Pharmacological Activities and Phytochemicals of Etlingera pavieana (Pierre ex Gagnep) R.M.Sm

Abstract

Etlingera pavieana (Pierre ex Gagnep) R.M.Sm. (Zingiberaceae family) is commonly found in Southeast Asia. The rhizome of the plant is used as a spice and folk medicine in southeastern Thailand and Cambodia. The extracts, essential oil, and compounds from E. pavieana were found to possess a variety of pharmacological activities like anti-inflammatory, antioxidant, antiatherogenic, and antimicrobial effects. Furthermore, phytochemical studies have reported the presence of various chemical constituents, the main being phenylpropanoids such as trans-4-methoxycinnamaldehyde (MCD) and 4-methoxycinnamyl p-coumarate (MCC). Therefore, E. pavieana seems to be a potential source of natural products for treatment of various diseases and promotion of good health.

1. Introduction

Plant-based nutraceuticals or functional foods have gained attention due to their health promotion and safety in comparison to synthetic food ingredients [1, 2]. Presently, worldwide researchers have focus on scientific evaluation of medicinal plants to detect their pharmacological activities. Zingiberaceae family is distributed worldwide and comprises approximately 52 genera and 1587 species [3]. It is about 300 species belonging to 26 genera found in Thailand [4]. The plants in this family are the natural sources for traditional medicine, foods, spice, and other ethnobotanical uses [4]. Etlingera pavieana (Pierre ex Gagnep) R.M.Sm. is a member of the Zingiberaceae family and a medicinal plant of southeastern Thailand [5]. Several in vitro and in vivo pharmacological experiments and phytochemistry studies of E. pavieana have been reported. This chapter has presented comprehensive information about morphological characteristics, traditional uses, pharmacology activities, and phytochemical constituents of E. pavieana, which provide the data to plan future studies.

2. Botanical description and uses of Etlingera pavieana (Pierre ex Gagnep) R.M.Sm.

E. pavieana is endemic to Southeast Asia including Thailand, Cambodia, Laos, and Vietnam. This plant is locally known in Thai as rew-hom/raew hawm [5]. It is a perennial rhizomatous herb. The leafy shoots can grow to a height of 1–2.5 m (Figure 1A). The leaves are narrowly obovate, green, and glabrous (Figure 1B). The rhizomes are long-creeping, slender (0.7–1.5 cm in diameter), and fragrant (Figure 1C). Inflorescence arises from the rhizomes and is partially embedded in the ground (Figure 1D). To date E. pavieana is found in the natural habitats and cultivated in fruit gardens in southeastern Thailand for commercial purposes as food and herbs [5]. The young shoots are eaten as a culinary vegetable, and the rhizomes are used as a spice, an ingredient in noodle soup “Moo Lieng,” and as medicines. The reported medicinal uses of the rhizomes are relieving fever and flatulence and helping the digestive system and diuresis [5, 6]. In Cambodia, the E. pavieana rhizome is boiled in water with Amomum verum Blackw. and sugar to make a drink as a tonic and as a medicine for relieving stomach disorder and pharyngitis [5].

Figure 1.

Etlingera pavieana (Pierre ex Gagnep) R.M.Sm. whole plant (A), leaves (B), rhizomes (C), inflorescence (D) (Photographed by Srisook, K).

3. Phytochemical constituents of E. pavieana

It has been recently reported that the investigation of rhizomes of Etlingera pavieana from Thailand resulted in isolation of an uncommon compound which is (E)-((E)-3-(4-methoxyphenyl)ally) 3-(4-hydroxyphenyl) acrylate or 4-methoxycinnamyl p-coumarate (MCC) (1) and a series of phenylpropanoids such as (E)-3-(4-methoxyphenyl)prop-en-1-amine (2), 3-(4-methoxyphenyl) prop-2-enal, or trans-4-methoxycinnamaldehyde (MCD) (3), (E)-4-methoxycinnamic acid (4), and (E)-1-methoxy-4-(3-methoxyprop-1-enyl) benzene (5) as shown in Figure 2 [7]. Moreover, Srisook et al. have reported the isolation of the bioactive compound 1 and its two precursors, (2E)-3-(4-methoxyphenyl)prop-2-en-1-ol or 4-methoxycinnamyl alcohol (MCA) (6) and (E)-3-(4-hydroxyphenyl)prop-2-enoic acid or p-coumaric acid (CM) (7), from the rhizome of E. pavieana by activity-guided isolation [8]. The other three common phenylpropanoids, (E)-4-methoxycinnamaldehyde (3), trans-anethole (8), and trans-methyl isoeugenol (9), were also extracted from the plant by Srisook and colleagues (unpublished data).

Figure 2.

Chemical structures of some phytochemicals from rhizomes and leaves of E. pavieana.

The essential oil investigation of rhizome of E. pavieana resulted in trans-anethole (8) (48.5%) and elemicin (10, 13.8%) as major compounds [9], while Srisook et al. have investigated that the hydrodistillation of leaves of E. pavieana yielded methyl chavicol (11) as the most predominant product (93%) (unpublished data).

4. Pharmacological activities of E. pavieana

It is reported that E. pavieana possess various pharmacological activities such as antioxidant [10, 11]; antimicrobial [7, 12]; anticancer against breast, cervix, liver, colon, and small cell lung cancer [7, 13]; and anti-inflammatory effects[8, 14, 15, 16]. The detailed information is shown below.

4.1 Anti-inflammatory effect

Inflammation is a complex biological response to pathogenic agents and chemical as well as physical stimuli to get rid of the stimulants [17]. Macrophages are inflammatory cells that are considered as the first line of defense against various stimuli [18]. Upon contact with injurious stimuli, macrophages are activated and produce a large amount of inflammatory mediators and cytokines such as reactive oxygen species (ROS), nitric oxide (NO), prostaglandins (PGs), tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1), IL-6, and IL-12 [19, 20, 21, 22, 23, 24]. It is well-known that excess and prolonged secretion of these mediators and cytokines has participated in the pathogenesis of a variety of inflammatory diseases such as inflammatory bowel diseases [25], osteoarthritis [26], cancer [23], multiple sclerosis [27], neurodegenerative diseases like Alzheimer’s disease and Parkinson’s disease [28, 29, 30], atherosclerosis, and cardiovascular diseases [24, 31, 32, 33]. Therefore, substances inhibiting the secretions of these mediators and cytokines may be used to treat or prevent a variety of inflammation-related diseases. Since some Zingiberaceae species including Curcuma comosa [34], Amomum tsao-ko [35], Kaempferia parviflora [36], Zingiber officinale [37], Alpinia officinarum [38], Alpinia pricei Hayata [39], and Alpinia katsumadai Hayata [40] exhibit anti-inflammatory effects in vitro and in vivo, Srisook and colleagues, therefore, designed the experiment to determine anti-inflammatory activity of E. pavieana using lipopolysaccharide (LPS)- induced inflammation in RAW 264.7 murine macrophage cell model. A 95% ethanol extract of E. pavieana rhizomes was successively fractionated with hexane and ethyl acetate which was evaluated for anti-inflammatory effect on macrophage cells by inhibiting the production of inducible nitric oxide synthase (iNOS)-catalyzed NO. The hexane, ethyl acetate, and water fractions of rhizomal ethanol extracts of E. pavieana displayed anti-inflammatory effect on macrophage cells. Among them, ethyl acetate fraction was the most potent fraction. Furthermore, activity-guided isolation of this fraction showed that the bioactive compounds were phenolic compounds including 4-methoxycinnamyl alcohol (MCA), trans-4-methoxycinnamaldehyde (MCD), 4-methoxycinnamyl p-coumarate (MCC), and p-coumaric acid (CM) [8].

Mankhong et al. reported that 4-methoxycinnamyl p-coumarate, as the most potent compound extracted from E. pavieana rhizomes, exhibited an inhibitory effect on the production of cyclooxygenase-2 (COX-2)-catalyzed PGE₂, NO, IL-1β, and TNF-α on LPS-stimulated RAW 264.7 murine macrophages with IC₅₀ values of 14.1 ± 2.3, 32.7 ± 4.7, 3.0 ± 0.5, and 26.8 ± 5.7 μM, respectively. MCC compound inhibited gene expression of iNOS, COX-2, IL-1β, and TNF-α in a concentration-dependent manner through downregulating NF-κB, PI3K/Akt, and AP-1 signaling pathways [14, 16]. Furthermore, MCC attenuated LPS-reduced COX-1 expression in LPS-stimulated RAW 264.7 macrophages. It suggests that MCC possesses anti-inflammatory activity with selective inhibitory effect on COX expression [14].

Recently, trans-4-methoxycinnamaldehyde, another compound isolated from E. pavieana rhizomes, suppressed the formation of NO and PGE₂ as well as the expression of their synthesizing enzymes, iNOS and COX-2, on LPS- and Pam3CSK4-induced RAW 264.7 cells. The IC₅₀ values of NO and PGE₂ inhibition were 49.9 ± 4.7 and 87.6 ± 5.6 μM, respectively. The mechanism underlying anti-inflammatory activity of MCD could be inactivation of NF-κB and JNK/c-Jun signaling pathways [15]. Moreover, MCD showed a significant anti-inflammatory activity in rat models of acute inflammation. It was evident from this study that MCD (3 mg/ear) reduced ethyl phenylpropiolate (EPP)-induced ear edema by 51.5% inhibition. The second animal model used in this study was carrageenan-induced paw edema. Rats were orally administrated with MCD at doses of 75, 150, and 300 mg/kg for 1 h before injection with carrageenan. MCD can significantly decrease paw edema in a dose-dependent manner at 1, 3, and 5 h after carrageenan stimulation. Since edema formation induced by EPP and carrageenan is attributed to a release of several inflammatory mediators [41, 42], it is implied that the mode of MCD anti-inflammatory action in vivo model is mediated in part by suppression of inflammatory mediators.

We also investigated anti-inflammatory effect of essential oil of E. pavieana leaves on LPS-induced RAW 264.7 macrophages. The essential oil of E. pavieana leaves at 25–100 μg/mL exhibited a concentration-dependent inhibition effect on NO production without significant cytotoxicity (Figure 3A). Incubation of cells with essential oil caused reduction of iNOS protein and mRNA expression (Figure 3B,C). The compound responsible for anti-inflammatory effect of essential oil of E. pavieana leaves might be methyl chavicol, a main phytoconstituent of this essential oil (unpublished data).

Figure 3.

The inhibitory effect of essential oil of E. pavieana leaves (EO) on LPS-induced NO production (A) and iNOS expression. RAW 264.7 cells were incubated with essential oil of E. pavieana leaves and LPS for 24 h for determination of NO production and iNOS protein as well as 9 h for mRNA expression. Supernatant was collected for the analysis of NO production by Griess reaction. Cells were lysed and determined for protein (B) and mRNA (C) expression by Western blot analysis and real-time RT-PCR, respectively. ^###p < 0.001 compared to unstimulated control cells, ^*p < 0.05, ^**p < 0.01, and ^***p < 0.001, was significantly different from LPS-stimulated cells. AG = cells treated with 50 μM aminoguanidine, an iNOS inhibitor.

4.2 Antiatherogenic effect

Atherosclerosis is a chronic inflammatory disorder which leads to cardiovascular diseases (CVDs) [43, 44]; it is a major cause of death in the world [24, 45]. Endothelial dysfunction is an early step in the development of atherosclerosis. It involves with reduced NO bioavailability, low-grade inflammation, and oxidative stress [44, 46, 47, 48]. The initiation of atherosclerotic lesion is influenced by the expression of cell adhesion molecules including vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) on the vascular surface of the endothelial cells resulting in recruitment of leukocytes into the vascular tissue [49]. Inhibiting the expression of ICAM-1 and VCAM-1 leads to reduction of leukocyte emigration and retardation of the development of atherosclerosis. Thus, the substance that inhibits the expression of these cell adhesion molecules may be considered as anti-atherosclerosis agent that prevents vascular inflammatory disorders.

The rhizomal ethanol extract of E. pavieana was assessed for its anti-vascular inflammatory effect in human umbilical vein endothelial cells (EA.hy926 cells). Endothelial activation is upregulated by various pro-inflammatory cytokines, including TNF-α secreted under inflammatory conditions. The E. pavieana extract inhibited TNF-α-induced expression of ICAM-1 and VCAM-1 protein and mRNA in a concentration-dependent manner. The inhibitory effect of the rhizome extract in endothelial cells is caused from interfering with the activation of NF-κB and JNK/c-Jun signaling pathways. Moreover, Akt activation by E. pavieana rhizome is associated with negative regulation of inflammation. This anti-vascular inflammatory activity was attributed in part due to the presence of the two most active phenolic compounds of which were 4-methoxycinnamyl p-coumarate and trans-4-methoxycinnamaldehyde [50].

It is believed that decrease in endothelium-derived NO, produced by endothelial NO synthase (eNOS), results in reduced NO bioavailability [44, 49]. Another study was carried out to demonstrate antiatherogenic effect of E. pavieana rhizome. EA.hy926 endothelial cells incubated with the ethanol extract of E. pavieana rhizome (12.5–200 μg/mL) caused increased NO level in a concentration-dependent manner. This induction might be partly mediated by the activation of eNOS enzyme via phosphorylation at Ser1177 [11].

4.3 Antioxidant effect

Accumulating evidences suggest that not only inactivation of eNOS enzyme but also increased superoxide level leads to the reduction in NO bioavailability [24, 49]. Superoxide anion is produced by the mitochondrial electron transport chain and several enzymes in the endothelial cells. Superoxide anion is then oxidized to hydrogen peroxide and other physiological reactive species such as hydroxyl radical and hypochlorous acid [44]. Moreover, it reacts with NO to form highly reactive peroxynitrite leading to eNOS dysfunction [24, 47]. Chronic inflammation is also closely associated with oxidative stress which generated excess ROS [24].

The hexane, ethyl acetate, and water fractions of ethanol extract of E. pavieana rhizomes have shown in vitro antioxidant effects, which are evaluated by various antioxidant activity assays including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, reducing power and ferrous ion chelating activity [10]. E. pavieana rhizomal extract has also been assayed, its ROS scavenging activity in EA.hy926 endothelial cells, using 2,7-dichlorodihydrofluorescein diacetate (H₂DCF-DA) probe. TNF-α markedly induced ROS formation, while the extract (25–100 μg/mL) concentration dependently inhibited ROS level [11]. Thus, the data indicate antioxidant effect of E. pavieana mediated in part by counteract with ROS.

4.4 Anticancer activity

A number of plant-derived compounds can prevent progression of cancer [51, 52] and possess anticancer activity [53]. The ethanol extract from E. pavieana rhizomes exhibits cytotoxic effect against several cancer cell lines such as breast adenocarcinoma MDA-MB-231, hepatoma HepG₂, cervical carcinoma HeLa, and C33A. The IC₅₀ values were ranging from 160 to 192 μg/mL, respectively. Trans-4-methoxycinnamaldehyde, an active compound isolated by cytotoxicity-guided isolation from E. pavieana rhizomes, has shown cytotoxic effects against C33A, colorectal carcinoma HCT116, MDA-MB-231, and HepG₂ with the IC₅₀ values of 34.3, 38.7, 39.3, and 40.7 μM, respectively [13]. Tachai and Nuntawong [7] reported that 4-methoxycinnamyl p-coumarate exhibited inhibitory activity on cell growth of human breast cancer (MCF7), human oral cavity cancer (KB), and human small cell lung cancer (NCI-H187) with IC₅₀ values of 25.1, 20.2, and 34.8 μM, respectively [7]. Essential oil from the rhizomes was found to have cytotoxic effect against NCI-H187 (IC₅₀: 31.7 μg/mL) [7].

4.5 Antimicrobial activity

Various solvent extracts of E. pavieana (ethanol, acetone, dichloromethane, ethyl acetate, petroleum ether, and hexane) were found to be active against Gram-positive bacteria (Bacillus cereus, B. subtilis, Staphylococcus aureus, Listeria monocytogenes) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Vibrio parahaemolyticus, and Salmonella typhimurium). Antimicrobial activity of leaves was higher than that of stem and rhizome [12]. Tachai and Nuntawong demonstrated that hexane, dichloromethane, and methanol extracts of E. pavieana rhizomes were inactive against Mycobacterium tuberculosis, while MCC exhibited its antimicrobial activity against M. tuberculosis with minimum inhibitory concentration at 50 μg/mL [7].

5. Conclusion

In this chapter, we have provided the information on botanical aspects, dietary and traditional uses, phytochemicals, and pharmacological activities of Etlingera pavieana which is distributed in Southeast Asia. The major active compounds are phenylpropanoids such as trans-4-methoxycinnamaldehyde, and 4-methoxycinnamyl p-coumarate. Its rhizomes exhibit anti-inflammatory, antioxidant, antiatherogenic, antimicrobial, and anticancer activities. The pharmacological activities reported here confirm therapeutic efficacy of E. pavieana rhizomes which might be developed into medicines or nutraceuticals for the treatment and prevention of various diseases, especially inflammation-related diseases. However, in vivo toxicology studies of E. pavieana rhizomes should be performed along with the clinical trials.

Acknowledgments

This work was financially supported by the Research Grant of Burapha University through the National Research Council of Thailand (Grant no. 10/2555, 43/2558, 44/2558, 75/2559, 76/2559, 151/2560) and by the Research Unit of Natural Bioactive Compounds for Healthcare Products Development. The authors are highly grateful to the Center of Excellence for Innovation in Chemistry (PERCH-CIC) and the Commission on Higher Education, Ministry of Education, Thailand.

Conflict of interest

The authors have no conflict of interest to declare.