ; Panklai et al, 2023 ). As quercetin is well-known to induce vasorelaxant effects through NO-dependent effects ( Maaliki et al, 2019 ; Ciumărnean et al, 2020 ; Chen and Zhang, 2021 ; Grosso et al, 2022 ), this main compound might contribute to a positive endothelial effect in N. pubescens .…”