Butenolides, triterpenoids and phenylethanoid glycosides from Plantago depressa

doi:10.1016/j.phytol.2019.01.002

Phytochemistry Letters

Volume 30, April 2019, Pages 21-25

https://doi.org/10.1016/j.phytol.2019.01.002 Get rights and content

Highlights

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Twenty-nine compounds were obtained from the whole plants of Plantago depressa.
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Among them, four compounds are new.
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The structures were elucidated by comprehensive spectroscopic analyses.
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Some compounds showed anti-inflammatory and antiradical properties.

Abstract

Four new compounds, including two butenolides (1 and 2), an arborinane-type triterpenoid (3) and a phenylethanoid glycoside (4), along with the known triterpenoids (5–17) and phenylethanoid glycosides (18–29), were isolated from whole plants of Plantago depressa. The structures of the isolated compounds were elucidated by comprehensive spectroscopic analyses and were evaluated for their anti-inflammatory or antiradical activities. Our results underlined that, among compounds 1–17, only compound 16 inhibited lipopolysaccharide-induced NO production with an IC₅₀ equal to 5.33 ± 0.51 μM. All phenylethanoid glycosides (4, 18–29) were evaluated for their antiradical activity with a DPPH radical scavenging bioassay and showed high to moderate effect (IC₅₀ from 2.70 to 51.51 μM).

Graphical abstract

Twenty-nine compounds including four new ones of two butenolides, a triterpenoid and a phenylethanoid glycoside, were isolated from Plantago depressa. Selective compounds showed anti-inflammatory and antiradical activities.

Introduction

Plantago depressa Willd. is an herbal plant commonly found in Asia; both its seeds and the plant as a whole are used in China for traditional therapies, as they have a variety of medicinal properties, such as clearing internal heat and eliminating phlegm (Flora of China Editorial Committee of Chinese Academy of Sciences, 2002; National Pharmacopoeia Committee, 2015). P. depressa is rich in phenylethanoid glucosides (Yan et al., 2009; Feng et al., 2017), iridoid glucosides (Zhang et al., 1996; Sun et al., 2010) and polysaccharides (Olennikov et al., 2011), according to published reports. Our preliminary chemical investigation has revealed the presence of lipid constituents in the ethanolic extract of this plant, and a subsequent fractionation of the ethyl acetate sub-extract returned 19 fatty acid derivatives (Song et al., 2018). Apart from the abovementioned lipid molecules, an intensive study on the remaining fractions led to the separation and identification of two new butenolides (1 and 2), a new arborinane triterpenoid (3) and 13 known triterpenoid analogues (5–17) (Fig. 1). Additionally, the polar constituents in the n-BuOH partition were further investigated, and 13 phenylethanoid glycosides, including one new glycoside (4) and 12 known structurally related glycosides (18–29) (Fig. 1), were obtained. The structures of these compounds were elucidated by comprehensive spectroscopic analyses, and the absolute configuration of the sugar moiety in 4 was determined by chiral HPLC comparison of its hydrolysis derivatives with prepared standard samples. Some compounds showed anti-inflammatory and antiradical properties. Herein, this paper describes the isolation, structure characterization and biological evaluation of these natural products.

Section snippets

Results and discussion

Compound 1 was assigned the molecular formula of C₁₈H₃₀O₅ by (+)-HR-ESIMS analysis at m/z 349.1983 ([M + Na]⁺, calcd 349.1985), indicating four degrees of unsaturation. The ¹H NMR data (Table 1) revealed the presence of a methoxyl [δ_H 3.67 (s)], two methyl [δ_H 1.82 (s), 1.94 (s)], and ten methylene [δ_H 1.16 (1H, m), 1.32 (1H, m), 1.22–1.35 (12H, m), 1.61 (2H, m), 1.75 (1H, m), 1.97 (1H, m), 2.30 (2H, t, J = 7.5 Hz)] groups. The ¹³C NMR data (Table 1) showed signals of two carbonyl (δ_C 174.6,

General experimental procedures

IR spectra were recorded on an FT-IR VERTEX 70 instrument (Bruker BioSpin AG, Fremont, USA). Optical rotations were measured on a Rudolph VI polarimeter (Rudolph Research Analytical, Hackettstown, NJ, USA) with a 10 cm length cell. NMR experiments were recorded on a Bruker Avance DRX600 spectrometer (Bruker BioSpin AG, Fallanden, Switzerland) and referenced to residual solvent peaks (CD₃OD: δ_H 3.31, δ_C 49.00; CDCl₃: δ_H 7.26, δ_C 77.16). ESIMS analyses were carried out on an Agilent 1260–6460

Conflict of interest

The authors declare no conflict of interest.

Acknowledgements

Financial support from the Natural Science Foundation of Shandong Province (No. JQ201721), the Young Taishan Scholars Program (No. tsqn20161037) and Shandong Talents Team Cultivation Plan of University Preponderant Discipline (No. 10027) are greatly acknowledged. We also thank Prof. Jie Zhou for the identification of the plant materials and Elsevier Webshop for the language editing service.

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¹: These authors contributed equally.

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Butenolides, triterpenoids and phenylethanoid glycosides from Plantago depressa

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Results and discussion

General experimental procedures

Conflict of interest

Acknowledgements

Fitoterapia

Phytochemistry

Phytochemistry

Phytochemistry

Phytochemistry

Fitoterapia

Phytochemistry

In vitro antiprotozoal activity of triterpenoid constituents of Kleinia odora growing in Saudi Arabia

Molecules

Biologically active arborinane-type triterpenoids and anthraquinones from Rubia yunnanensis

J. Nat. Prod.

Study on separation and purification of phenylethanoid glycosides from Plantago herba by macroporous resin

Chin. J. Tradit. Chin. Med. Pharm.

The Flora of China

New arborane type triterpenoids from Rubia cordifolia var. pratensis and R. oncotricha

Chem. Pharm. Bull.

Triterpene acids from the leaves of Planchonella duclitan (blanco) bakhuizan

J. Chin. Chem. Soc.

A new 2,3-dimethyl butenolide from the brittle star Ophiomastix mixta

Chem. Pharm. Bull.

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Helv. Chim. Acta